Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
DETAILED OFFICE ACTION
Information Disclosure Statement
The Information Disclosure Statements (IDSs) submitted on April 12, 2024 and June 30, 2026 in compliance with the provisions of 37 CFR 1.97 have been considered by the examiner and made of record in the application file.
Claim Status
Claims 1-22 are pending in this application and are under examination in this Office Action. No claims have been allowed.
Priority
Applicant's claim for foreign priority to Israeli Patent Application No. 301,090, filed March 2, 2023, is acknowledged.
Drawings
The drawings are objected to as failing to comply with 37 CFR 1.84(p)(4) because reference character "506b" has been used in FIG. 5B to designate different parts. Specifically, FIG. 5B
applies reference character 506b to the mirror, the beam splitters, and the quantum measurement device. The same reference character must not be used to designate different parts. Further, paragraph [0096] identifies a plurality of quantum interconnect devices 506b and later refers to the "generated probe qubit 506b," while the probe qubit is otherwise identified as 504b. The drawings and corresponding description therefore do not consistently identify the elements of FIG. 5B. Appropriate correction is required. No new matter should be entered.
Corrected drawing sheets in compliance with 37 CFR 1.121(d) are required in reply to the Office action to avoid abandonment of the application. Any amended replacement drawing sheet should include all of the figures appearing on the immediate prior version of the sheet, even if only one figure is being amended. The figure or figure number of an amended drawing should not be labeled as "amended." If a drawing figure is to be canceled, the appropriate figure must be removed from the replacement sheet, and where necessary, the remaining figures must be renumbered and appropriate changes made to the brief description of the several views of the drawings for consistency. Additional replacement sheets may be necessary to show the renumbering of the remaining figures. Each drawing sheet submitted after the filing date of an application must be labeled in the top margin as either "Replacement Sheet" or "New Sheet" pursuant to 37 CFR 1.121(d). If the changes are not accepted by the examiner, the applicant will be notified and informed of any required corrective action in the next Office action. The objection to the drawings will not be held in abeyance.
Specification
The disclosure is objected to because of the following informalities. Appropriate correction is required.
Paragraph [0011]
recites "an encoded valued transmitted via the quantum interconnect link." The expression "encoded valued" is grammatically incorrect in context and appears to have been intended to recite "encoded value." Applicant is required to correct or clarify this terminology.
Paragraph [0051]
refers to "polarity" as the degree of freedom while the same paragraph immediately describes rectilinear, diagonal, and circular polarization bases and the remainder of the disclosure identifies polarization as the pertinent quantum degree of freedom. Applicant is required to correct or clarify whether "polarization" was intended.
Paragraph [0061]
refers to a "bi-refrigerant crystal," whereas paragraph [0039] refers to a "birefringent crystal" in describing the weak-measurement component. Applicant is required to correct the inconsistent terminology.
Paragraph [0068]
states that the quantum measurement processing device 116 may use one or more of "the sets of circuitry 301, 302, 303, 304, 212, 214, and/or 216." However, reference character 214 is identified elsewhere as the quantum encoding device and reference character 216 is identified as quantum output data, rather than circuitry. Applicant is required to correct the inconsistent characterization and reference numerals.
Paragraph [0089]
refers to "processing circuity (e.g., processing circuitry 212)." Applicant is required to correct the typographical error so that the terminology is internally consistent.
Paragraph [0092]
states that the quantum interconnect receiver 108 may "compare the received valued to the transmitted value." Applicant is required to correct or clarify whether "received value" was intended.
Paragraph [0096]
first identifies the probe qubit as 504b, but subsequently refers to the "generated probe qubit 506b." Reference character 506b is otherwise used for the quantum interconnect/quantum measurement device in the same paragraph and in FIG. 5B. Applicant is required to correct the inconsistent reference character so that the written description and drawings correspond to one another.
Claim Objections
Claim 8 is objected to because of the following informality. Claim 8 recites "to obscure an eavesdropper's ability to identify an encoded valued transmitted via the quantum interconnect link." The expression "encoded valued" is grammatically incorrect in context and appears to have been intended to recite "encoded value." Appropriate correction is required.
Double Patenting
The nonstatutory double patenting rejection is based on a judicially created doctrine grounded in public policy (a policy reflected in the statute) so as to prevent the unjustified or improper timewise extension of the "right to exclude" granted by a patent and to prevent possible harassment by multiple assignees. A nonstatutory double patenting rejection is appropriate where the conflicting claims are not identical, but at least one examined application claim is not patentably distinct from the reference claim(s) because the examined application claim is either anticipated by, or would have been obvious over, the reference claim(s). See, e.g., In re Berg, 140 F.3d 1428, 46 USPQ2d 1226 (Fed. Cir. 1998); In re Goodman, 11 F.3d 1046, 29 USPQ2d 2010 (Fed. Cir. 1993); In re Longi, 759 F.2d 887, 225 USPQ 645 (Fed. Cir. 1985); In re Van Ornum, 686 F.2d 937, 214 USPQ 761 (CCPA 1982); In re Vogel, 422 F.2d 438, 164 USPQ 619 (CCPA 1970); and In re Thorington, 418 F.2d 528, 163 USPQ 644 (CCPA 1969).
A timely filed terminal disclaimer in compliance with 37 CFR 1.321(c) or 1.321(d) may be used to overcome an actual or provisional rejection based on nonstatutory double patenting provided the reference application or patent either is shown to be commonly owned with the examined application, or claims an invention made as a result of activities undertaken within the scope of a joint research agreement. See MPEP § 717.02 for applications subject to examination under the first inventor to file provisions of the AIA as explained in MPEP § 2159. A terminal disclaimer must be signed in compliance with 37 CFR 1.321(b).
The filing of a terminal disclaimer by itself is not a complete reply to a nonstatutory double patenting (NSDP) rejection. A complete reply requires that the terminal disclaimer be
accompanied by a reply requesting reconsideration of the prior Office action. Even where the NSDP rejection is provisional, the reply must be complete. See MPEP § 804, subsection I.B.1. For a reply to a non-final Office action, see 37 CFR 1.111(a). For a reply to final Office action, see 37 CFR 1.113(c). A request for reconsideration, while not provided for in 37 CFR 1.113(c), may be filed after final for consideration. See MPEP §§ 706.07(e) and 714.13.
The USPTO Internet website contains terminal disclaimer forms which may be used. Please visit www.uspto.gov/patent/patents-forms. For more information about eTerminal Disclaimers, refer to www.uspto.gov/patents/apply/applying-online/eterminal-disclaimer.
Related copending application. Application No. 19/559,349, published July 9, 2026 as US 2026/0197345 A1, is a continuation of Application No. 18/221,007. Application No. 19/559,349 identifies the same applicants, Mellanox Technologies, Ltd. and Bar-Ilan University, and names the same inventive entity (Tali Septon, Elad Mentovich, Moshe B. Oron, Yonatan Piasetzky, Yuval Idan, Eliahu Cohen, Avshalom C. Elitzur, and Taylor Lee Patti) as the instant application.
Accordingly, the claims of the copending continuation are properly considered for provisional nonstatutory double patenting.
For the obviousness analysis below, the copending application claims are the primary reference claims. Consistent with MPEP § 804, II.B.3, the specification of US 2026/0197345 A1 is consulted only to construe the scope of those claims and is not treated as prior art. The secondary references expressly relied upon below are Troupe, Farinholt et al., Johnson et al., Flament et al. (WO 2022/086634 A2), and Elliott; each was publicly available before the effective filing date of the instant claimed invention and is used only for the additional teachings identified. See MPEP § 804, II.B.3.
The published reference claims confirm the claim scope relied upon in this rejection. US 2026/0197345 A1 claim 1 recites determining a received state of a qubit, accessing the transmitted state of that qubit, comparing the received-state properties with the transmitted-state properties, and detecting a condition of the quantum communication link based on that comparison. Claim 14 additionally recites a plurality of qubits and comparison of received encoded values with transmitted encoded values from a subset of the received qubits. Claim 15 recites the corresponding computer-program-product implementation on at least one non-transitory computer-readable storage medium. [US 2026/0197345 A1, pp. 13-14, claims 1, 14-15].
For claim-construction purposes only, the portions of the reference specification that describe subject matter falling within the scope of those claims further explain that the received/transmitted-state properties may include polarization, phase, position, time of arrival, spin, or orbital momentum; that transmitted-state characteristics may be supplied through communication network 104 or a common database; that received and transmitted state properties are compared to detect a condition of the quantum communication link; and that the subset comparison uses received and transmitted encoded values. These passages are relied upon only to construe the reference claims and not as prior art. [US 2026/0197345 A1, pp. 9-10, ¶¶ [0066], [0069]-[0071], [0075]; FIG. 3].
Claims 1-6, 9-14, and 16-21 are provisionally rejected on the ground of nonstatutory double patenting as being unpatentable over claims 1-20 of copending Application No. 19/559,349 (US 2026/0197345 A1) in view of Troupe (U.S. Patent No. 9,306,739 B1), Farinholt et al. (U.S. Patent Application Publication No. 2022/0329417 A1), and Johnson et al. (U.S. Patent No. 10,014,934 B2) as applicable. Although the claims at issue are not identical, they are not patentably distinct from each other because of the following:
With respect to claim 1, claims 1 and 14 of Co-Pending Application No. 19/559,349 contain the following substantially overlapping limitations, shown underlined below:
Instant application
Co-Pending Application No. 19/559,349
As per claim 1, A method for communicating on a quantum interconnect link, the method comprising: receiving a subset of quantum particles of a plurality of quantum particles transmitted on the quantum interconnect link; wherein the subset of quantum particles is transmitted having a transmitted physical condition comprising one or more selected physical observables imparted to the subset of quantum particles within each of a first set of one or more quantum degrees of freedom; wherein each of the first set of one or more quantum degrees of freedom are coupled to a second set of one or more quantum degrees of freedom comprising one or more coupled observables, and wherein each of the coupled observables are indirectly imparted by imparting the one or more selected observables to the subset of quantum particles; determining a received physical condition of the subset of quantum particles, wherein the received physical condition comprises received observables of each of the second set of one or more quantum degrees of freedom upon receipt of the subset of quantum particles; accessing data reflecting the transmitted physical condition, wherein the data reflecting the transmitted physical condition reflects the imparted one or more selected observables and an indication of the one or more coupled observables; comparing the received physical condition with the transmitted physical condition; and upon detecting a difference between the received observables and the coupled observables, generating a notification of interference along the quantum interconnect link.
As per claim 1, A quantum communication method comprising: determining a received state of a qubit received via a quantum communication link, wherein the received state comprises one or more properties of the received qubit; accessing a transmitted state of the qubit, wherein the transmitted state comprises one or more properties of the qubit as transmitted; comparing the one or more properties of the qubit in the received state with the one or more properties of the qubit in the transmitted state; and detecting a condition of the quantum communication link based on the comparison between the received state and the transmitted state.As per claim 14, a plurality of qubits are received each having a transmitted encoded value according to a transmitted basis vector; determining a received encoded value; comparing the received encoded value with the transmitted encoded value from a subset of the received qubits; and detecting the condition of the quantum communication link based on the comparison.
