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CN-121638487-B - Method and device for realizing single quantum bit gate sequence

CN121638487BCN 121638487 BCN121638487 BCN 121638487BCN-121638487-B

Abstract

The application discloses a method and a device for realizing a single-quantum bit gate sequence, wherein the method comprises the following steps of responding to the gate operation in the single-quantum bit gate sequence and controlling the starting time of the single-quantum bit gate sequence And run time The following conditions are satisfied when executing At the door, , Among them, Is an integer when executing At the door, , Using time-dependent driving wave packets Applying periodic driving to the qubit, the wave packet being at time To Internal non-zero and the rest time is zero, for the wave packet Calibrating so that two are performed consecutively After the gate, the qubit is from Transition to state State, adjust integer Changing run time And determining different Selecting the corresponding gate fidelity to maximize the fidelity The value is taken as the optimal run time. The application improves the fidelity of the single quantum bit gate.

Inventors

  • ZENG YU
  • LIU QIANG

Assignees

  • 山东云海国创云计算装备产业创新中心有限公司

Dates

Publication Date
20260508
Application Date
20260130

Claims (14)

  1. 1. A method for realizing a single-quantum bit gate sequence is characterized by calibrating the resonance frequency of a quantum bit Determining its corresponding larmor period Setting the driving frequency And the qubit frequency Resonance, i.e. Constructing a time-containing Hamiltonian H (t) for realizing a single-qubit gate, wherein the Hamiltonian H (t) comprises a linear polarization period driving term resonating with the qubit, and the linear polarization period driving term consists of a time-containing wave Bao (t) and a starting time And phase phi are defined together, for which start time when any single qubit gate is implemented The method comprises the steps of restraining the single quantum bit gate to be an integral multiple of a period T of a non-RWA item in Hamiltonian, restraining the running time of the single quantum bit gate to be an integral multiple of the period T, and the method comprises the following steps: in response to each gate operation in a sequence of single qubit gates, its start time is controlled And run time At least one of the following conditions is satisfied: When executing Start time at door Run time , wherein, Is an integer; When executing Start time at door Run time ; Using time-dependent driving wave packets Applying periodic driving to the qubit, the wave packet being at time To the point of Internal non-zero, the rest of time is zero; for the wave packet Calibrating so that two are performed consecutively After the gate, the qubit is from Transition to state State, adjust integer Changing run time And determining different Selecting the corresponding gate fidelity to maximize the fidelity The value is taken as the optimal run time.
  2. 2. The method of claim 1, wherein the qubit is Fluxonium qubits.
  3. 3. The method of claim 2, wherein the using time-dependent drive wave packets Applying a periodic drive to the qubit, comprising: applying time-dependent magnetic fluxes in Fluxonium qubit Josephson junctions and inductor loops by an ac current source The said Proportional to Wherein As an envelope function, the wave packet And (3) with In direct proportion, phi represents the initial phase of the magnetic flux drive signal.
  4. 4. A method according to claim 3, wherein hamiltonian is driven Determined by the following formula: Wherein, the And In the form of a bubble-benefit matrix, To a reduction of the planck's constant, Time variable.
  5. 5. The method of claim 1, wherein the pair of wave packets Calibrating, including: By experimental measurement of two consecutive State change of the qubit after gate action; adjusting the amplitude or shape of the wave packet until it is achieved To the point of Corresponding wave packet function forms are recorded and saved as calibration parameters.
  6. 6. The method of claim 1, wherein the determining is different Corresponding gate fidelity, comprising: Construction by randomization And Sequences of gate compositions, sequences were performed and quantum state fidelity was measured, comparing different Fidelity corresponding to the value, and selecting an optimal value.
  7. 7. The method according to claim 1, wherein the method further comprises: Performing a gate operation when the qubit is at a sweet spot, wherein a magnetic flux is fixed , Is a magnetic flux quantum.
  8. 8. An apparatus for implementing a sequence of single quantum bit gates, the apparatus comprising: A setting unit for calibrating the resonance frequency of the qubit Determining its corresponding larmor period Setting the driving frequency And the qubit frequency Resonance, i.e. Constructing a time-containing Hamiltonian H (t) for realizing a single-qubit gate, wherein the Hamiltonian H (t) comprises a linear polarization period driving term resonating with the qubit, and the linear polarization period driving term consists of a time-containing wave Bao (t) and a starting time And phase phi are defined together, for which start time when any single qubit gate is implemented Constraint is carried out to ensure that the time is an integer multiple of a period T of a non-RWA item in Hamiltonian, and the running time of the single-quantum bit gate is also constrained to ensure that the running time is also an integer multiple of the period T; a control unit for controlling the start time of each gate operation in the single-qubit gate sequence And run time At least one of the following conditions is satisfied: When executing Start time at door Run time , wherein, Is an integer; When executing Start time at door Run time ; A driving unit for using the time-containing driving wave packet Applying periodic driving to the qubit, the wave packet being at time To the point of Internal non-zero, the rest of time is zero; a calibration unit for the wave packet Calibrating so that two are performed consecutively After the gate, the qubit is from Transition to state A state; a selecting unit for adjusting an integer Changing run time And determining different Selecting the corresponding gate fidelity to maximize the fidelity The value is taken as the optimal run time.
  9. 9. The apparatus of claim 8, wherein the qubit is Fluxonium qubits.
  10. 10. The apparatus of claim 9, wherein the drive unit is further configured to: applying time-dependent magnetic fluxes in Fluxonium qubit Josephson junctions and inductor loops by an ac current source The said Proportional to Wherein As an envelope function, the wave packet And (3) with In direct proportion, phi represents the initial phase of the magnetic flux drive signal.
  11. 11. The apparatus of claim 10, wherein the hamiltonian is driven Determined by the following formula: Wherein, the And In the form of a bubble-benefit matrix, To a reduction of the planck's constant, Time variable.
  12. 12. The apparatus of claim 8, wherein the calibration unit is further configured to: By experimental measurement of two consecutive State change of the qubit after gate action; adjusting the amplitude or shape of the wave packet until it is achieved To the point of Corresponding wave packet function forms are recorded and saved as calibration parameters.
  13. 13. The apparatus of claim 8, wherein the pick unit is further configured to: Construction by randomization And Sequences of gate compositions, sequences were performed and quantum state fidelity was measured, comparing different Fidelity corresponding to the value, and selecting an optimal value.
  14. 14. The apparatus of claim 8, wherein the control unit is further configured to: Performing a gate operation when the qubit is at a sweet spot, wherein a magnetic flux is fixed , Is a magnetic flux quantum.

