DETAILED ACTION
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 .
Response to Arguments
Claim Rejections - 35 USC § 101
The prior 35 USC § 101 rejection of claims 1-12 has been withdrawn.
Claim Rejections - 35 USC § 103
Applicant's arguments, filed 01/07/2026, have been fully considered but they are not persuasive. Applicant correctly states that Ofek implements a cat-code QEC protocol in a superconducting photonic resonator system. The Examiner agrees that Ofek does not explicitly discuss spin systems or angular momentum operators.
However, Applicant's argument overlooks the conceptual generality and transferability of the QEC methodology disclosed by Ofek. Ofek does not merely present a collection of experimental steps; it demonstrates a novel, hardware-efficient QEC architecture (the cat-code) based on fundamental principles of symmetry, syndrome measurement, and feedback correction. The paper concludes by explicitly advocating for the adaptation of its QEC schemes to exploit "hardware platforms beyond the purview of traditional architectures" (NPL1, Page 4). This statement directly motivates a person of ordinary skill in the art (POSITA) to consider applying the cat-code QEC framework to other hardware platforms, such as spin systems.
While Ofek's physical implementation uses photon parity (â operators), the logical structure of its error correction is generic:
Error Categorization: It identifies the dominant error channel (photon loss/â) and characterizes its effect as a logical operation (a π/2 phase rotation).
Syndrome Extraction: It identifies a measurable symmetry (photon number parity) that is flipped by the error.
Correction: It uses the syndrome history to apply a counteracting unitary.
This logical framework is not limited to photonic systems. A POSITA seeking to protect quantum information in a spin system would recognize this framework as a powerful template.
Furthermore, Applicant argues that the combination fails to teach "categorizing products of angular momentum as phase errors and amplitude errors" and obtaining syndrome measurements for them.
The Examiner maintains that adapting Ofek's generic QEC methodology to the spin-cat platform taught by Davis would require the POSITA to perform this categorization as a matter of routine design choice. The analysis is as follows:
Ofek teaches the step of "categorizing Kraus operators." It does so by analyzing the system's dominant decoherence channel (photon loss) to understand its effect (NPL1, Pages 11-12, Eqs. 2-8).
Davis teaches that the relevant physical system is a collective spin J, and that interactions are governed by an angular momentum operator J_z (NPL2, Page 1, Eq. 1).
Therefore, a POSITA implementing Ofek's QEC framework on Davis's spin-cat platform would necessarily analyze the dominant decoherence channels of the spin system. For an ensemble spin system, common error channels (e.g., dephasing, collective relaxation, inhomogeneous broadening) are naturally described by operators that are functions of the collective angular momentum components J_x, J_y, J_z. Classifying these errors into types (e.g., "phase errors" from J_z-like operators and "amplitude errors" from J_x, J_y-like operators) is a standard practice in designing QEC codes for spin or qubit systems.
The claim language "products of angular momentum" describes a mathematical form for these error operators. Identifying this form is inherent to modeling errors in a spin system, just as Ofek identified the form (â) for errors in a resonator. The combination provides the motivation (to protect spin-cats using a proven QEC method) and the tools (the spin-cat itself and the QEC framework). The specific mathematical description of errors flows naturally from the chosen physical system.
The combination teaches all conceptual steps of the claim:
Ofek teaches performing QEC via a cat-code framework (error categorization, syndrome measurement, correction).
Davis teaches that the cat-state encoding can be physically realized in a collective spin system.
It would have been obvious to a POSITA, motivated by Ofek's successful results and its call to adapt the scheme to new hardware, to implement Ofek's QEC methodology to protect the valuable, but decoherence-prone, spin-cat states taught by Davis. The specific act of modeling the spin system's errors using angular momentum operators is a necessary and routine part of that implementation process, not a patentable advance.
Therefore, the rejection under 35 U.S.C. § 103 is maintained.