The features of claim 1 of the current application that are not expressly recited in claims 1 and 14 of Co-Pending Application No. 19/559,349 include:
"the first set of one or more quantum degrees of freedom are coupled to a second set of one or more quantum degrees of freedom comprising one or more coupled observables," "each of the coupled observables are indirectly imparted by imparting the one or more selected observables," "accessing data reflecting the transmitted physical condition, wherein the data reflecting the transmitted physical condition reflects the imparted one or more selected observables and an indication of the one or more coupled observables," and "generating a notification of interference along the quantum interconnect link."
With respect to the additional data-content limitation, reference claim 1 already requires accessing a transmitted state of the qubit comprising one or more properties of the qubit as transmitted, and reference claim 14 further requires a transmitted basis vector and transmitted encoded value for the subset comparison. Troupe supplies the corresponding classical preparation/measurement metadata by broadcasting Alice's encoding-basis list P and raw-key list R together with Bob's measurement-basis list M and associated unitary information used to select and evaluate the weak observable. Farinholt supplies the configured physical relationship between the selected encoded observable and the auxiliary pointer observable, including polarization encoding with the temporal degree of freedom as the pointer and phase encoding with polarization as the pointer. Thus, the accessed transmitted-state data identify the imparted selected observable and, together with the known configured coupling, provide the indication of the associated coupled/pointer observable required by the instant claim. [US 2026/0197345 A1, claims 1 and 14; Troupe, col. 11, ll. 1-45; Farinholt, ¶¶ [0142]-[0144]; FIG. 11].
However, in analogous art, Troupe expressly teaches the coupled-degree-of-freedom implementation. Troupe teaches that implementation of the weak measurements "can be accomplished by weakly coupling another observable of each photon to the particular observable used to encode the key in the BB84 protocol," and explains that for phase encoding the photon polarization may be used as the weak-measurement pointer, and vice versa for polarization encoding. [Troupe, col. 22, lines 20-36].
Farinholt provides a concrete implementation of the same known coupling principle. Farinholt teaches that the raw key information may be encoded in photon polarization while the photon's time degree of freedom is used as the weak-measurement pointer, with the weak coupling implemented by a polarizing interferometer and small relative optical delay. [Farinholt, p. 16, ¶¶ [0142]-[0144]; FIG. 11].
Johnson expressly teaches the missing notification step. Johnson et al. teach that when eavesdropping is detected, “an alarm notifies the end-user of the intrusion,” and also teach interruption or rerouting as alternative responses. [Johnson, col. 11, ll. 5-10; FIG. 5c.]
Accordingly, the primary reference claims and the secondary references teach all of the limitations of claim 1.
The combination is achieved by using the known weak-measurement auxiliary/coupled degree of freedom taught by Troupe and Farinholt within the received-state/transmitted-state comparison method claimed in Application No. 19/559,349, and by providing the known alarm/notification response taught by Johnson when the comparison reveals interference. Each element would continue to perform its established function: the auxiliary degree of freedom supplies a minimally disturbing probe of the transmitted quantum state, the received/transmitted comparison detects a channel condition, and the alarm communicates the detected interference.
Therefore, the results would have been predictable to one of ordinary skill in the art. Based on the above findings, it would have been obvious to one of ordinary skill before the effective filing date of the instant claimed invention to employ the coupled weak-measurement pointer and notification teachings within the method claimed in Application No. 19/559,349 as no more "than the predictable use of prior-art elements according to their established functions."
With respect to claim 9, claim 1 of Co-Pending Application No. 19/559,349 provides the same received-state/transmitted-state comparison function, while Farinholt provides the known receiver apparatus implementation, as shown below:
Instant application
Co-Pending Application No. 19/559,349
As per claim 9, An apparatus for communicating on a quantum interconnect link, comprising: a probe coupled with the quantum interconnect link, wherein the probe is configured to receive a subset of quantum particles of a plurality of quantum particles transmitted on the quantum interconnect link; wherein the probe is configured to measure selected observables in a first set of quantum degrees of freedom and one or more coupled observables in a second set of quantum degrees of freedom; communication circuitry configured to access a transmitted physical condition; and processing circuitry configured to determine a received physical condition; compare the received physical condition with the transmitted physical condition; and upon detecting a difference, generate a notification of interference.
As per claim 1, A quantum communication method comprising: determining a received state of a qubit received via a quantum communication link; accessing a transmitted state of the qubit; comparing the properties of the qubit in the received state with the properties in the transmitted state; and detecting a condition of the quantum communication link based on the comparison.Farinholt et al., claim 1, recites a QKD receiver having a polarized beam splitter, an orthogonal pair of photon detectors, an apparatus for performing a weak measurement, a broadcaster, an error-rate estimator, and a post-processor.
The features of claim 9 not expressly recited in claim 1 of Application No. 19/559,349 are the apparatus-form implementation, the coupled first/second quantum degrees of freedom, and the explicit notification of interference.
Farinholt supplies the apparatus implementation by expressly claiming a QKD receiver containing the detector/weak-measurement/broadcast/error-estimation hardware.
Troupe supplies the coupled-observable implementation for the same photon, and Johnson et al. supply the alarm/notification response upon detection of eavesdropping.
One of ordinary skill in the art would have been motivated to embody the claimed received/transmitted-state comparison of Application No. 19/559,349 in the known QKD receiver hardware of Farinholt because the primary claim necessarily operates on received quantum states and Farinholt provides a conventional apparatus for performing the required weak measurements, broadcasting results, and estimating channel error.
Adding Troupe's coupled observable and Johnson's alarm would have predictably allowed that receiver to probe an auxiliary degree of freedom and communicate a detected interference condition.
The combination does not change the principle of operation of any element and represents the predictable use of known QKD receiver components for their established functions.
For purposes of the provisional nonstatutory double patenting analysis only, and without withdrawing the 35 U.S.C. § 112(b) rejection below, claim 16 is interpreted consistently with claim 1 and the written description such that “interconnected observables” and “coupled observables” refer to the same auxiliary observables and such that the later recitation of “the second set of one or more subset of quantum particles” refers to the previously introduced second set of one or more quantum degrees of freedom. This interpretation is used solely to complete examination on the merits and does not cure the indefiniteness identified below.
With respect to claim 16, claim 15 of Co-Pending Application No. 19/559,349 recites the same computer-program-product architecture for received/transmitted comparison, as shown below:
Instant application
Co-Pending Application No. 19/559,349
As per claim 16, A computer program product for communicating on a quantum interconnect link, comprising at least one non-transitory computer-readable storage medium storing program instructions that, when executed, cause the computer program product to: receive a subset of quantum particles having a transmitted physical condition; determine a received physical condition comprising received observables of a second set of quantum degrees of freedom; access data reflecting the transmitted physical condition; compare the received physical condition with the transmitted physical condition; and upon detecting a difference between received observables and coupled observables, generate a notification of interference.
As per claim 15, A computer program product for quantum communications, comprising at least one non-transitory computer-readable storage medium storing program instructions that, when executed, cause the computer program product to: determine a received state of a qubit received via a quantum communication link; access a transmitted state of the qubit; compare the one or more properties of the qubit in the received state with the one or more properties of the qubit in the transmitted state; and detect a condition of the quantum communication link based on the comparison.
The only material differences are the same coupled-degree-of-freedom and notification limitations discussed for claim 1, together with the recitation of a subset/plurality. Application No. 19/559,349 further claims plural qubits and subset-based comparisons in claims 12-14. Troupe and Farinholt render the coupled auxiliary-degree-of-freedom limitation obvious for the reasons above, and Johnson et al. render the notification limitation obvious for the reasons above.
Accordingly, claim 16 is not patentably distinct from claim 15, considered with claims 12-14, of Application No. 19/559,349 in view of the cited secondary references. The computer-readable-medium form does not impart a patentable distinction where the same quantum-link
comparison operations are performed by stored program instructions, and the added coupled-pointer and notification functions are known, compatible, and predictable.
With respect to claims 3, 11, and 18, each claim additionally requires identifying the second quantum degree of freedom and determining the coupled/interconnected observable(s).
Troupe expressly teaches "weakly coupling another observable of each photon to the particular observable used to encode the key" and gives reciprocal phase/polarization pointer implementations. Farinholt further teaches polarization-encoded key information with the photon time degree of freedom used as the weak-measurement pointer. These teachings make identification and measurement of the second, coupled degree of freedom an ordinary implementation choice once the primary reference comparison method is used to detect weak-measurement disturbances.
With respect to claims 4, 12, and 19, each claim requires that the quantum degrees of freedom include one or more of polarization, time-of-arrival, spatial displacement, relative phase, orbital angular momentum, spatial modes, energy/frequency, quantized quadrature’s, and/or spin.
Co-Pending Application No. 19/559,349 expressly claims a time-of-arrival condition (claims 2, 7, 9, 11 and 16, 19-20) and a displacement/position condition (claims 3-6, 17-18). Because the instant dependent claims use the open phrase 'one or more of,' the expressly claimed time-of-arrival and displacement/position species fall within the scope of the instant listed genus. Troupe and Farinholt additionally teach polarization, phase, time, and pointer implementations. Thus, the added list does not patentably distinguish claims 4, 12, or 19.
With respect to claims 2, 10, and 17, each claim additionally requires a value representing one or more qudits.
Troupe expressly teaches that the weak-measurement strategy "could also be used to generalize the qubit protocols to higher-dimensional qudit two basis and complete MUB QKD protocols." [Troupe, col. 22, lines 50-60].
A person of ordinary skill applying the primary reference's quantum-state comparison technique would have found it obvious to use Troupe's expressly taught higher-dimensional qudit implementation because it is the same weak-measurement channel-characterization
technique applied to a known higher-dimensional quantum information unit. The expected result is the same detection/characterization function with more than two available states.
With respect to claims 5, 13, and 20, each claim additionally requires that the transmitted physical condition be received or accessed on a secondary communication channel separate from the quantum interconnect link.
Troupe teaches Alice and Bob communicating over an authenticated classical channel 140 separate from quantum channel 150 and publicly exchanging measurement/basis information. [Troupe, FIG. 1; col. 12-13].
Farinholt likewise teaches Bob publicly broadcasting the weak-measurement observable and corresponding results to Alice.
It would have been obvious to transmit or access the expected/transmitted physical condition over this known authenticated classical side channel because QKD protocols conventionally keep the quantum carrier channel separate from the classical basis/result exchange. Doing so permits the receiver to perform the claimed comparison without disturbing the quantum transmission and yields only the predictable result of using the classical channel for classical state-description data.
With respect to claims 6, 14, and 21, each claim additionally requires that the notification of interference indicate detection of an eavesdropper accessing the quantum interconnect link.
Troupe describes its BB84 weak-measurement procedure as a test for the presence of Eve and teaches that weak-measurement results are used to detect an eavesdropper.
Johnson expressly teaches that detected eavesdropping triggers an alarm notifying the end user of the intrusion. Thus, the dependent eavesdropper-notification limitation is the direct and predictable security use of the interference condition detected by the primary reference combination.
This is a provisional nonstatutory double patenting rejection.
For purposes of the provisional nonstatutory double patenting analysis of claims 15 and 22 only, and without withdrawing the 35 U.S.C. § 112(b) rejections below, claim 15 is treated as requiring the apparatus of claim 9 to be configured to perform the stated feedback transmission, and claim 22 is treated as requiring the stored program instructions of claim 16, when executed, to cause the stated feedback transmission. This treatment permits compact examination of the substantive limitations while preserving the separate indefiniteness rejections.
