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 .
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.
This application currently names joint inventors. In considering patentability of the claims the examiner presumes that the subject matter of the various claims was commonly owned as of the effective filing date of the claimed invention(s) absent any evidence to the contrary. Applicant is advised of the obligation under 37 CFR 1.56 to point out the inventor and effective filing dates of each claim that was not commonly owned as of the effective filing date of the later invention in order for the examiner to consider the applicability of 35 U.S.C. 102(b)(2)(C) for any potential 35 U.S.C. 102(a)(2) prior art against the later invention.
Claims 1-7,9-16 and 18-20 are rejected under 35 U.S.C. 103 as being unpatentable over Parrado-Rodríguez, Pedro, et al. "Crosstalk suppression for fault-tolerant quantum error correction with trapped ions." Quantum 5 (2021): 487 [hereinafter Parrado-Rodríguez] and further in view of L. N. Egan, Scaling quantum computers with long chains of trapped ions, Ph.D. thesis, 2021 [hereinafter Egan].
Regarding Claim 1 and 10 and 19:
Parrado-Rodríguez teaches a method for suppressing crosstalk in a quantum circuit of a quantum computing system using local controls (Section 4. Active Suppression of crosstalk for QEC), comprising:
selecting, from a plurality ions in an ion trap implementing the quantum circuit, a pair of target ions on which to perform a quantum gate operation (section 4.1 – application of MS/2 gate to a pair of active ions), wherein the plurality of ions corresponds to a respective plurality of qubits in the quantum circuit (abstract);
performing the quantum gate operation on the pair of target qubits (section 4.1 – application of MS/2 gate to a pair of active ions); and
inducing a rotation on at least one of ions such that crosstalk between any of the target ions and any other of the plurality of ions in the ion trap resulting from the performance of the quantum gate operation is canceled out (section 4.1 – a π rotation about Z axis on all spectator ions).
However, in Parrado-Rodríguez, the rotation is applied to all of the spectator ions, not the active “target” ions. This rotation operation is taught to eliminate crosstalk between the active ions and the spectator ions via a refocusing technique. Specifically, Parrado-Rodríguez 4.1 states,
Our refocussing technique consists of the application of (i) a half entangling gate (MS/2) between the pair of active ions (i,j) ∈ G, which corresponds to XXij(θ/2) in Eq. (3) for θ = π/2, (ii) a π-rotation about the Z axis on (all) the spectator ions(s) n ∈ neig{G}, which corresponds to Zn(θ) in Eq. (1) with θ = π. (iii) A second half-entangling gate (MS/2) on the active ions, and (iv) final π-rotation(s) about the Z axis of the spectator ion(s). It is straightforward to verify that, if implemented flawlessly, this composite sequence cancels the crosstalk interaction between gate and spectator qubits, while it realises the intended MS gate on the gate qubits.”
Further, Egan notes that applying a π-rotation between successive gates, or as it is phrased therein an “echo sequence,” will “suppress other forms of coherent errors, such as gate crosstalk.” Pg 141.
So the teaching of Parrado-Rodríguez is that crosstalk between the target ions and the spectator ions can be cancelled by applying an echo sequence of π-rotation to the spectator ions. Furthermore, the teaching of Egan explains that echo sequences suppress coherent errors to the extent that errors are stable between gate applications. Inverting the operation of Parrado-Rodríguez, i.e. π-rotating all of the active ions instead of the spectator ions, would only entail changing the target of the laser from the spectator ions to the active ions. This small change in operations uses the same mathematically model of crosstalk cancellation, since each π-rotation of all of the target ions would cancel coherent crosstalk between the target ions and the spectator ions in the same fashion as before, and in the fashion that Egan explains. This result would predictably yield the same cancellation of crosstalk, because the same physical mechanism of reversing crosstalk after the π-rotation would apply.
As such, it would have been obvious to one of ordinary skill in the art before the effective time of filing to change the refocusing scheme of Parrado-Rodríguez such that the π-rotation are applied to all of (both) the active ions while leaving the spectator ions alone. One would have been motivated to do so since the inverting the operators disclosed in Parrado-Rodríguez would yield a predictable result to one of ordinary skill in the art, i.e., cancelling out crosstalk between the active and spectator ions, since Egan and Parrado-Rodríguez explain that coherent crosstalk created in a first gate would be suppressed by the combination of a π-rotation and a re-application of said first gate.