Claim Rejections - 35 USC § 103
In the event the determination of the status of the application as subject to AIA 35 U.S.C. 102 and 103 (or as subject to pre-AIA 35 U.S.C. 102 and 103) is incorrect, any correction of the statutory basis (i.e., changing from AIA to pre-AIA ) for the rejection will not be considered a new ground of rejection if the prior art relied upon, and the rationale supporting the rejection, would be the same under either status.
The following is a quotation of 35 U.S.C. 103 which forms the basis for all 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.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claim(s) 1-3, 5-8, and 10-12 are rejected under 35 U.S.C. 103 as being unpatentable over “Demonstrating Quantum Error Correction that Extends the Lifetime of Quantum Information” (hereinafter D1) and further in view of “Painting Nonclassical States of Spin or Motion with Single Photons” (hereinafter D2).
Claim 1: D1 teaches method for performing error correction in quantum computation in a spin system, the method comprising the steps of:
categorizing Kraus operators as polynomials in angular momentum that lead to phase errors and amplitude errors (e.g. the dominant error is analyzed as a Lindblad operator â - Page 11, Eq. 2-4);
obtaining syndrome measurements of the phase errors and the amplitude errors (e.g. photon loss causes a π/2 phase shift, monitored via parity - Page 2);
correcting the amplitude errors and the phase errors by constructing one or more quantum error-correcting codes (e.g. the cat code is implemented with real-time feedback - Page 3, "full QEC protocol"); and
encoding each logical qubit in a cat-state-based code with the one or more quantum error-correcting codes (e.g. the "cat code" - Pages 1, 6).
Not explicitly taught by D1 is encoding qubits in spin-cat states.
However, D2 directly and unequivocally supplies the missing element: the generation and manipulation of cat states in a collective atomic spin system. D2 teaches that a spin system is a suitable and desirable platform for creating macroscopic quantum superpositions (spin-cats) for applications in precision measurement and quantum information (Page 1).
Therefore, it would have been obvious to a person of ordinary skill in the art (POSITA), before the effective filing date of the claimed invention, to combine the teachings of D1 and D2 in order to implement robust QEC on promising spin-based quantum systems.
Claim 2: D1 and D2 teach the method of claim 1 further comprising the step of creating a universal set of gates including the step of developing a bias-preserving CNOT gate protocol suitable for errors in spin systems. For instance, D1 teaches a complete, hardware-efficient QEC system. And D2 teaches generating the fundamental encoding unit (spin-cat states) in a spin system. A POSITA seeking to build a functional quantum computer using this spin-cat QEC framework would be intrinsically motivated to create a universal set of gates to perform computations. The development of a bias-preserving CNOT gate protocol is a known design goal in the art for systems with biased noise (e.g., where phase errors dominate amplitude errors, a characteristic of the cat-code approach exemplified by D1). It would have been obvious to a POSITA to develop such a gate protocol suitable for the spin system of D2 in order to execute universal quantum computation on the error-corrected logical qubits.
Claim 3: D1 and D2 teach the method of claim 2 but fail to teach that the developing step further comprising the step of using a neutral atom architecture and entangling interaction associated with a Rydberg blockade to implement the bias-preserving CNOT gate. However, D2 teaches the use of a collective atomic spin system. The neutral atom architecture is a well-known and standard platform for implementing quantum logic with atomic spins. The Rydberg blockade mechanism is a conventional and widely known method for generating entangling interactions in neutral atom arrays. It would have been obvious to a POSITA to select this standard architecture and conventional entangling interaction to implement the bias-preserving CNOT gate required for claim 2, as it represents a routine technical choice for realizing gates in the very spin system platform taught by D2.
Claim 5: D1 and D2 teach the method of claim 1 but fail to teach that the correcting step uses a higher dimensional nature of the logical qudit, to correct the amplitude errors. However, D1's cat-code inherently exploits the higher-dimensional nature of the encoding Hilbert space (superpositions of coherent states) to detect and correct errors (specifically, the photon loss error which manifests as a phase error). A POSITA applying this QEC principle to the spin-cat qudits of D2 would understand that the higher-dimensional nature of the logical qudit (the spin-cat) is precisely the resource that enables error correction. Applying this resource to also correct amplitude errors (in addition to the phase errors corrected by D1's scheme) constitutes an obvious optimization and generalization of the same fundamental error correction principle disclosed by D1, tailored to the full error model of a spin system.