Claims 7, 15, and 22 are provisionally rejected on the ground of nonstatutory double patenting as being unpatentable over claims 1 and 15 of copending Application No. 19/559,349 (US 2026/0197345 A1) in view of Troupe, Farinholt et al., and Johnson et al. as applied above, and further in view of Flament et al. (WO 2022/086634 A2). Although the claims at issue are not identical, they are not patentably distinct from each other because of the following:
As per claims 7, 15, and 22,
The claimed subject matter further requires, upon detecting a difference between the received observables and the coupled observables, transmitting data reflecting the detected difference to the transmitting device to cause the transmitting device to adjust one or more transmission parameters to compensate for anomalies in the quantum interconnect link.
The primary reference combination teaches detecting a channel condition by comparing received and transmitted quantum-state properties, including discrepancies in position/time and other state characteristics, but does not expressly require using that detected difference as transmitter feedback for adjustment of subsequent transmissions.
However, in analogous art, Flament expressly teaches the missing feedback-compensation step.
Flament teaches determining a feedback parameter from measurements of probe-photon polarization, including based on the difference between initial polarization and final polarization, and using the feedback parameter to change a setting of a polarization modulator so as to change the polarization of subsequent quantum data photons. [Flament, claims 1, 15, and 24].
One of ordinary skill in the art would have been motivated to use the measured discrepancy produced by the primary reference comparison as the feedback quantity taught by WO 2022/086634 A2 because both address the same technical problem of quantum-link disturbances and both use measured differences in quantum-state properties to characterize non-ideal channel behavior. Applying the detected difference to a transmitter-side modulator for subsequent photons would predictably compensate drift/noise while retaining the same receive/compare architecture. The modification is no more than the use of a known feedback correction technique to correct the same measured channel anomaly according to its established function.
This is a provisional nonstatutory double patenting rejection.
Claim 8 is provisionally rejected on the ground of nonstatutory double patenting as being unpatentable over claim 1 of copending Application No. 19/559,349 (US 2026/0197345 A1) in view of Troupe and Johnson et al. as applied above, and further in view of Elliott (U.S. Patent No. 7,068,790 B1). Although the claims at issue are not identical, they are not patentably distinct from each other because of the following:
As per claim 8,
The method further requires, upon detecting a difference between the received observables and the coupled observables, remediating at least one irregularity on the quantum interconnect link to obscure an eavesdropper's ability to identify an encoded value transmitted via the quantum interconnect link.
The primary reference combination teaches detecting interference/eavesdropping from the received/transmitted comparison and generating an alarm/notification, but does not expressly require the particular remediation step recited in claim 8.
However, in analogous art, Elliott expressly teaches routing around an eavesdropper in a QKD network. Elliott claim 16 recites identifying eavesdropping on a first path using quantum cryptography and establishing a second path responsive to the eavesdropping identification, wherein the second path comprises a different route through the network, followed by transmitting data symbols over the second path. [Elliott, claim 16; see also Abstract].
Johnson independently reinforces the same remediation concept by teaching that, after eavesdropping is detected, data transmission may be interrupted or traffic rerouted to non-eavesdropped channels.
One of ordinary skill in the art would have been motivated to apply Elliott's known QKD rerouting/remediation to the interference detected by the primary reference combination because the purpose of detecting an eavesdropper is to preserve secrecy of the transmitted quantum information. Moving subsequent transmissions away from the compromised route, or otherwise interrupting/rerouting the traffic, predictably reduces the eavesdropper's ability to continue observing the encoded value.
The claimed remediation therefore represents the predictable security response to the already-detected eavesdropping condition.
This is a provisional nonstatutory double patenting rejection.
Claim Rejections - 35 U.S.C. § 112(b)
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION. —The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
Claims 15-22 are rejected under 35 U.S.C. 112(b) as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor, or for pre-AIA the applicant regards as the invention.
Regarding claim 15,
Claim 15 depends from apparatus claim 9 and recites that "the subset of quantum particles is transmitted by a transmitting device and the method further comprises, upon detecting a difference between the received observables and the coupled observables, transmitting data reflecting the detected difference to the transmitting device to cause the transmitting device to adjust one or more transmission parameters to compensate for anomalies in the quantum interconnect link."
There is a lack of antecedent basis for "the method" because claim 9 is directed to an apparatus and does not previously introduce a method to which "the method" can refer. Further, claim 15 begins as an apparatus claim but positively recites performance of the method step of "transmitting data reflecting the detected difference to the transmitting device." As written, it is unclear whether the claim is directed to the apparatus itself, to a method of operating the apparatus, or to an apparatus only when the recited transmitting step is actually performed. This creates uncertainty as to when the claim is satisfied and whether infringement would occur upon making or possessing the apparatus or only upon performance of the recited process step. Accordingly, the metes and bounds of claim 15 are not reasonably certain, and claim 15 is indefinite.
Regarding claim 16,
Claim 16 recites that "each of the first set of one or more quantum degrees of freedom are interconnected to a second set of one or more quantum degrees of freedom comprised of one or more interconnected observables," and then recites "wherein each of the coupled observables are indirectly imparted by imparting the one or more selected observables to the subset of quantum particles."
There is a lack of antecedent basis for "the coupled observables" because claim 16 previously introduces "interconnected observables," not "coupled observables." The difference in terminology is material because the later limitations of claim 16 repeatedly rely on "the coupled observables" when defining the data reflecting the transmitted physical condition and when determining whether a difference exists. As written, it is unclear whether
"Coupled observables" and "interconnected observables" refer to the same observables or to different observables.
Claim 16 further recites that the received physical condition "comprises received observables of each of the second set of one or more subset of quantum particles upon receipt of the subset of quantum particles." Earlier in claim 16, however, "the second set" is introduced as "a second set of one or more quantum degrees of freedom." The later phrase "the second set of one or more subset of quantum particles" changes the nature of the previously recited second set from quantum degrees of freedom to one or more subsets of quantum particles. As written, it is unclear whether the received observables are required for the previously recited second set of quantum degrees of freedom, for one or more subsets of quantum particles, or for some other intended subject matter. This ambiguity directly affects what must be determined and subsequently compared by the claimed computer program product. Accordingly, the metes and bounds of claim 16 are not reasonably certain, and claim 16 is indefinite.
Regarding claim 17,
Claim 17 depends from claim 16 and therefore incorporates all limitations of claim 16, including the indefinite recitations of "the coupled observables" and "the second set of one or more subset of quantum particles." Claim 17 merely adds that a value representing one or more qudits is encoded by imparting the selected observables and does not clarify or cure either ambiguity of claim 16. Accordingly, claim 17 is indefinite.
Regarding claim 18,
Claim 18 depends from claim 16 and therefore incorporates the indefinite limitations discussed above. Claim 18 further recites "determining one or more interconnected observables for each of the second set of one or more quantum degrees of freedom of the quantum particle."
There is a lack of antecedent basis for "the quantum particle." Claim 16 introduces "a plurality of quantum particles" and "a subset of quantum particles," but neither claim 16 nor claim 18 previously identifies a singular quantum particle to which "the quantum particle" can clearly refer. As written, it is unclear whether the recited interconnected observables are determined for each particle of the subset, for a particular selected particle, or for some other particle. Claim 18 also uses "interconnected observables" while the comparison and notification limitations incorporated from claim 16 rely on "coupled
observables," without clarifying whether these terms identify the same observables. Accordingly, the metes and bounds of claim 18 are not reasonably certain, and claim 18 is indefinite.
Regarding claim 19,
Claim 19 depends from claim 16 and therefore incorporates all limitations of claim 16, including the indefinite recitations of "the coupled observables" and "the second set of one or more subset of quantum particles." Claim 19 merely specifies examples of quantum degrees of freedom and does not clarify or cure the ambiguities of claim 16. Accordingly, claim 19 is indefinite.
Regarding claim 20,
Claim 20 depends from claim 16 and therefore incorporates all limitations of claim 16, including the indefinite recitations of "the coupled observables" and "the second set of one or more subset of quantum particles." Claim 20 merely recites that the transmitted physical condition is received on a secondary communication channel separate from the quantum interconnect link and does not clarify or cure the ambiguities of claim 16. Accordingly, claim 20 is indefinite.
Regarding claim 21,
Claim 21 depends from claim 16 and therefore incorporates all limitations of claim 16, including the indefinite recitations of "the coupled observables" and "the second set of one or more subset of quantum particles." Claim 21 merely recites that the notification of interference indicates detection of an eavesdropper accessing the quantum interconnect link and does not clarify or cure the ambiguities of claim 16. Accordingly, claim 21 is indefinite.
Regarding claim 22,
Claim 22 depends from computer program product claim 16 and recites that "the subset of quantum particles is transmitted by a transmitting device and the method further comprises, upon detecting a difference between the received observables and the coupled observables, transmitting data reflecting the detected difference to the transmitting device to cause the transmitting device to adjust one or more transmission parameters to compensate for anomalies in the quantum interconnect link."
Claim 22 incorporates the indefinite limitations of claim 16 and does not cure them. Claim 22 additionally lacks antecedent basis for "the method" because claim 16 is directed to a computer program product and does not previously introduce a method to which "the method" can refer. Further, claim 22 begins as a computer program product claim but positively recites performance of the method step of "transmitting data reflecting the detected difference to the transmitting device." As written, it is unclear whether the claim is directed to the computer program product itself, to a process performed by executing the stored program instructions, or to the computer program product only when the recited transmitting step is actually performed. This creates uncertainty as to when the claim is satisfied. Accordingly, the metes and bounds of claim 22 are not reasonably certain, and claim 22 is indefinite.
Accordingly, claims 15-22 are indefinite under 35 U.S.C. § 112(b).
Claim Rejections – 35 U.S.C. § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for the obviousness rejections set forth in this Office Action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
As reiterated by the Supreme Court in KSR, and as set forth in MPEP 2141 (R-01.2024), II, the factual inquiries of Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), applied for establishing a background for determining obviousness under 35 U.S.C. § 103, are summarized as follows:
Determining the scope and content of the prior art;
Ascertaining the differences between the prior art and the claims at issue;
Resolving the level of ordinary skill in the pertinent art; and
Considering objective evidence indicative of obviousness or non-obviousness, if present.
Prior-art status of the applied references. The references relied upon in the rejections below were publicly available before the March 2, 2023 effective filing date acknowledged above: Farinholt et al. (US 2022/0329417 A1) published October 13, 2022; Troupe (US 9,306,739 B1) issued April 5, 2016; Johnson et al. (US 10,014,934 B2) issued July 3, 2018; Flament et al. (WO 2022/086634 A2) published April 28, 2022; and Elliott (US 7,068,790 B1) issued June 27, 2006. Accordingly, each relied-upon publication/patent qualifies as prior art at least under 35 U.S.C. § 102(a)(1), subject to any properly established earlier effective filing date for a particular claim.
Claims 1-6 and 9-14 are rejected under 35 U.S.C. § 103 as being unpatentable over Farinholt et al., in view of Troupe, and further in view of Johnson et al.
