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 .
Status of Claims
This Office Action is in response to the communication filed on 17 November 2023.
Claims 1-30 are being considered on the merits.
Information Disclosure Statement
The information disclosure statement (IDS) submitted on 30 Sept 2024 has been considered. The submission is in compliance with the provisions of 37 CFR 1.97. Accordingly, initialed and dated copies of Applicant's IDS forms 1499 is attached to the instant Office action.
Claim Rejections - 35 USC § 112
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.
The following is a quotation of 35 U.S.C. 112 (pre-AIA ), second paragraph:
The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.
Claim 9 is rejected under 35 U.S.C. 112(b) or 35 U.S.C. 112 (pre-AIA ), second paragraph, as being indefinite for failing to particularly point out and distinctly claim the subject matter which the inventor or a joint inventor (or for applications subject to pre-AIA 35 U.S.C. 112, the applicant), regards as the invention.
Claim 9 recites the limitation " the leakage information transition jumps" in the third limitation of the claim.
There is insufficient antecedent basis for this limitation in the claim.
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.
Claims 1-3 are rejected under 35 U.S.C. 103 as being unpatentable over Huang, W., Yang, C.H., Chan, K.W. et al. (“Fidelity benchmarks for two-qubit gates in silicon”. Nature 569, 532–536 (2019). https://doi.org/10.1038/s41586-019-1197-0; hereinafter, “Huang”) in view of Pesetski, et. al. (US 2012/0159272 A1; hereinafter “Pesetski”)
Claim 1:
A method for determining fidelity of a qubit gate in a quantum processor, comprising (Pesetski, para. 0026: “The quantum processor 110 further comprises a plurality of qubit cells AB1-AB5, BC1-BC5, CD1-CD5, DE1-DE5, B12-D12, B23-D23, B34-D34, B45-D45, X1-X3, and R1-R3 configured to perform logical operations on the stored quantum information”): determining environmental qubit gates associated with a two-qubit gate in the quantum processor, wherein the two-qubit gate interacts with the environmental qubit gates in the quantum processor; (Huang, fig. 1: “False-colour scanning electron microscope image of the device. Two quantum dots, D1 and D2, are formed underneath gates G1 (blue) and G2 (red). The gates CB (dark purple), G3 and G4 (grey) form confinement barriers that laterally define the quantum dots.”)
determining a fidelity error of the environmental qubit gates based on a fidelity error of the two-qubit gate; (Huang, pg. 534: “Tomographic characterization of quantum gates, such as Bell state tomography, is convenient to implement as it requires comparatively short sequences of pulses (see, for example, Fig. 3a). It produces a first estimate of the fidelities in the system; however, disentangling gate errors from state preparation and measurement (SPAM) errors can be rather imprecise, making the quantification of gate fidelities >99% almost impossible.”)
determining frequency of the environmental qubit gates (Huang, pg. 534: “To achieve single-qubit control independently of the state of the other qubit, we need to apply a two-frequency resonance pulse (for example, U1↑U1↓), which yields a X/2 gate for a π/2-rotation” Examiner notes determining is defined as causing something to occur such that Huang teaches applying i.e. causing a two-frequency resonance pulse to occur) based on the fidelity error of the environmental qubit gates; and (Huang, pg. 534: “The fidelities reported here are comparable to the those reported (78% in ref. 15 and 85%–89% in ref. 14).”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates. (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang. Huang teaches two-qubit fidelities near the fault-tolerance threshold in superconductor systems; Pesetski teaches improving fidelity of a quantum operation on a quantum bit. One of ordinary skill would have been motivated to combine the teachings of Pesetski into Huang in order to improve fidelity of a quantum operation in order to solve a large class of problems with exponentially greater efficiency than that of a classical computer (Pesetski, para. 0002).