Claim 6: D1 and D2 teach the method of claim 5 but fail to teach comprising a step of coupling 6. the logical qubits with ancilla, and using a swap gate to swap the states. However, D1's entire QEC protocol is built upon coupling logical states with an ancilla (the transmon) for syndrome measurement and feedback (see, e.g., NPL1, Pages 2-3, 19). The swap gate is a fundamental and standard quantum gate used extensively in quantum information processing to exchange states between subsystems. It would have been obvious to a POSITA implementing the combined system to utilize a swap gate between logical qubits and ancilla systems as a routine technical method for managing and moving quantum information during the error correction and computation processes, following the architectural model provided by D1.
Claim 7: D1 and D2 teach the method of claim 1 wherein the spin system is an atomic spin system. For instance, D2 is expressly "directed to painting non-classical states of spin or motion" and provides a scheme "for generating macroscopic superposition states of a collective atomic spin" (NPL2, Abstract, Page 1). Therefore, the combination inherently teaches that the spin system is an atomic spin system.
Claim 8: D1 and D2 teach the method of claim 2 wherein the step for developing a bias-preserving CNOT gate protocol preserves the characteristic bias of noise targeted and comprises the steps of: encoding information in a ground state; promoting the encoded information to a metastable state; applying a TT -pulse between the metastable state and a Rydberg state, and to a target atom transferring the encoded information from the metastable state to the Rydberg state of the target atom; implementing an X gate in the metastable state; transferring the encoded information and a control atom from the Rydberg state back to the metastable state; and transferring the encoded information from the metastable state to the ground state. For instance, claims 2 and 3 establish it would be obvious to develop a bias-preserving CNOT gate using a neutral atom/Rydberg architecture. The specific sequence of steps recited in claim 8 (encoding in ground state, promoting to metastable/Rydberg states, applying conditional gates, transferring population) describes a conventional and standard protocol for implementing a Rydberg-blockade-mediated entangling gate in a neutral atom quantum computer. These steps represent routine technical details that a POSITA would employ to physically realize the obvious bias-preserving CNOT gate called for in claim 2 within the obvious atomic spin platform of claim 3/7.
Claim 10: D1 and D2 teach the method of claim 8 wherein the promoting step further comprises the step of: for a control atom, only the population of a |1) state is promoted to the metastable state, and for a target atom, both the population from a |0) state a |1) state are promoted to the metastable state. The recited promotion steps are standard, logical operations for constructing a controlled gate (like a CNOT) in a multi-level atomic system. Selectively promoting population based on the qubit state (|0> or |1>) is a fundamental technique for conditioning gate operation on the control qubit's value. A POSITA designing the obvious Rydberg-blockade CNOT gate of claims 2-3 and 8 would routinely and necessarily incorporate these specific population transfer steps to achieve the correct logical function
Claim 11: D1 and D2 teach the method of claim 8 wherein the implementing step further 11. comprises the step of: if the state of the control atom is in |1), an X gate is applied to the target atom, otherwise the target atom is unchanged. However, this step describes the core logical action of a CNOT gate: applying an X gate to the target if and only if the control is in the |1> state. This is the definition of the CNOT operation. It would have been obvious to a POSITA implementing the CNOT gate of the prior claims to include this definitive logical step.
Claim 12: D1 and D2 teach the method of claim 8 wherein the transferring the encoded 12. information from the metastable state to the Rydberg state of the target atom occurs only if the control atom is in a |O) state from a |1> state. However, this limitation merely reiterates the conditional logic inherent in any controlled gate protocol, such as the Rydberg blockade mechanism. This conditional behavior is the defining characteristic of the well-known Rydberg blockade effect itself. Incorporating this well-understood physical behavior into the gate protocol would have been obvious.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/GUERRIER MERANT/Primary Examiner, Art Unit 2111 1/29/2026