Method for determining crosstalk coefficient of quantum bit driving line and storage medium

Abstract

The invention discloses a quantum bit drive line crosstalk coefficient determination method and a storage medium, and belongs to the technical field of quantum computing. The method comprises the following steps: presetting a plurality of groups of amplitude crosstalk coefficients and phase crosstalk coefficients of a target quantum bit; determining a plurality of target working frequencies of the target quantum bit according to the plurality of groups of amplitude crosstalk coefficients, the phase crosstalk coefficients and the corresponding relationship between the working frequencies of the quantum bits and the amplitude crosstalk coefficients and the phase crosstalk coefficients; executing a Rabian oscillation experiment on the target quantum bit to obtain the measurement working frequency of the target quantum bit; and determining the amplitude crosstalk coefficient and the phase crosstalk coefficient when the target working frequency is the same as the measurement working frequency as the crosstalk coefficient of the target quantum bit. According to the method, the crosstalk influence of the microwave signals applied to the driving lines of the target quantum bits on the driving lines of the other quantum bits can be rapidly determined so as to perform calibration or compensation, the operation process is simple, and time and labor are saved.

Description

Technical Field

[0001] This application relates to the field of quantum computing technology, and in particular to a method for determining the crosstalk coefficient of a qubit driving line and a storage medium. Background Technology

[0002] A quantum computer is a physical device that performs high-speed mathematical and logical operations, stores and processes quantum information, following the laws of quantum mechanics. The main characteristics of quantum computers include high operating speed, strong information processing capabilities, and a wide range of applications. Compared to conventional computers, the greater the amount of information processed, the more advantageous it is for quantum computers to perform calculations, and the more accurately the calculations can be ensured.

[0003] Superconducting quantum processors composed of microwave-controlled qubit arrays represent the forefront of contemporary digital quantum computing, analog quantum simulation, and modeling. Microwave-controlled qubits enable controllable, high-fidelity single-qubit gates. A key requirement for quantum computing is precise microwave control applied to the drive lines of the qubits, allowing individual control over each qubit. However, microwave crosstalk is a major factor hindering the development of scalable quantum computing. Microwave crosstalk is defined as follows: although the microwave signal applied to a specific drive line is designed to control only one qubit, crosstalk propagation of this signal to other qubits significantly reduces the precision of the qubits executing quantum logic gates.

[0004] It is necessary to accurately determine the crosstalk effect of microwave signals applied to the driving lines of other qubits on the driving lines of each qubit in order to compensate or calibrate.

[0005] It should be noted that the information disclosed in the background section of this application is intended only to enhance the understanding of the general background of this application, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this application is to provide a method and storage medium for determining the crosstalk coefficient of a qubit driving line, which can solve the problem of microwave crosstalk between qubits in the prior art. It can determine the actual microwave signal parameters transmitted on the qubit driving line without experimentation, which is convenient for compensation and calibration.

[0007] To solve the above technical problems, the technical solution of this application is as follows:

[0008] The first aspect of this application proposes a method for determining the crosstalk coefficient of a qubit driving line, comprising:

[0009] Several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset for the target qubit; wherein, the amplitude crosstalk coefficients and the phase crosstalk coefficients are used to characterize the amplitude crosstalk effect and phase crosstalk effect of the initial microwave signal applied to the driving line of other qubits on the quantum processor on the driving line of the target qubit.

[0010] Based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients, several target operating frequencies of the target qubit are determined;

[0011] The Rabi oscillation experiment was performed on the target qubit to obtain the measurement operating frequency of the target qubit;

[0012] The amplitude crosstalk coefficient and phase crosstalk coefficient when the target operating frequency is the same as the measured operating frequency are determined as the crosstalk coefficient of the target qubit.

[0013] Optionally, the method described above may involve determining several target operating frequencies of the target qubit based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the qubit's operating frequency and the amplitude crosstalk coefficients and phase crosstalk coefficients, including:

[0014] Obtain the capacitance parameters of the target qubit;

[0015] Obtain the initial amplitude and initial phase of the initial microwave signal applied to the driving line of the target qubit;

[0016] Based on the capacitance parameters, the initial amplitude, the initial phase, several sets of amplitude crosstalk coefficients and phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients, several target operating frequencies of the target qubit are determined.