Claim 2:
The method according to claim 1, wherein determining the fidelity error of the environmental qubit gates based on the fidelity error of the two-qubit gate comprises: decomposing the fidelity error of the two-qubit gate into different environmental qubit gates, so as to obtain the fidelity error of the different environmental qubit gates. (Huang, abstract: “Two-qubit gates have now been demonstrated in a number of systems13,14,15, but as yet an accurate assessment of their fidelities using Clifford-based randomized benchmarking, which uses sequences of randomly chosen gates to measure the error, has not been achieved. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80 to 89 per cent, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7 per cent and an average controlled-rotation fidelity of 98 per cent.”)
Claim 3:
The method according to claim 1, wherein determining the frequency of the environmental qubit gates based on the fidelity error of the environmental qubit gates comprises: scanning a superconducting circuit of the quantum processor to obtain a plurality of parameters; and (Pesetski, para. 0019 and 0021: “In a sweep, the qubit state tracks the energy contour of the system as the control parameter is adjusted.” “For example, a physical implementation of any of the plurality of qubits 12 and 14 may be a Josephson junction, a quantum dot, a SQUID (superconducting quantum interference device), a Cooper pair box, or an ion trap”)
determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters. (Huang, pg. 534-535: “ The fitting parameters A and B absorb the SPAM errors, leaving rC as the error per Clifford gate. We obtain a Clifford gate fidelity of FClifford = 1 − rC = 94.7% ± 0.8%, and a primitive gate fidelity of Fprimitive = 98.0% ± 0.3%.”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
Claims 4-12 are rejected under 35 U.S.C. 103 as being unpatentable over Huang in view of Pesetski, and further in view of Arute, F., Arya, K., Babbush, R. et al. (“Quantum supremacy using a programmable superconducting processor.” Nature 574, 505–510 (2019). https://doi.org/10.1038/s41586-019-1666-5; hereinafter, “Arute”)
Claim 4:
The method according to claim 3, wherein the plurality of parameters comprise single-qubit parameters, (Pesetski, para. 0020: “The coupling between each qubits (e.g., 12) and its corresponding classical control (e.g., 32) is arranged so that the quantum state of qubit 12 may be changed in response to adjustment of a classical control parameter associated with the digital control”)
wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining the frequency of the environmental qubit gates and frequency of a coupler corresponding to the fidelity error of the environmental qubit gates based on the single-qubit parameters; and (Arute, pg. 506 and fig. 1: “The qubit is encoded as the two lowest quantum eigenstates of the resonant circuit. Each transmon has two controls: a microwave drive to excite the qubit, and a magnetic flux control to tune the frequency…As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler31,32. Our coupler design allows us to quickly tune the qubit–qubit coupling from completely off to 40 MHz.”)
wherein determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates comprises: determining the fidelity of the two-qubit gate based on the frequency of the environmental qubit gates (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”) and the frequency of the coupler. (Arute, pg. 506 and fig. 1: “As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler31,32. Our coupler design allows us to quickly tune the qubit–qubit coupling from completely off to 40 MHz.”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified. Arute teaches use of a processor with programmable superconducting qubits. One of ordinary skill would have been motivated to combine the teachings of Arute into Huang, as modified in order to run quantum algorithms in an exponentially large computational space (Arute, abstract).
Claim 5:
The method according to claim 3, wherein the plurality of parameters comprise a number of single-qubit states in a multi-qubit model, (Pesetski, para. 0028: “The plurality of qubit cells can include multiple types of qubit cells, each having a different structure and optimized for a different function. For example, a first set of qubit cells X1-X3 can be optimized for performing a quantum rotation, such as a Hadamard gate or an X gate operation, on a coupled resonator (e.g., B1-D1). To this end, each of the first set of qubit cells is configured to have a set of energy states that can be modeled as the state of a spin-½ particle, with associated “spin-up” and “spin-down” states that interact differently with an associated classical control parameter. In one implementation, the first set of qubit cells can be constructed as a superconducting flux qubit.”)
wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining the frequency of the environmental qubit gates (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”) and frequency of a coupler corresponding to the fidelity error of the environmental qubit gates based on the number of the single-qubit states in the multi-qubit model; and (Arute, pg. 506 and fig. 1: “As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler31,32. Our coupler design allows us to quickly tune the qubit–qubit coupling from completely off to 40 MHz.”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates comprises: determining a fidelity corresponding to the frequency of the environmental qubit gates (Arute, pg. 507: “We perform two-qubit iSWAP-like entangling gates by bringing neigh bouring qubits on-resonance and turning on a 20-MHz coupling for 12 ns, which allows the qubits to swap excitations. During this time, the qubits also experience a controlled-phase (CZ) interaction, which originates from the higher levels of the transmon. The two-qubit gate frequency trajectories of each pair of qubits are optimized to mitigate the same error mechanisms considered in optimizing single-qubit operation frequencies”) and the frequency of the coupler as the fidelity of the two-qubit gate. (Arute, pg. 506 and fig. 1: “The qubit is encoded as the two lowest quantum eigenstates of the resonant circuit. Each transmon has two controls: a microwave drive to excite the qubit, and a magnetic flux control to tune the frequency…As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler31,32. Our coupler design allows us to quickly tune the qubit–qubit coupling from completely off to 40 MHz.”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified, as set forth above with respect to claim 3.
Claim 6:
The method according to claim 3, wherein the plurality of parameters comprise an offset local extremum, wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining a real local extremum based on the offset local extremum; and (Huang, methods: “After this sequence we perform one of four pre-measurement rotations Rp = {I, X/2, −X/2, Y/2, −Y/2} to achieve projective measurements in the Z, Y, −Y, −X, and X bases, respectively. Although the projection outcome on the −X and −Y bases contains redundant information, it is useful to cancel out offset errors. The two-qubit density matrix ρ is reconstructed from the combined 25 projection axes with 800 repetitions using maximum likelihood estimation.”)
determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the real local extremum; and (Huang, extended data fig. 2: “Frequency calibration of the ESR frequencies is implemented by interleaving calibration sequences with the randomized benchmarking experiment. After acquisition of three random sequences (one sequence is repeated 125 times), we check if the ESR frequency is still on-resonance by applying a low-power (26 dB lower than the typical operating power) π-rotation. If the spin-up probability is above the threshold of 50% of the readout visibility, the experiment will continue. If the spin-up probability is below the threshold, the resonance frequency will be recalibrated until all ESR frequencies pass the check, and the measurement will continue.”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates comprises: determining a fidelity corresponding to the frequency of the environmental qubit gates as the fidelity of the two-qubit gate. (Huang fig. 2 and pg. 535: “In conclusion, we have shown that the full two-qubit Clifford gate set can be constructed purely using magnetic resonance pulses acting on silicon spin qubits, and have used this to obtain the two-qubit gate fidelity using randomized benchmarking. The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz). Higher Rabi frequencies can act as a remedy, and Rabi frequencies as high as 30 MHz have recently been demonstrated using electric-dipole spin resonance techniques in silicon devices, while barely affecting (ref. 17).”)
Claim 7:
The method according to claim 3, wherein the plurality of parameters comprise a basis vector, wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining an evolution result of the quantum processor in the basis vector; and (Pesetski, para. 0019: “A “jump” takes advantage of symmetries of the qubit Hamiltonian to instantaneously change the energy of the system without changing the state. In a jump, the control parameter is rapidly swept from one point to another in which the qubit has the same energy eigenstate but may or may not have the same eigenvalue” Examiner notes Huang teaches a Hamiltonian where the qubit is represented by a vector i.e. a basis vector and a jump i.e. an evolution of the system i.e. processor).
determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”) based on the evolution result, (Pesetski, para. 0019 teaches an evolution result in the form of an energy change without a state change which may be subsequently used).