Description

Method and device for realizing single quantum bit gate sequence Technical Field The application relates to the technical field of superconducting quantum computing, in particular to a method and a device for realizing a single-quantum bit gate sequence for controlling superconducting quantum bits with high fidelity. Background Quantum computing uses quantum mechanical properties for information processing, and its basic unit is a qubit. Quantum gates are basic operations that act on qubits through which a quantum circuit can be built to perform quantum algorithms. In superconducting quantum computing, a single-qubit gate is typically implemented by microwave or magnetic flux driving that applies resonance to the vector qubits, inducing a rabi oscillation. Conventional implementations typically rely on a rotation wave approximation (Rotating Wave Approximation, RWA), i.e., ignoring the high frequency oscillation term in hamiltonian when the drive frequency resonates with the qubit frequency and the drive strength is much smaller than the qubit frequency. This approximation is true when driving is weak, but when high-speed quantum gate operation is pursued, the driving strength increases, and the rotation wave approximation fails, resulting in a decrease in gate operation fidelity. For the Fluxonium superconducting qubits with high non-harmony, the qubit frequency is generally lower, so that the application condition of the rotating wave approximation is more severe, and the improvement of the door operation speed is limited. In addition, the conventional scheme requires a separate calibration of the door operation rotating about the X-axis and the Y-axis, which is cumbersome. Disclosure of Invention The application provides a method and a device for realizing a single-quantum bit gate sequence, electronic equipment and a storage medium, which are used for at least solving the technical problems in the prior art. According to a first aspect of the present application, there is provided a method of implementing a single qubit gate sequence to calibrate the resonance frequency of a qubitDetermining its corresponding larmor periodSetting the driving frequencyAnd the qubit frequencyResonance, i.e.The method comprises the following steps: in response to each gate operation in a sequence of single qubit gates, its start time is controlled And run timeAt least one of the following conditions is satisfied: When executing Start time at doorRun time, wherein,Is an integer; When executing Start time at doorRun time; Using time-dependent driving wave packetsApplying periodic driving to the qubit, the wave packet being at timeTo the point ofInternal non-zero, the rest of time is zero; for the wave packet Calibrating so that two are performed consecutivelyAfter the gate, the qubit is fromTransition to stateState, adjust integerChanging run timeAnd determining differentSelecting the corresponding gate fidelity to maximize the fidelityThe value is taken as the optimal run time. In some alternative embodiments, the qubit is Fluxonium qubits. In some alternative embodiments, the using time-dependent drive wave packetsApplying a periodic drive to the qubit, comprising: applying time-dependent magnetic fluxes in Fluxonium qubit Josephson junctions and inductor loops by an ac current source The saidProportional toWhereinAs an envelope function, the wave packetAnd (3) withIn direct proportion, phi represents the initial phase of the magnetic flux drive signal. In some alternative embodiments, the hamiltonian is drivenDetermined by the following formula: Wherein, the AndIn the form of a bubble-benefit matrix,To a reduction of the planck's constant,Time variable. In some alternative embodiments, the pair of wave packetsCalibrating, including: By experimental measurement of two consecutive State change of the qubit after gate action; adjusting the amplitude or shape of the wave packet until it is achieved To the point ofCorresponding wave packet function forms are recorded and saved as calibration parameters. In some alternative embodiments, the determination is differentCorresponding gate fidelity, comprising: Construction by randomization AndSequences of gate compositions, sequences were performed and quantum state fidelity was measured, comparing differentFidelity corresponding to the value, and selecting an optimal value. In some alternative embodiments, the method further comprises: Performing a gate operation when the qubit is at a sweet spot, wherein a magnetic flux is fixed ,Is a magnetic flux quantum. According to a second aspect of the present application, there is provided an implementation apparatus of a single-qubit gate sequence, comprising: A setting unit for calibrating the resonance frequency of the qubit Determining its corresponding larmor periodSetting the driving frequencyAnd the qubit frequencyResonance, i.e.; A control unit for controlling the start time of each gate operation in the single-qubit gate sequenc