Claim 1
Farinholt expressly teaches a QKD receiver communicating with a transmitter that produces a plurality of quantum particles and teaches receiving and measuring those particles using a weak-measurement apparatus.
Farinholt states in its Abstract: “A quantum key distribution (QKD) receiver is provided for communicating with a transmitter that produces a plurality of entangled photon qubit pairs to send one qubit from each pair randomly alternating between basis states. The receiver includes a first polarized beam splitter, an orthogonal pair of photon detectors, a weak measurement apparatus, a broadcaster, an error rate estimator, and a post-processor. The first splitter receives the one qubit for passage or reflection. The photon detector pair measures the one qubit from passage or reflection. The apparatus performs a weak measurement on the one qubit and includes an impedance device to induce time delay, a pair of mirrors flanking the impedance device, and second and third polarized beam splitters for alternatively passing the one qubit to each other and to the pair of mirrors. The broadcaster for sending weak measurement results from the detectors to the transmitter. The error rate estimator determines whether the weak measurement satisfies a bit error threshold. The post-processor corrects the weak measurement from one of the basis states in response to a shared random key from the transmitter.” [Farinholt, Abstract; see also p. 18, claim 1.]
This disclosure teaches receiving quantum particles transmitted as a plurality through the quantum channel. The claimed “receiving a subset of quantum particles of a plurality of quantum particles transmitted on the quantum interconnect link” is satisfied because the receiver receives the members of the transmitted plurality that are subsequently selected for security-parameter evaluation.
Troupe makes the subset operation express: in operation (7), Alice and Bob separate their records into data associated with qubits prepared and measured in the same basis and data associated with qubits prepared and measured in different bases; operations (8)-(13) then use the different-basis subset for the weak-measurement security analysis. Thus, the cited art expressly identifies and analyzes a subset drawn from the transmitted/received photon plurality. [Troupe, col. 11, ll. 1-45.]
“This disclosure presents exemplary prepare and measure quantum key distribution protocols that decouple the necessary quantum channel error estimation from its dependency on sifting, or otherwise post-selecting, the detection outcomes. Rather than estimating Eve's coupling to the quantum channel from the statistics of the sifted key, this information is inferred from weak measurements made equally on all of the received photons immediately prior to post-selection by the photon detectors. This disclosure demonstrates that the accuracy of the weak measurement parameter estimation is robust to reasonable device imperfections, even in an adversarial environment, and hence the asymptotic security of this protocol can be inferred from the security analysis of BB84.” [Farinholt, p. 2, ¶ [0023].]
For the claimed transmitted physical condition comprising selected observables imparted within a first quantum degree of freedom, Farinholt expressly encodes the raw key in photon polarization and expressly identifies the linear/diagonal polarization bases. It then uses the temporal wavefunction as a second, weak-measurement pointer degree of freedom.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142]; FIG. 11.]
For the claimed coupling between the first and second quantum degrees of freedom, including indirectly imparting a coupled observable by imparting the selected observable, Farinholt further teaches the physical weak interaction between photon polarization/path and the temporal pointer:
“To implement the necessary weak measurement interaction, Bob 120 uses a polarizing interferometer consisting of two polarizing beam splitters oriented with the linear basis and a polarization independent optical delay 1190 in one path of the interferometer with duration δT << τ as in view 1100. Because the optical delay is small compared with the photon's temporal uncertainty, the entanglement between the photon's polarization and path is very weak. Just before each photon enters the polarizing interferometer, Bob uniformly randomly chooses to measure one of the two projectors onto H+ and H− by rotating the incoming photon's polarization state. On exiting the interferometer, the polarization of each photon then rotates back to its original state. By implementing the weak measurement interaction in this manner, the interaction strength is ensured to always be the same for both projectors as the same delay is used. The weak measurement pointer used here is the time degree of freedom for the photons' exiting of the source aperture. As long as the signal pulse's temporal wavefunction is well controlled and the detectors' timing jitter are relatively small compared to the weak measurement's optical delay, accurate estimates of delay time, and thus the weak measurement results, can be obtained.” [Farinholt, ¶ [0143]; FIG. 11.]
The same reference expressly confirms that the identity of the first and second degrees of freedom may be exchanged, and that an auxiliary degree of freedom can serve as the weak-measurement pointer:
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144].]
The coupling limitation is independently and even more directly stated by Troupe, which teaches coupling “another observable” of the same photon to the observable used to encode the key and using the auxiliary observable as the weak-measurement pointer:
“Implementation of the necessary weak measurements can be accomplished by weakly coupling another observable of each photon to the particular observable used to encode the key in the BB84 protocol. For example, for phase encoded implementations, the photon's polarization can be used as a pointer for the weak measurement, and vice versa for a polarization encoded protocol. From these pairs of weak measurement results, both the real and imaginary components of the weak values could be used to detect an eavesdropper. This weak measurement strategy could also be used to generalize the qubit protocols to higher-dimensional qudit two basis and complete MUB QKD protocols. A complete MUB qudit protocol could be especially interesting due to the very large (as compared to qubits) amount of channel information extracted per physical signal received, and the increased sensitivity of that channel information to an eavesdropper's intervention.” [Troupe, col. 22, ll. 29-62.]
Accordingly, the combined teachings map the claimed first set of quantum degrees of freedom to the degree of freedom carrying the encoded/selected observable (e.g., polarization or phase) and map the claimed second set to the auxiliary weak-measurement pointer degree of freedom (e.g., time or polarization). The weak coupling makes the pointer observable depend on, and thus indirectly reflect, the selected observable without the strong projective disturbance that would otherwise occur.
For determining the received physical condition and detecting a difference from the transmitted/expected condition, Troupe expressly teaches comparing received weak-measurement statistics to the weak values expected from Alice’s prepared/transmitted states.
“The central difference between the proposed protocol and BB84 (and its variants) is that the detection of Eve's presence does not rely on the estimated QBER of the sifted key. Alice and Bob independently probe the behavior of the quantum channel by means of weak measurements of particular observables, conditional on the results of the outcomes of Bob's measurements and the states prepared by Alice when the two bases disagree. Thus, the protocol uses the outcome results when Alice's and Bob's choices of basis disagree regarding the detection of Eve. This detection strategy is strictly more powerful than the sifted key QBER because any form of measurement by Eve must necessarily disturb either the incoming state from Alice or the time-reversed state back-propagated from Bob's measurement outcome.” [Troupe, cols. 9-10.]
“(7) Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, col. 11, ll. 1-45, protocol operations (7)-(13).]
These operations teach both sides of the comparison required by claim 1: (i) received pointer/weak-measurement observables measured by Bob and Alice, and (ii) expected/transmitted-state information derived from the transmitted raw-key/basis information and local transformations. The protocol expressly performs a comparison of the measured conditional averages to the values expected for the known transmitted/pre-selected state and uses a failure of that comparison as the security condition.
For “accessing data reflecting the transmitted physical condition,” Troupe expressly provides the separate classical disclosure of the preparation information and measurement information used to construct the expected condition:
“One can assume, as is usually the case, that Alice and Bob have access to a properly authenticated classical channel that Eve will be able to passively monitor. One can further assume that both Alice and Bob each locally have devices that produce the multiple, independent, and sufficiently random strings of binary numbers needed for the protocol.” [Troupe, col. 6, ll. 39-45.]
“Alice and Bob communicate over an authenticated classical channel 140 (without effective security from interception) and a quantum channel 150. A bit message over the classical channel 140 from Alice can be intercepted by Eve and reproduced to be forwarded to Bob. Eve also has access to the quantum channel 150. However for conventional protocols, a qubit message over the quantum channel 150 cannot be so readily intercepted without revealing the intrusion.” [Troupe, col. 12, ll. 1-8; FIG. 1.]
More specifically, Troupe’s broadcast preparation data identifies the information needed to reconstruct the transmitted/expected physical condition. Alice’s list P reveals the encoding-basis choice and list R supplies the encoded raw-key value for the selected subset; Bob’s list M and local-unitary information V identify the measurement basis/unitary used to select the weak observable. Farinholt’s disclosed hardware configuration then fixes the physical relationship between the encoded observable and the auxiliary pointer observable for example, polarization encoding with the temporal degree of freedom as the pointer, or phase encoding with polarization as the pointer. Accordingly, the accessed classical metadata, together with the known configured coupling, reflects the imparted selected observable and supplies the indication of the associated coupled/pointer observable required to establish the expected transmitted physical condition. [Troupe, col. 11, ll. 1-45; Farinholt, ¶¶ [0142]-[0144]; FIG. 11.]
Thus, the basis/raw-key information transmitted over the authenticated classical channel is data reflecting the transmitted physical condition rather than the quantum carrier itself: it identifies the preparation basis/state, while the configured weak-measurement coupling identifies the associated auxiliary pointer observable and its expected behavior. The receiver uses those data to evaluate whether the measured received physical condition is consistent with, or differs from, the expected condition corresponding to the transmitted state.
Finally, for the claimed notification of interference, Troupe teaches announcing whether the weak-measurement statistics pass the security test and aborting when the comparison is unsatisfactory. Johnson independently and expressly teaches an alarm notification when a quantum probe detects an intrusion:
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10; FIG. 5c.]
The alarm of Johnson is a direct implementation of the claimed “notification of interference”: it is generated in response to a significant change in the quantum probe signal and expressly notifies the end user of the intrusion. The Farinholt/Troupe comparison supplies the particular weak-measurement auxiliary-degree-of-freedom detection technique, and Johnson supplies the conventional downstream notification response.
One of ordinary skill in the art would have been motivated to combine Farinholt with Troupe because the references address the same narrow technical problem detecting and characterizing eavesdropping on a QKD quantum channel using weak measurements and employ the same Alice/Bob/Eve security model. Farinholt provides a concrete receiver implementation in which key information is encoded in one quantum degree of freedom and another degree of freedom functions as a weak-measurement pointer. Troupe provides the complementary protocol detail explaining how expected transmitted-state information is exchanged over the authenticated classical channel and how the measured weak values are compared against the values expected from the transmitted/pre-selected state. Using Troupe’s state-information exchange and conditional-comparison procedure with Farinholt’s concrete pointer implementation would have allowed the Farinholt receiver to determine whether a received auxiliary observable remains consistent with the observable expected from the transmitted state, which is precisely the security purpose shared by both references.
A person of ordinary skill also would have been motivated to add Johnson’s alarm/notification response because Farinholt and Troupe already produce a security-test result indicating whether the measured channel behavior is consistent with the expected transmitted behavior. Johnson is in the same QKD/eavesdropping field and teaches the ordinary system response to such a detected discrepancy: trigger an alarm that notifies the user and optionally take protective action. Adding that notification does not alter the weak-measurement physics or the QKD protocol; it merely communicates the detected security state to the user according to its established function. The resulting combination therefore represents the predictable use of known QKD weak-measurement, authenticated-state-information exchange, comparison, and alarm elements for their established functions, with a reasonable expectation of success and without any teaching away.
Accordingly, the combined teachings of Farinholt, Troupe, and Johnson teach or render obvious every limitation of claim 1, and claim 1 would have been obvious before the effective filing date of the claimed invention.
Claim 2
With respect to claim 2, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 2 additionally requires that a value representing one or more qudits be encoded by imparting the selected observables to the subset of quantum particles.