[0017] As described above, optionally, the correspondence is as follows:

[0018]

[0019] Among them, the For operating frequency, It is the capacitance parameter between the qubit and the driving line. C j It is the capacitance parameter in a qubit. is Planck's constant. It represents the characteristic magnitude of the charge zero-point fluctuation of a qubit; n is the total number of qubits and driving lines. It is the constant voltage of the signal on the driving line of the qubit, A iIt is the initial amplitude r of the square envelope function of the microwave signal applied on the drive line. i→j R is the amplitude crosstalk coefficient of the crosstalk signal from the driving line of the i-th qubit to the driving line of the j-th qubit. x→j It is the amplitude crosstalk coefficient of the crosstalk signal from the driving line of the z-th qubit to the driving line of the j-th qubit. It is the initial phase of the microwave signal applied to the driving line of the i-th qubit. It is the initial phase of the microwave signal applied to the driving line of the z-th qubit, φ. i→j φ is the phase crosstalk coefficient of the crosstalk signal from the driving line of the i-th qubit to the driving line of the j-th qubit. z→j It is the phase crosstalk coefficient of the crosstalk signal from the driving line of the z-th qubit to the driving line of the j-th qubit.

[0020] Optionally, the method described above involves performing a Rabi oscillation experiment on the target qubit to obtain the measurement operating frequency of the target qubit, including:

[0021] The quantum state of the target qubit is modulated to the ground state;

[0022] An initial microwave signal is applied to the driving lines of all other qubits;

[0023] Obtain the curve of the quantum state of the target qubit changing with the initial microwave signal;

[0024] The measurement operating frequency of the target qubit is determined based on the oscillation frequency of the change curve.

[0025] Optionally, when the target operating frequency differs from the measured operating frequency, the method further includes:

[0026] Obtain the difference between the target operating frequency and the measured operating frequency corresponding to each set of amplitude crosstalk coefficients and phase crosstalk coefficients;

[0027] Based on the difference, a gradient descent optimization algorithm is used to optimize the amplitude crosstalk coefficient and the phase crosstalk coefficient. Then, the steps of determining several target operating frequencies of the target qubit based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the qubit's operating frequency and the amplitude crosstalk coefficients and the phase crosstalk coefficients are returned until the target operating frequency is the same as the measured operating frequency.

[0028] Optionally, the method described above may further include:

[0029] During optimization, the amplitude crosstalk coefficient, the phase crosstalk coefficient, and the corresponding target operating frequency of each group are obtained as the parameter set of the current target qubit.

[0030] Select another qubit on the quantum processor as the next target qubit;

[0031] Based on the parameter set, several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset for the next target qubit.

[0032] A second aspect of this application provides a method for determining the crosstalk coefficient of a qubit driving line, comprising:

[0033] Several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset for the target qubit; wherein, the amplitude crosstalk coefficients and the phase crosstalk coefficients are used to characterize the amplitude crosstalk effect and phase crosstalk effect of the initial microwave signal applied to the driving line of other qubits on the quantum processor on the driving line of the target qubit.

[0034] Based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients, several target operating frequencies of the target qubit are determined;

[0035] A simulation model of the crosstalk coefficient of the qubit driving line is constructed based on the amplitude crosstalk coefficient, the phase crosstalk coefficient, and the corresponding target operating frequency;

[0036] The amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit are determined based on the simulation model and the measurement operating frequency obtained by measuring the target qubit.

[0037] Optionally, the method described above involves determining the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit based on the simulation model and the measurement operating frequency obtained by measuring the target qubit, including:

[0038] The Rabi oscillation experiment is performed on the target qubit to obtain the measurement operating frequency of the target qubit;

[0039] Input a target operating frequency that is the same as the measured operating frequency into the simulation model;

[0040] The amplitude crosstalk coefficient and phase crosstalk coefficient output by the simulation model are obtained as the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit.