Further, it is not specified that Parrado-Rodríguez uses one or more processors; and
a memory storing program code having a plurality of instructions, which, when executed by the one or more processors, causes the quantum computing system to perform the above steps. However, it is heavily implied that this is the case, as the publication is replete with references to simulations and calculations that would be virtually impossible to perform without the aid of a computer and appropriate programming. Accordingly, it would have been obvious to one of ordinary skill in the art before the effective time of filing to use a computer and code in memory to execute the above noted steps, since automating such steps is suggested by the publication and a self-evident improvement.
Regarding Claim 2 and 11:
The above modified invention teaches the method of claim 1, wherein the quantum gate operation is a quantum entanglement gate operation (Parrado-Rodríguez MS gate is a quantum entanglement gate operation).
Regarding Claim 3 and 12:
The above modified invention teaches the method of claim 1, wherein inducing the rotation on each of the target qubits comprises inducing a π-rotation on each of the target ions (Parrado-Rodríguez as discussed above, the proposed modification if applying the π-rotation of section 4.1 to the target ions rather than the spectator ions).
Regarding Claim 4 and 13 and 20:
The above modified invention teaches the method of claim 3, wherein inducing the π-rotation on each of the target ions comprises inserting the π-rotation along a Z-axis of an entangling gate associated with the quantum gate operation (Parrado-Rodríguez section 4.1).
However, Parrado-Rodríguez fails to teach providing such a rotation about the Y-axis. Switching from the Z to the Y axis is an obvious modification, and since the difference in the Z and Y directions is essentially arbitrary. As such, it would have been obvious to one of ordinary skill in the art before the effective time of filing to rotate about the Y axis of Parrado-Rodríguez rather than the Z axis. One would have been motivated to do so since the axes are equivalent and as such would yield a predictable result to one of ordinary skill in the art, i.e., flipping the qubits with respect to the X axis.
Regarding Claim 5 and 14:
The above modified invention teaches the method of claim 1, further comprising, receiving quantum state information of the quantum circuit (Parrado-Rodríguez section 4.1).
Regarding Claim 6 and 15:
The above modified invention teaches the method of claim 1, wherein inducing the rotation on at least one of the target qubits comprises inducing the rotation on each of the target qubits (as discussed above, the crosstalk cancellation of Parrado-Rodríguez only works to the extent that all of ions in either the active or spectator group are rotated).
Regarding Claim 7 and 16:
The above modified invention teaches the method of claim 1, wherein the quantum computing system is an ion trap quantum computing system (Parrado-Rodríguez abstract).
Regarding Claim 9 and 18:
The above modified invention teaches the method of claim 8, wherein inducing the rotation on the target qubits comprises:
configuring one or more tuning parameters to generate echoing pulses sufficient to drive one or more rotations on the target ions (Parrado-Rodríguez section 4.1 “composite pulse schemes to refocus”); and
applying the echoing pulses to the target ions (Parrado-Rodríguez section 4.1).
Response to Arguments
Applicant’s arguments and amendments with respect to the 112(a) and 101 rejections of record have been fully considered and are persuasive. Those rejections have been withdrawn.
Applicant argues that the proposed inversion of Parrado-Rodríguez would not provide the same benefit as the claimed invention. This is not persuasive. As noted above, Parrado-Rodríguez teaches applying a π-rotation to all spectator ions. A simple inversion of this process would entail applying a π-rotation to all (both) of the target ions instead. Such an inversion would not suppress crosstalk between the target ions, but rather would suppress crosstalk between the rotated targets ions and the non-rotated spectator ion(s).
It is noted that the instant inventors appeared to have recognized the teachings of Parrado-Rodríguez and Egan with respect to crosstalk cancellation in their other published work. See e.g., Fang, Chao, et al. "Crosstalk suppression in individually addressed two-qubit gates in a trapped-ion quantum computer." Physical Review Letters 129.24 (2022): 240504.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). 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.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to WYATT A STOFFA whose telephone number is (571)270-1782. The examiner can normally be reached M-F 0700-1600 EST.
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WYATT STOFFA
Primary Examiner
Art Unit 2881
/WYATT A STOFFA/Primary Examiner, Art Unit 2881
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