However, within analogous art, Troupe expressly teaches the missing higher-dimensional qudit implementation in the same weak-measurement QKD architecture:
“Implementation of the necessary weak measurements can be accomplished by weakly coupling another observable of each photon to the particular observable used to encode the key in the BB84 protocol. For example, for phase encoded implementations, the photon's polarization can be used as a pointer for the weak measurement, and vice versa for a polarization encoded protocol. From these pairs of weak measurement results, both the real and imaginary components of the weak values could be used to detect an eavesdropper. This weak measurement strategy could also be used to generalize the qubit protocols to higher-dimensional qudit two basis and complete MUB QKD protocols. A complete MUB qudit protocol could be especially interesting due to the very large (as compared to qubits) amount of channel information extracted per physical signal received, and the increased sensitivity of that channel information to an eavesdropper's intervention.” [Troupe, col. 22, ll. 29-62.]
This is not merely a generic mention of qudits. Troupe expressly teaches that the same weak-measurement strategy used for its qubit QKD protocol can be generalized to higher-dimensional qudit protocols, and it explains why the generalization is technically useful: a qudit can carry a larger amount of channel information per physical signal and can provide increased sensitivity of channel information to an eavesdropper’s intervention. Thus, Troupe teaches encoding higher-dimensional quantum information in the physical signal and applying the same weak-measurement disturbance-monitoring technique.
One of ordinary skill in the art would have been motivated to use Troupe’s expressly proposed qudit generalization in the Farinholt/Troupe system because both references already teach that the security parameter is derived from observables of quantum states and because Troupe identifies qudits as a direct extension of the disclosed protocol rather than a different operating principle. The skilled artisan would have expected the selected physical observable to encode a state in a higher-dimensional Hilbert space while the auxiliary weak-measurement pointer continued to monitor disturbance. This substitution would preserve the same transmit/measure/compare security mechanism while increasing the dimensionality of the encoded information.
Therefore, claim 2 would have been obvious.
Claim 3
With respect to claim 3, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 3 additionally requires identifying a second set of one or more quantum degrees of freedom and determining one or more coupled observables for each degree of freedom in that second set.
However, within analogous art, Farinholt expressly identifies the auxiliary degree of freedom and the observable used as the pointer. Its implementation states:
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142].]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144].]
The reference necessarily distinguishes the encoded degree of freedom from the auxiliary pointer degree of freedom: in one embodiment polarization is the encoded degree of freedom and time is the pointer; in another embodiment phase is encoded and polarization is the pointer. It further specifies what is measured in that second degree of freedom—time of detection or photon polarization—thereby teaching the claimed identification of the second degree of freedom and determination of its coupled observable.
One of ordinary skill would have been motivated to identify the auxiliary degree of freedom and corresponding coupled observable as part of configuring the weak-measurement apparatus because Farinholt expressly teaches multiple interchangeable implementations. The receiver cannot set the interferometer, delay, clock measurement, polarization optics, or expected weak value unless the apparatus knows which physical degree of freedom is functioning as the pointer and which observable is being read. Making that identification explicit is therefore an ordinary and necessary configuration operation for implementing the reference’s disclosed alternatives and yields the predictable result of selecting the correct probe observable. Claim 3 would have been obvious.
Claim 4
With respect to claim 4, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 4 additionally requires that the quantum degrees of freedom include one or more of polarization, time-of-arrival, spatial displacement, relative phase, orbital angular momentum, spatial modes, energy/frequency, quantized quadrature’s and/or spin. Because the claim uses the open alternative “one or more of,” a teaching of any one listed species satisfies this limitation; the cited art expressly teaches several of them.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142] (polarization and temporal/time-of-arrival pointer).]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144] (phase and polarization).]
Troupe also describes the pointer/encoding relationship in terms of photon polarization and phase and discusses spin observables used in the protocol. The cited disclosures therefore expressly teach at least polarization, time, and relative phase from the list recited in claim 4.
One of ordinary skill in the art would have been motivated to select among these expressly disclosed degrees of freedom according to the encoding convention and available optical hardware. Farinholt explicitly states that its particular implementation is only one of many possibilities and gives the phase/polarization reciprocal implementation as a concrete alternative. Selecting one of the expressly disclosed pointer/encoding degree-of-freedom pairs would have been a routine implementation choice with the predictable result of allowing the same weak-measurement security test to operate with the selected optical encoding. Claim 4 would have been obvious.
Claim 5
With respect to claim 5, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 5 additionally requires that the transmitted physical condition be received on a secondary communication channel separate from the quantum interconnect link.
“One can assume, as is usually the case, that Alice and Bob have access to a properly authenticated classical channel that Eve will be able to passively monitor. One can further assume that both Alice and Bob each locally have devices that produce the multiple, independent, and sufficiently random strings of binary numbers needed for the protocol.” [Troupe, col. 6, ll. 39-45.]
“Alice and Bob communicate over an authenticated classical channel 140 (without effective security from interception) and a quantum channel 150. A bit message over the classical channel 140 from Alice can be intercepted by Eve and reproduced to be forwarded to Bob. Eve also has access to the quantum channel 150. However, for conventional protocols, a qubit message over the quantum channel 150 cannot be so readily intercepted without revealing the intrusion.” [Troupe, col. 12, ll. 1-8; FIG. 1.]
“(7) Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, cols. 11-12, operations (7)-(13).]
Troupe expressly provides two physically/logically different communication paths: an authenticated classical channel 140 for broadcasting preparation/measurement information and a quantum channel 150 for the photon/qubit transmission. Alice broadcasts her encoding basis and key-related information on the classical channel, and Bob broadcasts measurement information. That classical information is the transmitted-state data used by the receiving side to determine the weak value/statistics that should be observed for the transmitted quantum condition.
Johnson independently reinforces the conventional use of separate data/probe channels in quantum-security systems.
“A method for providing eavesdropping detection of an optic fiber communication between two users includes the steps of exchanging both data and probe signals through at least two channels (400, 500) between the users, exchanging probe signals (143) on one channel (500 or 400) between quantum probe signal terminals, extracting a key for authentication from the probe signals, and exchanging data signals (142) between transmission units on another channel (400 or 500). A first portion of the key generated by the quantum probe signal terminals is used to authenticate the terminals, wherein a second portion of the key is dedicated to define commutation occurrences of commutation devices adapted to commutate the use of the channels (400, 500) for data (142) and probe (143) signals, thus detecting an eavesdropping event (300) which triggers an alarm (750). A further portion of the key can be used to encrypt the messages.” [Johnson, Abstract.]
A person of ordinary skill would have been motivated to use the separate authenticated classical channel taught by Troupe because quantum key distribution conventionally requires public exchange of basis and measurement information after or alongside quantum transmission. Keeping the transmitted-state metadata on a secondary classical channel allows the receiver to access the information needed for comparison without converting or disturbing the quantum carrier itself. The arrangement also matches the explicit two-channel architecture in Troupe and the separate probe/data channel practice confirmed by Johnson. The result is predictable and preserves the established function of each channel. Claim 5 would have been obvious.
Claim 6
With respect to claim 6, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 6 additionally requires that the notification of interference indicate detection of an eavesdropper accessing the quantum interconnect link.
“Because the weak value of a quantum system is equally defined by both the initial and final state of an individual system, the weak value is a useful attribute to use for detecting the presence of Eve. Access to a system's weak value is provided statistically by the mean value of sufficiently weak measurements that have been conditioned on particular initial and final states. Any interaction between Eve and the qubit transmitted between Alice and Bob will necessarily have an effect on the correlations between the initial and final states due to state disturbance and change the observed weak measurement statistics. Of particular interest for detecting an FS-attack, such disturbances are present and observable even in the cases when Alice and Bob measure in different bases. This enables them to monitor for the presence of Eve using the half of the signals that are usually discarded at the beginning of the protocol.” [Troupe, col. 6, ll. 8-25.]
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10.]
Troupe expressly characterizes the detected disturbance as evidence of Eve, the eavesdropper, and Johnson expressly states that the quantum-probe discrepancy signals an eavesdropping attempt and triggers an alarm notifying the end user of the intrusion. The claimed indication is therefore directly taught, not inferred from a generic fault alarm.
One of ordinary skill in the art would have been motivated to label the security-test failure as an eavesdropper notification because the purpose of the weak-measurement comparison in Farinholt and Troupe is expressly to detect Eve’s intervention. Johnson shows the conventional communication of that detection to a user as an intrusion alarm. Expressly identifying the cause of the alarm as eavesdropping gives the operator actionable security information and does not modify the underlying detection mechanism. Claim 6 would have been obvious.
Claim 9
Claim 9 recites the apparatus counterpart of the claim-1 method. The combination teaches the claimed probe, communication circuitry, processing circuitry, weak-measurement coupling, transmitted-state access, comparison, and notification limitations.
Farinholt expressly claims a physical QKD receiver that includes the probe/weak-measurement hardware, detectors, a broadcaster, an error-rate estimator, and a post-processor:
“A quantum key distribution (QKD) receiver for communicating with a transmitter that produces a plurality of entangled photon qubit pairs to send one qubit from each pair randomly alternating between basis states, said receiver comprising: a first polarized beam splitter for receiving the one qubit for passage or reflection; an orthogonal pair of photon detectors for measuring the one qubit from said passage or said reflection; an apparatus for performing a weak measurement on the one qubit, including an impedance device to induce time delay, a pair of mirrors flanking said impedance device, second and third polarized beam splitters for alternatively passing the one qubit to each other and to said pair of mirrors, and a pair of lenses flanking said second and third splitters to rotate the one qubit; a broadcaster for sending weak measurement results from said detectors to the transmitter; an error rate estimator to determine whether said weak measurement satisfies a bit error threshold; and a post-processor to correct said weak measurement from one of the basis states in response to a shared random key from the transmitter.” [Farinholt, p. 18, claim 1.]
The claimed “probe coupled with the quantum interconnect link” reads directly on Farinholt’s weak-measurement apparatus positioned in the incoming photon path. The apparatus receives an incoming qubit, performs a weak measurement, and uses a delay/interferometer arrangement that produces a pointer response in an auxiliary degree of freedom. The orthogonal detector pair and clock/delay apparatus are measurement structures for obtaining the received observable.
“To implement the necessary weak measurement interaction, Bob 120 uses a polarizing interferometer consisting of two polarizing beam splitters oriented with the linear basis and a polarization independent optical delay 1190 in one path of the interferometer with duration δT << τ as in view 1100. Because the optical delay is small compared with the photon's temporal uncertainty, the entanglement between the photon's polarization and path is very weak. Just before each photon enters the polarizing interferometer, Bob uniformly randomly chooses to measure one of the two projectors onto H+ and H− by rotating the incoming photon's polarization state. On exiting the interferometer, the polarization of each photon then rotates back to its original state. By implementing the weak measurement interaction in this manner, the interaction strength is ensured to always be the same for both projectors as the same delay is used. The weak measurement pointer used here is the time degree of freedom for the photons' exiting of the source aperture. As long as the signal pulse's temporal wavefunction is well controlled and the detectors' timing jitter are relatively small compared to the weak measurement's optical delay, accurate estimates of delay time, and thus the weak measurement results, can be obtained.” [Farinholt, ¶ [0143]; FIG. 11.]