[0041] A third aspect of this application provides a method for determining the crosstalk matrix of a quantum processor, comprising:

[0042] One qubit on the quantum processor is selected sequentially as the target qubit;

[0043] The crosstalk coefficient of the target qubit is determined by the method described in any of the first aspects above or by the method described in any of the second aspects above, until the crosstalk coefficients of all qubits on the quantum processor are obtained;

[0044] The crosstalk matrix of the quantum processor is determined based on the crosstalk coefficients of all qubits.

[0045] A fourth aspect of this application provides a readable storage medium having a computer program stored thereon. When executed by a processor, the computer program can implement the method for determining the crosstalk coefficient of a qubit driving line as described in any of the first or second aspects above to determine the crosstalk coefficient on the driving line of a target qubit, or execute the method for determining the crosstalk matrix of a quantum processor as described in the third aspect above to determine the crosstalk matrix of the quantum processor.

[0046] Compared with the prior art, this application has the following beneficial effects:

[0047] This application first presets several sets of amplitude crosstalk coefficients and phase crosstalk coefficients for the target qubit. Based on the correspondence between the target operating frequency and these coefficients, it determines the target operating frequency for each preset set of coefficients. Then, it obtains the measured operating frequency of the target qubit through a Rabi oscillation experiment and compares it with the target operating frequency. The crosstalk coefficients at the target operating frequency and the measured operating frequency are then identified as the crosstalk coefficients of the target qubit. By calculating the several target operating frequencies through this application and comparing them with the results of the Rabi oscillation experiment, it is possible to determine the crosstalk influence of microwave signals applied to the driving lines of other qubits on the target qubit's driving line, allowing for calibration or compensation. The operation process is simple, time-saving, and labor-saving.

[0048] The method for determining the crosstalk coefficient of qubits, the method for determining the crosstalk matrix of a quantum processor, and the readable storage medium proposed in this application belong to the same concept as the method for determining the crosstalk coefficient of the qubit driving line, and therefore have the same beneficial effects, which will not be elaborated here. Attached Figure Description

[0049] Figure 1 This is a schematic diagram illustrating the effect of adjacent qubit crosstalk as an example of an embodiment of this application;

[0050] Figure 2 This is a flowchart illustrating a method for determining the crosstalk coefficient of a qubit driving line according to an embodiment of this application.

[0051] Figure 3 This is a schematic diagram of a process for determining several target operating frequencies of a target qubit according to an embodiment of this application;

[0052] Figure 4 This is a schematic diagram of a process for obtaining the measurement operating frequency of a target qubit according to an embodiment of this application;

[0053] Figure 5 This is a schematic diagram of a process for obtaining the measurement operating frequency of a target qubit when the target operating frequency is different from the measurement operating frequency, according to an embodiment of this application.

[0054] Figure 6 This is a flowchart illustrating a method for determining the crosstalk coefficient of a driving line for multiple target qubits on a quantum processor, as proposed in an embodiment of this application.

[0055] Figure 7 This is a flowchart illustrating another method for determining the crosstalk coefficient of a qubit driving line proposed in an embodiment of this application.

[0056] Figure 8 This is a flowchart illustrating a method for determining the crosstalk coefficient of a qubit driving line based on a simulation model, as proposed in an embodiment of this application.

[0057] Figure 9 This is a flowchart illustrating a method for determining the crosstalk matrix of a quantum processor according to an embodiment of this application. Detailed Implementation

[0058] The specific embodiments of this application will be described in more detail below with reference to the schematic diagrams. The advantages and features of this application will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this application.

[0059] In the description of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0061] A quantum processor integrates multiple qubits, each with a corresponding driving line. Driving a qubit requires applying a driving signal (such as a microwave signal) to that driving line. Ideally, the driving signal applied to each qubit's driving line should only drive that specific qubit. However, in practical applications, the driving signal applied to each qubit's driving line can not only drive that qubit but also drive adjacent or nearby qubits through spatial radiation, affecting the driving of other qubits (crosstalk). Figure 1 The diagram shows the driving accuracy of two adjacent qubits. Crosstalk directly affects the driving accuracy of each qubit, and thus the computational accuracy of the qubits performing quantum computing tasks.