wherein a magnitude of the fidelity error of the environmental qubit gates is less than a magnitude threshold. (Huang, abstract: “Although various qubit systems have shown high fidelities at the one-qubit level4,5,6,7,8,9,10, the only solid-state qubits manufactured using standard lithographic techniques that have demonstrated two-qubit fidelities near the fault-tolerance threshold6 have been in superconductor systems”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
Claim 8:
The method according to claim 7, wherein the plurality of parameters comprise waveform parameters, and (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
the waveform parameters are maximum value points determined based on the evolution result, (Pesetski, para. 0019: “To establish some terminology, the term “sweep” is intended to refer to an adiabatic sweeps of a qubit control parameter, in which the control parameter is adjusted slowly relative to an energy of a splitting between energy states of a system. In a sweep, the qubit state tracks the energy contour of the system as the control parameter is adjusted. The fidelity of a sweep can be made arbitrarily high by lowering the sweep rate. A “jump” takes advantage of symmetries of the qubit Hamiltonian to instantaneously change the energy of the system without changing the state. In a jump, the control parameter is rapidly swept from one point to another in which the qubit has the same energy eigenstate but may or may not have the same eigenvalue. The fidelity of a jump can be made arbitrarily high by increasing the sweep rate.” Pesetski teaches a maximum point as a second point maximally in which the qubit has the same energy eigenstate i.e. the result must be the same energy eigenstate).
wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the waveform parameters. (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
Claim 9:
The method according to claim 7, wherein the plurality of parameters comprise a local maximum value of the evolution result, (Pesetski, para. 0019 teaches a local maximum value as the result in the form of an energy change without a state change which may be subsequently used)
wherein determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates based on the plurality of parameters comprises: determining leakage information of the quantum processor at the local maximum value; and (Arute, pg. 509: “To be successfully described by a digitized error model, a system should be low in correlated errors. We achieve this in our experiment by choosing circuits that randomize and decorrelate errors, by optimizing control to minimize systematic errors and leakage, and by designing gates that operate much faster than correlated noise sources, such as 1/f flux noise37”)
determining a qubit state to which the environmental qubit gates corresponding to the leakage information transition jumps (Arute, pg. 509: “To be successfully described by a digitized error model, a system should be low in correlated errors. We achieve this in our experiment by choosing circuits that randomize and decorrelate errors, by optimizing control to minimize systematic errors and leakage, and by designing gates that operate much faster than correlated noise sources, such as 1/f flux noise37”; Examiner notes “leakage information transition jumps” lacks antecedent precedent. As a result, for examination purposes only, this limitation is interpreted as “corresponding to the leakage information”), and determining the frequency of the environmental qubit gates corresponding to the fidelity error of the environmental qubit gates in the qubit state; and (Arute, pg. 507: “We perform two-qubit iSWAP-like entangling gates by bringing neigh bouring qubits on-resonance and turning on a 20-MHz coupling for 12 ns, which allows the qubits to swap excitations. During this time, the qubits also experience a controlled-phase (CZ) interaction, which originates from the higher levels of the transmon. The two-qubit gate frequency trajectories of each pair of qubits are optimized to mitigate the same error mechanisms considered in optimizing single-qubit operation frequencies”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates comprises: determining the fidelity corresponding to the frequency of the environmental qubit gates as the fidelity of the two-qubit gate. (Huang fig. 2 and pg. 535: “In conclusion, we have shown that the full two-qubit Clifford gate set can be constructed purely using magnetic resonance pulses acting on silicon spin qubits, and have used this to obtain the two-qubit gate fidelity using randomized benchmarking. The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz). Higher Rabi frequencies can act as a remedy, and Rabi frequencies as high as 30 MHz have recently been demonstrated using electric-dipole spin resonance techniques in silicon devices, while barely affecting (ref. 17).”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified, as set forth above with respect to claim 3.
Claim 10:
The method according to claim 1, wherein the quantum processor comprises inductively- coupled fluxonium-type qubits, or the quantum processor comprises transmon-type qubits. (Arute, pg. 506: “We designed a quantum processor named ‘Sycamore’ which consists of a two-dimensional array of 54 transmon qubits, where each qubit is tunably coupled to four nearest neighbours, in a rectangular lattice.”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified, as set forth above with respect to claim 3.