Troupe supplies the communication and processing operation associated with the transmitted condition. It teaches an authenticated classical channel and the explicit broadcast/calculate/compare sequence:
“…Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, col. 11, ll. 1-45.]
The broadcaster/communication channel teaches the claimed communication circuitry configured to access transmitted physical-condition data. In Troupe, the P/R preparation information identifies the transmitted selected basis/state, while the M/V measurement-basis/unitary information determines the corresponding weak-measurement observable and expected weak value. Those accessed data therefore provide both the selected-observable information and an indication of the coupled/pointer observable required by claim 9. The error-rate estimator, post-processor, and computing implementation of Farinholt, together with Troupe’s calculation of conditional averages and comparison against expected weak values, teach processing circuitry configured to determine the received condition and compare it to the transmitted/expected condition.
“In accordance with a presently preferred embodiment of the present invention, the components, process steps, and/or data structures may be implemented using various types of operating systems, computing platforms, computer programs, and/or general purpose machines. In addition, artisans of ordinary skill will readily recognize that devices of a less general purpose nature, such as hardwired devices, may also be used without departing from the scope and spirit of the inventive concepts disclosed herewith. General purpose machines include devices that execute instruction code. A hardwired device may constitute an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), digital signal processor (DSP) or other related component.” [Farinholt, ¶ [0022].]
Johnson expressly teaches the resulting notification circuitry/function when the measured quantum probe indicates intrusion:
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10.]
One of ordinary skill would have been motivated to embody the Farinholt/Troupe operations in the disclosed receiver hardware because Farinholt already presents those functions as a receiver containing detector, weak-measurement, broadcaster, estimator, post-processing and executable-control elements. Troupe supplies the particular state-information exchange and comparison routine, while Johnson supplies the conventional alarm output. Combining these known hardware and processing functions would have produced no change in principle: the weak-measurement apparatus probes the auxiliary degree of freedom, the processing circuitry evaluates the measured pointer against the expected transmitted state, and the communication circuitry reports the result. Each component performs its established function and the resulting apparatus would have been predictable. Claim 9 would have been obvious.
Claim 10
With respect to claim 10, all limitations of claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 10 additionally requires a value representing one or more qudits to be encoded by imparting the selected observables to the subset of quantum particles.
“Implementation of the necessary weak measurements can be accomplished by weakly coupling another observable of each photon to the particular observable used to encode the key in the BB84 protocol. For example, for phase encoded implementations, the photon's polarization can be used as a pointer for the weak measurement, and vice versa for a polarization encoded protocol. From these pairs of weak measurement results, both the real and imaginary components of the weak values could be used to detect an eavesdropper. This weak measurement strategy could also be used to generalize the qubit protocols to higher-dimensional qudit two basis and complete MUB QKD protocols. A complete MUB qudit protocol could be especially interesting due to the very large (as compared to qubits) amount of channel information extracted per physical signal received, and the increased sensitivity of that channel information to an eavesdropper's intervention.” [Troupe, col. 22, ll. 29-62.]
For the same technical reasons discussed for claim 2, Troupe expressly proposes using the same weak-measurement strategy with higher-dimensional qudits. Implementing that stated qudit extension in Farinholt’s receiver would require only adapting the state preparation/measurement basis and the expected observable values while retaining the weak pointer, broadcaster, error estimator, and processing architecture. The expected benefits—greater channel information per signal and increased sensitivity to eavesdropping—are stated by Troupe itself. Claim 10 would have been obvious.
Claim 11
With respect to claim 11, all limitations of claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 11 additionally requires identifying a second set of one or more quantum degrees of freedom and determining one or more coupled observables for each of the second set.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142].]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144].]
These passages expressly identify the auxiliary degree of freedom—time in one implementation and polarization in another—and identify the measured pointer observable in that degree of freedom. A receiver implementing Farinholt’s disclosed alternatives must determine which pointer degree and observable are configured so that the processing circuitry can interpret the measured pointer correctly. That configuration step is an ordinary and predictable part of operating the disclosed probe. Claim 11 would have been obvious.
Claim 12
With respect to claim 12, all limitations of claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 12 additionally recites the same alternative list of quantum degrees of freedom as claim 4.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142] (polarization and temporal/time-of-arrival).]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144] (phase and polarization).]
Because claim 12 requires only “one or more of” the listed degrees of freedom, the express teachings of polarization, time/temporal position, and phase are sufficient to meet the limitation. Selecting among those expressly disclosed optical degrees of freedom according to encoding format and available detector/interferometer hardware would have been a routine design choice producing the expected pointer behavior.
Claim 12 would have been obvious.
Claim 13
With respect to claim 13, all limitations of claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 13 additionally requires that the transmitted physical condition be accessed on a secondary communication channel separate from the quantum interconnect link.
“Alice and Bob communicate over an authenticated classical channel 140 (without effective security from interception) and a quantum channel 150. A bit message over the classical channel 140 from Alice can be intercepted by Eve and reproduced to be forwarded to Bob. Eve also has access to the quantum channel 150. However, for conventional protocols, a qubit message over the quantum channel 150 cannot be so readily intercepted without revealing the intrusion.” [Troupe, col. 12, ll. 1-8; FIG. 1.]
“(7) Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, col. 11, ll. 1-45.]
The reference’s authenticated classical channel 140 is the claimed secondary communication channel, while quantum channel 150 is the quantum interconnect link. The basis/key and measurement information broadcast on channel 140 is exactly the information the processing logic uses to determine the expected transmitted condition and compare it to the received weak-measurement result. Implementing the communication circuitry of claim 9 to receive this information over the expressly taught classical channel would have been a direct, predictable implementation of Troupe’s protocol. Claim 13 would have been obvious.
Claim 14
With respect to claim 14, all limitations of claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 14 additionally requires that the interference notification indicate detection of an eavesdropper accessing the quantum interconnect link.
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10; FIG. 5c.]
Johnson’s alarm is generated because the quantum probe changes in a manner signaling an eavesdropping attempt, and it expressly notifies the end user of the intrusion. Incorporating that output into Farinholt’s receiver/processing architecture gives the apparatus an explicit eavesdropper indication responsive to the comparison result, with no change to the measurement process. A skilled artisan would have done so to communicate the security status detected by the receiver. Claim 14 would have been obvious.
Claims 7, 15, and 16-22 are rejected under 35 U.S.C. § 103 as being unpatentable over Farinholt et al., in view of Troupe, and further in view of Johnson et al., and further in view of Flament et al. (WO 2022/086634 A2).
Claim 7
With respect to claim 7, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 7 additionally requires that, upon detecting the difference, data reflecting the detected difference be transmitted to the transmitting device to cause adjustment of one or more transmission parameters to compensate for anomalies in the quantum interconnect link.
Flament is directed to real-time correction of quantum communication channels and expressly teaches determining a difference between an initial/transmitted polarization and a measured/received polarization, deriving a feedback parameter from that difference, and adjusting the optical transmission path for later quantum photons:
“Some embodiments provide for a system. The system comprises a polarization modulator optically coupled to a photon source by an optical fiber and at least one controller coupled to the polarization modulator. The at least one controller is configured to: determine, using a machine learning model and/or a lookup table, a feedback parameter based on one or more measurements of a polarization of probe photons at a location along the optical fiber, the probe photons being generated by the photon source; and using the feedback parameter, change a setting of the polarization modulator to change a polarization of quantum data photons propagating in the optical fiber subsequent to the probe photons.” [Flament, p. 1, Summary.]
“In some embodiments, the at least one controller is further configured to: determine a difference between an initial polarization of the probe photons as produced by the photon source and a final polarization of the probe photons as measured at an output of the polarization modulator, and wherein, determining the feedback parameter based on one or more measurements of the polarization of the probe photons comprises determining the feedback parameter based on the difference between the initial polarization and the final polarization.” [Flament, pp. 2-3, Summary.]
Flament further teaches the receive-side/remote-to-source control signaling required by claim 7:
“In some embodiments, microcontroller units 410a and 410b may be communicatively coupled to one another (e.g., via a network) in order to facilitate synchronization of the polarization compensation process. For example, microcontroller unit 410b may transmit trigger information (e.g., that the polarization has drifted beyond a threshold value) to microcontroller unit 410a. Microcontroller unit 410a may then transmit instructions to probe photon source 102 and/or polarization modulator 105 to begin transmitting probe photons with a known, encoded polarization state to begin the polarization compensation process by adjusting a setting of polarization modulator 112 using a feedback parameter generated by polarization correction facility 122.” [Flament, p. 23, ll. 1-11; FIGS. 4-6.]
“A method for correcting a polarization of photons transmitted through an optical fiber, the method comprising: transmitting a sequence of photons including data photons and one or more probe photons through an optical fiber; measuring a polarization of the one or more probe photons after traversing the optical fiber; determining a difference between an initial polarization of the one or more probe photons and the measured polarization of the one or more probe photons; determining, using a machine learning model and/or lookup table, a feedback parameter based on the difference between the initial polarization and the measured polarization; and changing, using the feedback parameter, a parameter of a polarization modulator coupled to the optical fiber to correct a polarization of the data photons.” [Flament, p. 43, claim 39; see also FIG. 6, steps 602-606.]
The trigger information identifying that polarization has drifted beyond a threshold is data reflecting the detected difference. It is transmitted from microcontroller 410b to microcontroller 410a, which then causes the source/polarization-modulator side to alter operation. The feedback parameter is expressly derived from the difference between the initial and measured polarization and is used to change the modulator so that later quantum data photons are corrected. Thus, Flament teaches the complete feedback loop recited in claim 7.
One of ordinary skill in the art would have been motivated to combine Flament’s feedback correction with the Farinholt/Troupe/Johnson detection system because the references address complementary aspects of the same quantum optical channel problem. Farinholt and Troupe detect a deviation from expected quantum-state behavior by comparing measured weak-pointer observables with expected transmitted-state information; Flament uses a measured deviation between transmitted/initial and received polarization to generate feedback that compensates channel drift. In a practical QKD link, not every detected deviation is malicious; fiber birefringence, temperature, stress, source drift, and other channel anomalies can change measured observables. Once the Farinholt/Troupe receiver has quantified a discrepancy, using that discrepancy as input to the known Flament feedback loop would predictably permit correction of benign channel anomalies while leaving the security test available to identify eavesdropping.
The combination would not require changing Farinholt’s basic weak-measurement security principle. The receive-side subsystem would continue measuring the auxiliary observable and detecting a difference; the existing classical/control path would carry data reflecting that difference; and Flament’s controller/modulator would perform its established function of changing a transmission parameter for subsequent photons. Because Flament expressly uses the same type of quantum optical fiber channel and expressly communicates trigger information from the measurement side toward the photon-source/modulator side, a person of ordinary skill would have had a reasonable expectation of success. Claim 7 would have been obvious.
Claim 15
For purposes of prior-art examination only, and without withdrawing the above 35 U.S.C. § 112(b) rejection, claim 15 is interpreted as requiring the apparatus of claim 9 to be configured to transmit data reflecting the detected difference to the transmitting device in a manner that causes the transmitting device to adjust one or more transmission parameters to compensate for anomalies in the quantum interconnect link.