[0062] Figure 1 The diagram illustrates two qubits (Qubit1 and Qubit2), each with corresponding drive lines (Drive Line1 and Drive Line2). The drive lines are frequency drive lines for the qubits, and the microwave signals applied to these lines drive the qubits' operating frequency. The operating frequency of a qubit when performing an operation is called its operating point. When performing quantum gate operations, the operating frequency directly affects the precision of the qubit's operation. When microwave signals are applied to the frequency drive lines of other qubits, they directly affect the frequency of the current qubit, causing a shift in its operating frequency and thus reducing the precision of its quantum gate operations. Therefore, it is necessary to determine the crosstalk effects of microwave signals applied to the drive lines of other qubits on the drive lines of each qubit in order to compensate for or calibrate these effects.

[0063] like Figure 2 As shown in the figure, this application provides a method for determining the crosstalk coefficient of a qubit driving line, including the following steps.

[0064] Step S10: Preset several sets of amplitude crosstalk coefficients and phase crosstalk coefficients for the target qubit; wherein, the amplitude crosstalk coefficients and phase crosstalk coefficients are used to characterize the amplitude crosstalk effect and phase crosstalk effect of the initial microwave signal applied to the driving line of other qubits on the quantum processor on the driving line of the target qubit.

[0065] Specifically, in this embodiment, the target qubit is a qubit on the quantum processor. When it is necessary to determine the crosstalk coefficient of the driving line of this qubit, the qubit is defined as the target qubit. The driving line of each target qubit is affected by the amplitude crosstalk and phase crosstalk of the initial microwave signal applied to the driving lines of other qubits. The amplitude crosstalk coefficient and the phase crosstalk coefficient can be expressed as:

[0066] R i =[r 0→i r 1→i , ..., rn→i ]

[0067]

[0068] Among them, R i This represents the amplitude crosstalk coefficient of the i-th target qubit. R represents the phase crosstalk coefficient of the i-th target qubit; 0→i r represents the amplitude crosstalk between the 0th qubit and the i-th target qubit. 1→i This represents the amplitude crosstalk between the 1st qubit and the i-th target qubit. This represents the phase crosstalk between the 0th qubit and the i-th target qubit. This represents the phase crosstalk between the 1st qubit and the i-th target qubit, and so on up to the n-th qubit. The number n can be represented as the number of qubits on the quantum processor.

[0069] It is conceivable that when the preset amplitude crosstalk coefficient and phase crosstalk coefficient on the target qubit are different, the crosstalk effect on the driving line of the target qubit will also be different, causing the operating frequency of the target qubit to change accordingly.

[0070] In addition, it should be noted that when setting several sets of amplitude crosstalk coefficients and phase crosstalk coefficients, one or two of the amplitude crosstalk coefficients and phase crosstalk coefficients in each set can be changed to obtain several sets of preset parameters.

[0071] Step S20: Determine several target operating frequencies of the target qubit based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the qubit's operating frequency and the amplitude crosstalk coefficients and phase crosstalk coefficients.

[0072] A qubit is a two-level quantum system, which can be understood as an oscillator consisting of an inductor (i.e., a superconducting Josephson junction loop formed by two parallel superconducting Josephson junctions) and a capacitor connected in parallel. Its oscillation frequency can be understood as its operating frequency. The operating frequency of the qubit is adjusted by applying a microwave signal to it, thereby regulating the equivalent inductance of the inductor. In other words, the operating frequency of the qubit corresponds to the applied microwave signal. Furthermore, the operating frequency of the qubit changes when the applied microwave signal is affected by crosstalk. When the applied microwave signal is fixed, the operating frequency of the qubit changes with the crosstalk, meaning there is also a correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficient and the phase crosstalk coefficient. The target operating frequency in this embodiment is the operating frequency after considering the amplitude and phase crosstalk effects of other qubits on the target qubit's driving line, and can be obtained through calculation.