Claim 11:
A method for determining fidelity of a qubit gate in a quantum processor, comprising: acquiring, by invoking a first interface (Arute, pg. 506: “We designed a quantum processor named ‘Sycamore’ which consists of a two-dimensional array of 54 transmon qubits, where each qubit is tunably coupled to four nearest neighbours, in a rectangular lattice”), environmental qubit gates associated with a two-qubit gate in the quantum processor, (Huang, fig. 1: “False-colour scanning electron microscope image of the device. Two quantum dots, D1 and D2, are formed underneath gates G1 (blue) and G2 (red). The gates CB (dark purple), G3 and G4 (grey) form confinement barriers that laterally define the quantum dots.”)
wherein the first interface comprises a first parameter, a parameter value of the first parameter involves the two-qubit gate and the environmental qubit gates, (Huang, pg. 534-535: “ The fitting parameters A and B absorb the SPAM errors, leaving rC as the error per Clifford gate. We obtain a Clifford gate fidelity of FClifford = 1 − rC = 94.7% ± 0.8%, and a primitive gate fidelity of Fprimitive = 98.0% ± 0.3%.” “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
wherein the two-qubit gate interacts with the environmental qubit gates in the quantum processor; (Huang, fig. 1: “False-colour scanning electron microscope image of the device. Two quantum dots, D1 and D2, are formed underneath gates G1 (blue) and G2 (red). The gates CB (dark purple), G3 and G4 (grey) form confinement barriers that laterally define the quantum dots.”)
determining a fidelity error of the environmental qubit gates based on a fidelity error of the two-qubit gate; (Huang, pg. 534: “Tomographic characterization of quantum gates, such as Bell state tomography, is convenient to implement as it requires comparatively short sequences of pulses (see, for example, Fig. 3a). It produces a first estimate of the fidelities in the system; however, disentangling gate errors from state preparation and measurement (SPAM) errors can be rather imprecise, making the quantification of gate fidelities >99% almost impossible.”)
determining frequency of the environmental qubit gates (Huang, pg. 534: “To achieve single-qubit control independently of the state of the other qubit, we need to apply a two-frequency resonance pulse (for example, U1↑U1↓), which yields a X/2 gate for a π/2-rotation” Examiner notes determining is defined as causing something to occur such that Huang teaches applying i.e. causing a two-frequency resonance pulse to occur) based on the fidelity error of the environmental qubit gates; and (Huang, pg. 534: “The fidelities reported here are comparable to the those reported (78% in ref. 15 and 85%–89% in ref. 14).”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates; and (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
outputting, by invoking a second interface (Arute, pg. 506: “Each qubit is connected to a linear resonator used to read out the qubit state”), the fidelity of the two-qubit gate, (Huang, abstract: “Two-qubit gates have now been demonstrated in a number of systems13,14,15, but as yet an accurate assessment of their fidelities using Clifford-based randomized benchmarking, which uses sequences of randomly chosen gates to measure the error, has not been achieved. Here, for qubits encoded on the electron spin states of gate-defined quantum dots, we demonstrate Bell state tomography with fidelities ranging from 80 to 89 per cent, and two-qubit randomized benchmarking with an average Clifford gate fidelity of 94.7 per cent and an average controlled-rotation fidelity of 98 per cent.”)
wherein the second interface comprises a second parameter, and a parameter value of the second parameter represents the fidelity of the two-qubit gate. (Arute, pg. 506: “A key systems engineering advance of this device is achieving high-fidelity single- and two-qubit operations…Each qubit is connected to a linear resonator used to read out the qubit state5. As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler31,32.”)
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified, as set forth above with respect to claim 3.
Claim 12:
A method for determining fidelity of a qubit gate in a quantum processor, comprising: acquiring, from a quantum platform, (Pesetski, para. 0019 and 0021: “In a sweep, the qubit state tracks the energy contour of the system as the control parameter is adjusted.” “For example, a physical implementation of any of the plurality of qubits 12 and 14 may be a Josephson junction, a quantum dot, a SQUID (superconducting quantum interference device), a Cooper pair box, or an ion trap”) environmental qubit gates associated with a two-qubit gate in the quantum processor, (Arute, pg. 507: “We perform two-qubit iSWAP-like entangling gates by bringing neigh bouring qubits on-resonance and turning on a 20-MHz coupling for 12 ns, which allows the qubits to swap excitations. During this time, the qubits also experience a controlled-phase (CZ) interaction, which originates from the higher levels of the transmon. The two-qubit gate frequency trajectories of each pair of qubits are optimized to mitigate the same error mechanisms considered in optimizing single-qubit operation frequencies”)
wherein the two-qubit gate interacts with the environmental qubit gates in the quantum processor; (Huang, fig. 1: “False-colour scanning electron microscope image of the device. Two quantum dots, D1 and D2, are formed underneath gates G1 (blue) and G2 (red). The gates CB (dark purple), G3 and G4 (grey) form confinement barriers that laterally define the quantum dots.”)