With respect to claim 15, all limitations of apparatus claim 9 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 15 additionally requires the feedback-compensation capability recited in claim 7 in the apparatus-claim context under the construction stated above.
“In some embodiments, microcontroller units 410a and 410b may be communicatively coupled to one another (e.g., via a network) in order to facilitate synchronization of the polarization compensation process. For example, microcontroller unit 410b may transmit trigger information (e.g., that the polarization has drifted beyond a threshold value) to microcontroller unit 410a. Microcontroller unit 410a may then transmit instructions to probe photon source 102 and/or polarization modulator 105 to begin transmitting probe photons with a known, encoded polarization state to begin the polarization compensation process by adjusting a setting of polarization modulator 112 using a feedback parameter generated by polarization correction facility 122.” [Flament, p. 23, ll. 1-11.]
“Some embodiments provide for a system. The system comprises a polarization modulator optically coupled to a photon source by an optical fiber and at least one controller coupled to the polarization modulator. The at least one controller is configured to: determine, using a machine learning model and/or a lookup table, a feedback parameter based on one or more measurements of a polarization of probe photons at a location along the optical fiber, the probe photons being generated by the photon source; and using the feedback parameter, change a setting of the polarization modulator to change a polarization of quantum data photons propagating in the optical fiber subsequent to the probe photons.” [Flament, p. 1, Summary.]
Flament’s microcontrollers, polarization correction facility, and polarization modulator are direct apparatus counterparts to the claimed processing/communication path: measured difference data is communicated to the control side, a feedback parameter is determined, and the modulator is adjusted to compensate the channel. Incorporating those known controller/modulator elements into Farinholt’s QKD receiver apparatus would provide the exact claimed capability to cause a transmitting device to adjust one or more transmission parameters in response to the detected difference.
One of ordinary skill would have been motivated to make this apparatus combination for the same detailed reasons stated for claim 7: the weak-measurement receiver identifies a channel-state discrepancy, while Flament provides a known closed-loop quantum-fiber correction subsystem designed to act on such discrepancies. The controller and modulator retain their normal functions, and the expected result is correction of polarization/channel anomalies for subsequent quantum particles. Claim 15 would have been obvious.
Claim 16
For purposes of prior-art examination only, and without withdrawing the above 35 U.S.C. § 112(b) rejection, claim 16 is interpreted consistently with claim 1 and the specification such that (i) “interconnected observables” and “coupled observables” refer to the same auxiliary observables and (ii) “the second set of one or more subset of quantum particles” refers to the previously recited second set of one or more quantum degrees of freedom. Claims 17-22 are examined on the same limited construction because they depend from claim 16.
Claim 16 recites the computer-program-product implementation of the same quantum-link receiving, auxiliary-degree-of-freedom measurement, transmitted-state access, comparison, and interference-notification operations recited in claim 1.
Farinholt and Troupe teach the underlying operations, Johnson teaches the explicit intrusion notification, and Flament expressly teaches storing quantum-communication control instructions on a non-transitory computer-readable storage medium.
“In accordance with a presently preferred embodiment of the present invention, the components, process steps, and/or data structures may be implemented using various types of operating systems, computing platforms, computer programs, and/or general purpose machines. In addition, artisans of ordinary skill will readily recognize that devices of a less general purpose nature, such as hardwired devices, may also be used without departing from the scope and spirit of the inventive concepts disclosed herewith. General purpose machines include devices that execute instruction code. A hardwired device may constitute an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), digital signal processor (DSP) or other related component.” [Farinholt, ¶ [0022].]
Farinholt therefore expressly contemplates implementation of the disclosed process steps and data structures using computer programs and instruction-executing general-purpose machines. The particular quantum operations implemented by that program include the received-photon weak measurement and error/security estimation described above.
“This disclosure introduces exemplary methods to utilize single qubit preparation and measurement to perform secure quantum key distribution that explicitly removes the dependency of channel estimation on the detected bit values. Exemplary embodiments estimate the phase and bit errors of the channel by the use of weak measurements of particular observables performed immediately preceding Bob's final post-selections. This approach decouples the error analysis from Bob's detection outcomes, and therefore removes the assumption of fair sampling implicit in all other prepare and measure QKD protocols by using the weak measurement results from all received signals equally to perform security parameter estimation.” [Farinholt, ¶ [0071].]
“(7) Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, col. 11, ll. 1-45.]
Those programmatic operations correspond to receiving the quantum-particle measurements through the QKD receiver interface, determining the received physical condition from measured observables, accessing transmitted-state data, comparing the two conditions, and determining the security condition. Troupe’s P/R preparation data identify the transmitted selected basis/state, while the M/V basis/unitary data determine the weak observable and expected weak value used in the comparison; accordingly, the accessed data provide the recited selected-observable information and the indication of the coupled/pointer observable. The Farinholt implementation additionally provides the concrete coupled auxiliary degree of freedom:
“To implement the necessary weak measurement interaction, Bob 120 uses a polarizing interferometer consisting of two polarizing beam splitters oriented with the linear basis and a polarization independent optical delay 1190 in one path of the interferometer with duration δT << τ as in view 1100. Because the optical delay is small compared with the photon's temporal uncertainty, the entanglement between the photon's polarization and path is very weak. Just before each photon enters the polarizing interferometer, Bob uniformly randomly chooses to measure one of the two projectors onto H+ and H− by rotating the incoming photon's polarization state. On exiting the interferometer, the polarization of each photon then rotates back to its original state. By implementing the weak measurement interaction in this manner, the interaction strength is ensured to always be the same for both projectors as the same delay is used. The weak measurement pointer used here is the time degree of freedom for the photons' exiting of the source aperture. As long as the signal pulse's temporal wavefunction is well controlled and the detectors' timing jitter are relatively small compared to the weak measurement's optical delay, accurate estimates of delay time, and thus the weak measurement results, can be obtained.” [Farinholt, ¶ [0143].]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, p. 16, ¶ [0144].]
Flament expressly supplies the non-transitory computer-readable-storage-medium form recited by claim 16:
“Computer-executable instructions implementing the techniques described herein (when implemented as one or more functional facilities or in any other manner) may, in some embodiments, be encoded on one or more computer-readable media to provide functionality to the media. Computer-readable media include magnetic media such as a hard disk drive, optical media such as a Compact Disk (CD) or a Digital Versatile Disk (DVD), a persistent or non-persistent solid-state memory (e.g., Flash memory, Magnetic RAM, etc.), or any other suitable storage media. Such a computer-readable medium may be implemented in any suitable manner, including as computer-readable storage media 1206 of FIG. 12 described below (i.e., as a portion of a computing device 1200) or as a stand-alone, separate storage medium. As used herein, “computer-readable media” (also called “computer-readable storage media”) refers to tangible storage media. Tangible storage media are non-transitory and have at least one physical, structural component.” [Flament, p. 33, ll. 11-28; FIG. 12.]
Johnson supplies the explicit interference/eavesdropping notification output:
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10.]
One of ordinary skill in the art would have been motivated to implement the Farinholt/Troupe comparison procedure as stored program instructions because Farinholt expressly teaches computer-program/general-purpose-machine implementation, while the comparison, conditional averaging, threshold test, broadcast handling, and security-status decision are digital data-processing operations naturally executed by the receiver’s processor. Flament also in quantum optical communications expressly teaches that such control techniques may be encoded as computer-executable instructions on tangible, non-transitory computer-readable storage media. Storing the executable instructions in non-transitory memory would provide persistence, repeatable execution, and ordinary integration with the QKD receiver/controller hardware without altering the quantum-measurement functions.
The combination is therefore not a conversion of a purely physical phenomenon into software by hindsight; both Farinholt and Flament expressly contemplate programmable/computer implementation. The processor executes the known algorithms, while the optical weak-measurement apparatus performs the physical measurement. Each part retains its established function, and a skilled artisan would have reasonably expected the stored instructions to control the disclosed receiver and comparison sequence successfully. Claim 16 would have been obvious.
Claim 17
With respect to claim 17, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 17 additionally requires qudit encoding.
“Implementation of the necessary weak measurements can be accomplished by weakly coupling another observable of each photon to the particular observable used to encode the key in the BB84 protocol. For example, for phase encoded implementations, the photon's polarization can be used as a pointer for the weak measurement, and vice versa for a polarization encoded protocol. From these pairs of weak measurement results, both the real and imaginary components of the weak values could be used to detect an eavesdropper. This weak measurement strategy could also be used to generalize the qubit protocols to higher-dimensional qudit two basis and complete MUB QKD protocols. A complete MUB qudit protocol could be especially interesting due to the very large (as compared to qubits) amount of channel information extracted per physical signal received, and the increased sensitivity of that channel information to an eavesdropper's intervention.” [Troupe, col. 22, ll. 29-62.]
Troupe expressly teaches generalizing the same weak-measurement QKD protocol from qubits to higher-dimensional qudits. The program instructions of claim 16 would merely represent and process the higher-dimensional basis/state values instead of binary qubit values, while the physical encoding and weak-pointer measurement continue performing the same functions. Because Troupe identifies the qudit extension and its increased information/sensitivity benefit, implementing that extension in the computer-controlled QKD receiver would have been a predictable software/state-representation adaptation. Claim 17 would have been obvious.
Claim 18
With respect to claim 18, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 18 additionally requires identifying a second set of quantum degrees of freedom and determining interconnected observables for that set.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak
measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142].]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144].]
Farinholt explicitly identifies the auxiliary degree of freedom and its corresponding pointer observable in alternative implementations. Program instructions controlling the receiver must likewise identify the configured pointer degree and interpret its measured observable. Encoding those configuration choices in the stored program of claim 16 is the ordinary software implementation of the expressly taught hardware alternatives and would have been predictable. Claim 18 would have been obvious.
Claim 19
With respect to claim 19, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 19 additionally recites the same alternative quantum-degree-of-freedom list addressed above.
“Section VIII Implementation: To indicate the feasibility of the protocol we will now sketch one particular implementation. Let one suppose that the raw key information is encoded in the polarization of the signal photons with Alice 110 randomly choosing to encoded in either the linear polarization basis (Z) or the diagonal basis (X). Furthermore, the weak measurement pointer state will be the temporal wavefunction of the signal pulses. The weak measurement pointer states are prepared so that the single photons are emitted with a temporal envelope that is Gaussian shaped with a fixed width τ and a peak value that occurs at a known time as determined by an accurate clock at the source 1010. Bob 120 possesses the clock 1170 that is synchronized with Alice's source clock. Bob 120 uses this clock 1170 to record the time each photon is detected by the single photon detectors that perform the final Z basis measurement. In the new protocol, Bob 120 must also weakly measure one of the projectors onto the two H polarization states.” [Farinholt, ¶ [0142] (polarization and time).]
“Finally, one can observe that this implementation is only one of many possibilities. For example, in the case that the raw key information is encoded into the phase of the signal
pulses, the polarization degree of freedom could be used as the weak measurement pointer. Bob would then utilize weak coupling between the paths inside of the appropriate non-polarizing interferometer and the photons' polarization to implement a weak measurement of phase. Additionally, while one can chose to highlight using an additional degree of freedom of the photons themselves for the weak measurement pointer states, in principle these states could be the states of some other quantum systems prepared by Bob, who would weakly couple this system to each photon upon receipt and then strongly measure this system independently of the photons.” [Farinholt, ¶ [0144] (phase and polarization).]