[0073] In this embodiment, the correspondence between the operating frequency and the amplitude crosstalk coefficient and the phase crosstalk coefficient is as follows:

[0074]

[0075] in, For operating frequency, It is the capacitance parameter between the qubit and the driving line. C j It is the capacitance parameter in a qubit. is Planck's constant. It represents the characteristic magnitude of the charge zero-point fluctuation of a qubit; n is the total number of qubits and driving lines. It is the constant voltage of the signal on the driving line of the qubit, A i It is the initial amplitude r of the square envelope function of the microwave signal applied on the drive line. i→j R is the amplitude crosstalk coefficient of the crosstalk signal from the driving line of the i-th qubit to the driving line of the j-th qubit. z→j It is the amplitude crosstalk coefficient of the crosstalk signal from the driving line of the z-th qubit to the driving line of the j-th qubit. It is the initial phase of the microwave signal applied to the driving line of the i-th qubit. It is the initial phase of the microwave signal applied to the driving line of the z-th qubit, φ. i→j φ is the phase crosstalk coefficient of the crosstalk signal from the driving line of the i-th qubit to the driving line of the j-th qubit. z→j It is the phase crosstalk coefficient of the crosstalk signal from the driving line of the z-th qubit to the driving line of the j-th qubit.

[0076] The capacitance parameter of a qubit is determined as a fixed value after the quantum processor is fabricated, and can be obtained through measurement. Furthermore, the aforementioned... A i S z , These are all parameters of the initial microwave signal applied to the driving line of the qubit, which can be set by the signal source device; therefore, according to the above correspondence, the target operating frequency of the target qubit can be determined after each preset of the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit.

[0077] It should be added that the target operating frequency was obtained through calculation and is the expected result of frequency modulation of the target qubit after taking into account the crosstalk effect of the initial microwave signal applied to the driving line of the target qubit being applied to the driving lines of other qubits.

[0078] Step S30: Perform a Rabi oscillation experiment on the target qubit to obtain the measurement operating frequency of the target qubit.

[0079] In the quantum realm, the Rabi oscillation experiment is also known as the Rabi experiment. Specifically, an initial microwave signal is applied to the driving line of the target qubit to regulate its operating frequency. In addition, the operating frequency of the target qubit is also affected by crosstalk. A π-gate signal is applied to the quantum state control line of the target qubit, and then the quantum state change curve of the target qubit is measured. The measured operating frequency of the target qubit is obtained through the quantum state change curve.

[0080] In this step, the measured operating frequency obtained through measurement is the result under the influence of crosstalk; therefore, it can be compared with the target operating frequency determined by calculation in step S20. Furthermore, this experiment only needs to be performed once.

[0081] Step S40: Determine the amplitude crosstalk coefficient and phase crosstalk coefficient when the target operating frequency is the same as the measurement operating frequency as the crosstalk coefficient of the target qubit.

[0082] Specifically, the target operating frequency of the qubit obtained in steps S10-S20 is under the influence of crosstalk, and the measurement operating frequency obtained in step S30 is also under the influence of crosstalk. Therefore, when comparing the target operating frequency and the measurement operating frequency, the amplitude crosstalk coefficient and phase crosstalk coefficient preset in step S10 can be determined as the crosstalk coefficient of the target qubit.

[0083] This application first presets several sets of amplitude crosstalk coefficients and phase crosstalk coefficients for the target qubit. Based on the correspondence between the target operating frequency and these coefficients, it determines the target operating frequency for each preset set of coefficients. Then, it obtains the measured operating frequency of the target qubit through a Rabi oscillation experiment and compares it with the target operating frequency. The crosstalk coefficients at the target operating frequency and the measured operating frequency are then identified as the crosstalk coefficients of the target qubit. By calculating the several target operating frequencies through this application and comparing them with the results of the Rabi oscillation experiment, it is possible to determine the crosstalk influence of microwave signals applied to the driving lines of other qubits on the target qubit's driving line, allowing for calibration or compensation. The operation process is simple, time-saving, and labor-saving.

[0084] like Figure 3 As shown, in this embodiment, several target operating frequencies of the target qubit are determined based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and phase crosstalk coefficients, including the following steps.

[0085] Step S201: Obtain the capacitance parameters of the target qubit.

[0086] Step S202: Obtain the initial amplitude and initial phase of the initial microwave signal applied to the driving line of the target qubit.