determining a fidelity error of the environmental qubit gates based on a fidelity error of the two-qubit gate; (Huang, pg. 534: “Tomographic characterization of quantum gates, such as Bell state tomography, is convenient to implement as it requires comparatively short sequences of pulses (see, for example, Fig. 3a). It produces a first estimate of the fidelities in the system; however, disentangling gate errors from state preparation and measurement (SPAM) errors can be rather imprecise, making the quantification of gate fidelities >99% almost impossible.”)
determining frequency of the environmental qubit gates (Huang, pg. 534: “To achieve single-qubit control independently of the state of the other qubit, we need to apply a two-frequency resonance pulse (for example, U1↑U1↓), which yields a X/2 gate for a π/2-rotation” Examiner notes determining is defined as causing something to occur such that Huang teaches applying i.e. causing a two-frequency resonance pulse to occur) based on the fidelity error of the environmental qubit gates; and (Huang, pg. 534: “The fidelities reported here are comparable to the those reported (78% in ref. 15 and 85%–89% in ref. 14).”)
determining fidelity of the two-qubit gate based on the frequency of the environmental qubit gates; and (Huang, pg. 535: “The two qubits can be controllably entangled, as demonstrated by the generation of the four Bell states with fidelities of F = 80%–89% and concurrences between 0.78 and 0.82. We measured a two-qubit gate fidelity of FClifford = 94.7% ± 0.8%, which translates into Fprimitive = 98.0% ± 0.3% for the primitive gates that include the CROT with a platform-independent protocol. We identify the main source of infidelity in our experiment to be dephasing, which occurs at a rate that is only one order of magnitude lower than our Rabi frequency (about 410 kHz).”)
returning the fidelity of the two-qubit gate to the quantum platform. (Arute, fig. 4: “Here, the two-qubit gates are applied in a simplifiable tiling and sequence such that the full circuits can be simulated out to n = 53, m = 14 in a reasonable amount of time…The corresponding full circuit data, not simulated but archived, is expected to show similarly statistically significant fidelity” Examiner notes that Fig 4 demonstrates a quantum circuit for verifying quantum processor).
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Pesetski into Huang as set forth above with respect to claim 1.
It would have obvious to one of ordinary skill in the art before the effective filing date of the present application to combine the teachings of Arute into Huang, as modified, as set forth above with respect to claim 3.
Prior Art
C. J. Balance, et. al. (arXiv:1406.5473v1 [quant-ph] 20 Jun 2014) teaches the speed/fidelity trade-off for a two-qubit phase gate implemented in 43Ca+ hyperfine trapped-ion qubits.
Watson, T., Philips, S., Kawakami, E. et al. (“A programmable two-qubit quantum processor in silicon.” Nature 555, 633–637 (2018). https://doi.org/10.1038/nature25766) teaches control techniques to demonstrate a programmable two-qubit quantum processor in a silicon device that can perform the Deutsch–Josza algorithm and the Grover search algorithm—canonical examples of quantum algorithms that outperform their classical analogues
Search Notes
PE2E search notes most relevant: L14 CPC with keywords “qubit” “gates” frequency” “fidelity” “error” “local” “maximum” “processor” “vector”
IP.com search most relevant with date filter: “fidelity of a qubit gate”
Conclusion
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/STL/Examiner, Art Unit 2147
/VIKER A LAMARDO/Supervisory Patent Examiner, Art Unit 2147
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