The “one or more of” limitation is met by the express polarization, temporal/time-of-arrival, and phase implementations. Programming the control/processing system for one of these disclosed physical encodings and pointer choices would have been a routine configuration task. Claim 19 would have been obvious.
Claim 20
With respect to claim 20, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 20 additionally requires that the transmitted physical condition be received on a secondary communication channel separate from the quantum interconnect link.
“Alice and Bob communicate over an authenticated classical channel 140 (without effective security from interception) and a quantum channel 150. A bit message over the classical channel 140 from Alice can be intercepted by Eve and reproduced to be forwarded to Bob. Eve also has access to the quantum channel 150. However for conventional protocols, a qubit message over the quantum channel 150 cannot be so readily intercepted without revealing the intrusion.” [Troupe, col. 12, ll. 1-8; FIG. 1.]
“(7) Bob broadcasts the list M (revealing his detector basis choices), while simultaneously, Alice broadcasts her list P (revealing her encoding basis choices). Alice separates each of her lists R, P, α, and U into two distinct lists corresponding to data associated with qubits prepared and measured in the same basis, and those that were not. (8) Alice broadcasts the different basis key list R. (9) Bob calculates the average of his weak measurement results β for which Alice's and Bob's bases disagree conditional on the associated bit values in R that Alice used to encode the photons. Bob checks that these averages are close enough to those specified by the weak values of the observables measured with the particular pre-selected states determined by R and the local unitary transformations defined by V. (10) Bob announces to Alice whether or not the statistics of his weak measurements have passed the security tests. If they did not pass, Alice and Bob abort the protocol, otherwise they proceed. (11) Bob broadcasts the results of his measurements D for which the bases disagreed. (12) Alice calculates the average of her weak measurement results α conditional on the associated values for Bob's measurement outcomes D. If no Eve is present, these conditional averages will be consistent with the associated weak values of the weakly measured observables given by Bob's measurement outcomes and Alice's local unitary transformations defined by U. (13) If the conditional and marginal statistics of Alice's weak measurement results are close enough to those that are expected, Alice will announce that the channel is secure, otherwise Alice and Bob abort the protocol.” [Troupe, col. 11, ll. 1-45.]
Troupe’s authenticated classical channel is expressly separate from the quantum channel and carries the basis, key-list, and measurement data used by the processing routine to determine the expected transmitted state and conduct the comparison. Program instructions that receive and process those classical messages through a communication interface are the ordinary software implementation of Troupe’s disclosed protocol and would have been predictable. Claim 20 would have been obvious.
Claim 21
With respect to claim 21, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 21 additionally requires the notification to indicate detection of an eavesdropper accessing the quantum interconnect link.
“Because the weak value of a quantum system is equally defined by both the initial and final state of an individual system, the weak value is a useful attribute to use for detecting the presence of Eve. Access to a system's weak value is provided statistically by the mean value of sufficiently weak measurements that have been conditioned on particular initial and final states. Any interaction between Eve and the qubit transmitted between Alice and Bob will necessarily have an effect on the correlations between the initial and final states due to state disturbance and change the observed weak measurement statistics. Of particular interest for detecting an FS-attack, such disturbances are present and observable even in the cases when Alice and Bob measure in different bases. This enables them to monitor for the presence of Eve using the half of the signals that are usually discarded at the beginning of the protocol.” [Troupe, col. 6, ll. 8-25.]
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10.]
The stored program instructions would simply cause the system to output the security classification already produced by the weak-measurement comparison—namely that an intrusion/eavesdropping attempt has been detected. Johnson expressly implements exactly that result as an alarm notifying the end user. Adding the corresponding output instruction to the program would have been an ordinary, predictable implementation of the known detection result. Claim 21 would have been obvious.
Claim 22
For purposes of prior-art examination only, and without withdrawing the above 35 U.S.C. § 112(b) rejection, claim 22 is interpreted as requiring the program instructions of claim 16, when executed, to cause transmission of data reflecting the detected difference to the transmitting device so as to cause adjustment of one or more transmission parameters to compensate for anomalies in the quantum interconnect link.
With respect to claim 22, all limitations of claim 16 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 22 additionally requires
transmitting data reflecting the detected difference to the transmitting device so as to cause adjustment of one or more transmission parameters to compensate for anomalies.
“In some embodiments, microcontroller units 410a and 410b may be communicatively coupled to one another (e.g., via a network) in order to facilitate synchronization of the polarization compensation process. For example, microcontroller unit 410b may transmit trigger information (e.g., that the polarization has drifted beyond a threshold value) to microcontroller unit 410a. Microcontroller unit 410a may then transmit instructions to probe photon source 102 and/or polarization modulator 105 to begin transmitting probe photons with a known, encoded polarization state to begin the polarization compensation process by adjusting a setting of polarization modulator 112 using a feedback parameter generated by polarization correction facility 122.” [Flament, p. 23, ll. 1-11.]
“A method for correcting a polarization of photons transmitted through an optical fiber, the method comprising: transmitting a sequence of photons including data photons and one or more probe photons through an optical fiber; measuring a polarization of the one or more probe photons after traversing the optical fiber; determining a difference between an initial polarization of the one or more probe photons and the measured polarization of the one or more probe photons; determining, using a machine learning model and/or lookup table, a feedback parameter based on the difference between the initial polarization and the measured polarization; and changing, using the feedback parameter, a parameter of a polarization modulator coupled to the optical fiber to correct a polarization of the data photons.” [Flament, p. 43, claim 39; FIG. 6.]
Flament expressly teaches both the data communication and the corrective action: receive-side microcontroller 410b transmits trigger information reflecting excessive polarization drift to microcontroller 410a; that control side transmits instructions to the probe photon source and/or polarization modulator; and the feedback parameter derived from the measured difference changes the modulator to correct subsequent photons. The computer-executable instructions disclosed by Flament can implement those steps on the non-transitory medium already relied upon for claim 16.
One of ordinary skill would have been motivated to add this stored feedback routine because it is the programmable implementation of a known closed-loop quantum-fiber correction technique. The Farinholt/Troupe program already determines a discrepancy between expected/transmitted and received observables; Flament shows that such discrepancy information can be sent to the source/modulator control side and converted into a parameter adjustment. Combining the routines would predictably provide automatic compensation of benign channel anomalies while retaining the eavesdropping security test. Claim 22 would have been obvious.
Claim 8 is rejected under 35 U.S.C. § 103 as being unpatentable over Farinholt et al., in view of Troupe, and further in view of Johnson et al., and further in view of Elliott.
Claim 8
For purposes of prior-art examination only, and without withdrawing the above claim objection, the phrase “encoded valued” in claim 8 is interpreted as “encoded value,” consistent with the apparent intended wording identified in the claim objection.
With respect to claim 8, all limitations of claim 1 are taught by Farinholt, Troupe, and Johnson for the detailed reasons set forth above, except wherein claim 8 additionally requires, upon detecting the difference, remediating at least one irregularity on the quantum interconnect link to obscure an eavesdropper’s ability to identify an encoded value transmitted via the quantum interconnect link.
Johnson already teaches protective action after quantum-probe eavesdropper detection, including blocking transmission and rerouting traffic on non-eavesdropped channels:
“A significant change in Quantum probe signal value signals an eavesdropping attempt detection. If an intrusion is detected by probe terminal 740 an ALARM is triggered 750 which generates at least one of several actions: an alarm notifies the end-user of the intrusion, blocking of data signals transmission, traffic rerouting on non-eavesdropped channels.” [Johnson, col. 11, ll. 5-10.]
Johnson also expressly teaches a post-detection response that can directly interfere with the compromised information flow: “Alarm 750 can be connected with different further procedural steps of a reaction on the detected eavesdropping as redirecting the flow of information to a different channel and/or to change the content of the information to be transmitted on said channel.” [Johnson, col. 7, ll. 23-28; FIG. 2a.]
Elliott provides an even more specific QKD remediation teaching: after identifying eavesdropping using quantum cryptography, the system changes the path so subsequent transmissions use a different route.
“Systems and methods consistent with the present invention provide mechanisms for distributing encryption keys, using quantum cryptographic techniques, across multiple switches and links in a multi-node quantum key distribution network. Systems and methods consistent with the present invention further provide mechanisms for detecting eavesdropping on the quantum key distribution path and for routing the distribution of encryption keys around the eavesdropping in the network. Systems and methods consistent with the present invention may also discover the location of an eavesdropper at a QKD switch and/or link along the QKD path in the QKD network.” [Elliott, cols. 3-4.]
“A method of routing around eavesdroppers in a network, comprising: establishing a first path in the network; transmitting data symbols over the first path; identifying eavesdropping on the first path using quantum cryptography; establishing a second path in the network responsive to the eavesdropping identification, wherein the second path comprises a different route through the network than the first path; and transmitting data symbols over the second path.” [Elliott, col. 11, ll. 31-44, claims 16-17.]
Elliott’s establishment of a second, different route responsive to eavesdropping identification is a direct remediation of the irregularity/security compromise detected on the first path. Moving subsequent data/key distribution away from the compromised path reduces or eliminates the detected eavesdropper’s continuing access to the encoded information. Johnson independently teaches both rerouting and changing the content of information transmitted after eavesdropping is detected, which directly supports obscuring what the eavesdropper can identify after the irregularity is found. The cited remediation therefore addresses not merely notification, but protective modification of the information path/content in response to the detected compromise.
One of ordinary skill in the art would have been motivated to apply Elliott’s rerouting remediation to the Farinholt/Troupe/Johnson weak-measurement detector because the purpose of detecting eavesdropping is to preserve confidentiality after a compromise is identified. Farinholt and Troupe supply a sensitive way to detect the channel disturbance; Johnson supplies an alarm and teaches that traffic may be blocked or rerouted; Elliott, in a QKD network, expressly teaches creating a different path responsive to eavesdropping identification. Using that known remediation after the weak-measurement security test fails would predictably prevent the detected eavesdropper on the compromised route from continuing to observe the encoded values.
The proposed combination does not use the present application as a roadmap to invent a new remedy. Both Johnson and Elliott independently teach the same general post-detection action avoid the compromised channel/path within quantum-communication security systems. A skilled artisan would have recognized rerouting/teardown as a standard protective response once the detector identifies a compromised link, and would have had a reasonable expectation that subsequent quantum/key traffic on a different non-eavesdropped route would reduce the adversary’s access. Claim 8 would have been obvious.
Claims 1-22 are rejected under 35 U.S.C. § 103 for the reasons set forth above. Each rejection identifies the scope and content of the relied-upon prior art, the differences from the claimed subject matter, and an articulated reason with rational underpinning for the proposed combination, consistent with Graham, KSR, and MPEP §§ 2141 and 2143.
It is noted that any citations to specific pages, columns, lines, or figures in the prior art references and any interpretation of the reference should not be considered to be limiting in any way. A reference is relevant for all it contains and may be relied upon for all that it would have reasonably suggested to one having ordinary skill in the art. See MPEP § 2123.
Conclusion
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/MOHAMMED ABDELRAHEEM/Examiner, Art Unit 2635
/OMAR S ISMAIL/Primary Examiner, Art Unit 2635
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