[0087] The capacitance parameters in step S101 include the inherent capacitance of the qubit and the coupling capacitance between the qubit and the driving line. These capacitance parameters directly affect the frequency modulation result of the initial microwave signal applied to the driving line of the target qubit. Furthermore, the initial microwave signal is used to adjust the operating frequency of the target qubit, and the initial amplitude and initial phase of the initial microwave signal applied to the driving line of the target qubit also affect the adjustment result of the operating frequency. These parameters are preset in steps S201 and S202 for subsequent steps to determine the target operating frequency of the qubit.

[0088] Step S203: Determine several target operating frequencies of several target qubits based on capacitance parameters, initial amplitude, initial phase, several sets of amplitude crosstalk coefficients and phase crosstalk coefficients, and their corresponding relationships.

[0089] As described in step S20, there is a corresponding relationship between the operating frequency of the qubit and the amplitude crosstalk coefficient and the phase crosstalk coefficient, and these are affected by the capacitance parameter, the initial amplitude, and the initial phase. Once these parameters are preset, the corresponding target operating frequency can be determined according to the correspondence. Furthermore, among these parameters, the capacitance parameter is determined as a fixed value after the quantum processor is fabricated and can be obtained through measurement. The initial amplitude and initial phase are parameters of the initial microwave signal applied to the driving line of the qubit and can be set by the signal source device. Several sets of amplitude crosstalk coefficients and phase crosstalk coefficients can be preset.

[0090] like Figure 4 As shown, the Rabi oscillation experiment is performed on the target qubit to obtain the measurement operating frequency of the target qubit, including the following steps.

[0091] Step S301: Modulate the quantum state of the target qubit to the ground state.

[0092] Step S302: Apply an initial microwave signal to the driving lines of all other qubits.

[0093] Step S303: Obtain the curve of the quantum state of the target qubit changing with the initial microwave signal.

[0094] Step S304: Determine the measurement operating frequency of the target qubit based on the oscillation frequency of the change curve.

[0095] When performing Rabi oscillation experiments on the target qubit, the quantum state of the target qubit is tuned to the ground state, and an initial microwave signal is applied to the driving lines of other qubits to generate crosstalk to the driving lines of the target qubit, causing the operating frequency of the target qubit to change, thereby changing the quantum state of the target qubit and obtaining a change curve. The measured operating frequency of the target qubit can be obtained through the change curve, which is convenient for comparison with the target operating frequency obtained in step S20 above.

[0096] In steps S10-S40 above, several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset, and several target operating frequencies are obtained. Then, the measured operating frequency of the target qubit is obtained through a Rabi oscillation experiment for comparison. If a target operating frequency is the same as the measured operating frequency, the set of amplitude crosstalk coefficients and phase crosstalk coefficients corresponding to this target operating frequency is determined. It is conceivable that there might be a situation where the target operating frequencies for the preset sets of amplitude crosstalk coefficients and phase crosstalk coefficients are all different from the measured operating frequency.

[0097] like Figure 5 As shown, when the target operating frequency is different from the measured operating frequency, the method also includes the following steps.

[0098] Step S50: Obtain the difference between the target operating frequency and the measured operating frequency corresponding to each set of amplitude crosstalk coefficients and phase crosstalk coefficients.

[0099] Step S60: Based on the difference, the gradient descent optimization algorithm is used to optimize the amplitude crosstalk coefficient and the phase crosstalk coefficient, and the steps to determine several target operating frequencies of the target qubit are returned until the target operating frequency is the same as the measured operating frequency.

[0100] In step S10, when several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset, they are generally preset randomly. Therefore, in subsequent steps S20-S40, when comparing the measured working frequency with the target working frequency, there may be a situation where the target working frequencies of the preset several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are not the same as the measured working frequency.

[0101] In this embodiment, after performing the Rabi oscillation experiment to obtain the measurement operating frequency of the target qubit, the difference between the target operating frequency and the measurement operating frequency corresponding to the amplitude crosstalk coefficient and phase crosstalk coefficient of each group can be obtained. Then, the amplitude crosstalk coefficient and phase crosstalk coefficient are optimized using the gradient descent algorithm based on the difference, and the process returns to step S20 so that the target operating frequency corresponding to the optimized amplitude crosstalk coefficient and phase crosstalk coefficient is closer to the measurement operating frequency.

[0102] Alternatively, the Nelder-Mead optimization algorithm can be used to optimize the amplitude crosstalk coefficient and phase crosstalk coefficient, or other optimization algorithms can be employed, returning to step S20. This allows the target operating frequency corresponding to the preset amplitude crosstalk coefficient and phase crosstalk coefficient to be closer to the measurement operating frequency, until they are equal. By employing optimization algorithms, the efficiency of this method in determining the crosstalk coefficient can be improved, and the crosstalk coefficient of the target qubit can be determined more quickly.

[0103] A quantum processor integrates multiple qubits, and the crosstalk coefficient of the driving line for each qubit needs to be determined individually. For example... Figure 6 As shown, this embodiment provides a method for determining the crosstalk coefficient of the driving lines of multiple target qubits on a quantum processor, the method including the following steps.

[0104] Step S70: Obtain the amplitude crosstalk coefficient, phase crosstalk coefficient, and corresponding target operating frequency for each set during optimization, as the parameter set for the current target qubit.

[0105] Step S80: Select another qubit on the quantum processor as the next target qubit.

[0106] Step S90: Based on the parameter set, preset several sets of amplitude crosstalk coefficients and phase crosstalk coefficients for the next target qubit.

[0107] Referring to the description in step S50 above, when setting several sets of amplitude crosstalk coefficients and phase crosstalk coefficients, they are generally randomly preset. In subsequent steps S20-S40, when comparing the measured working frequency with the target working frequency, there may be a situation where the target working frequencies of the preset several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are all different from the measured working frequency.

[0108] In this embodiment, when performing steps S10-S60 for a target qubit, each set of amplitude crosstalk coefficients, phase crosstalk coefficients, and corresponding target operating frequencies during optimization are used as the parameter set for that target qubit. The parameter set can intuitively show the correspondence between the amplitude crosstalk coefficients, phase crosstalk coefficients, and corresponding target operating frequencies. When it is necessary to perform steps S10-S60 to determine the crosstalk coefficient of another qubit on the quantum processor as the next target qubit, the parameter set of the target qubit can be referenced. This makes it easier to ensure that when several sets of amplitude crosstalk coefficients and phase crosstalk coefficients are preset, the target operating frequencies corresponding to the preset amplitude crosstalk coefficients and phase crosstalk coefficients are closer to or equal to the measurement operating frequency, thereby improving the efficiency of the method for determining the crosstalk coefficient in this embodiment and determining the crosstalk coefficient of the qubit more quickly.

[0109] like Figure 7As shown, based on the same application concept, this application embodiment also provides another method for determining the crosstalk coefficient of a qubit driving line, including the following steps.

[0110] Step S11: Preset several sets of amplitude crosstalk coefficients and phase crosstalk coefficients for the target qubit; wherein, the amplitude crosstalk coefficients and phase crosstalk coefficients are used to characterize the amplitude crosstalk effect and phase crosstalk effect of the initial microwave signal applied to the driving line of other qubits on the quantum processor on the driving line of the target qubit.

[0111] Step S21: Determine several target operating frequencies of the target qubit based on several sets of amplitude crosstalk coefficients, phase crosstalk coefficients, and the correspondence between the qubit's operating frequency and the amplitude crosstalk coefficients and phase crosstalk coefficients.

[0112] Step S31: Construct a simulation model of the crosstalk coefficient of the qubit driving line based on the amplitude crosstalk coefficient, the phase crosstalk coefficient, and the corresponding target operating frequency.

[0113] Step S41: Determine the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit based on the simulation model and the measurement operating frequency obtained by measuring the target qubit.

[0114] In this embodiment, the process of first obtaining the amplitude crosstalk coefficient and phase crosstalk coefficient, and then determining the corresponding target operating frequency based on the correspondence, can be performed using a training method. A simulation model of the crosstalk coefficient of the qubit driving line is then constructed based on the training results. On one hand, the input data of this simulation model can be the amplitude crosstalk coefficient and the phase crosstalk coefficient, with the output being the target operating frequency; on the other hand, the input data of this simulation model can be the target operating frequency, with the output data being the amplitude crosstalk coefficient and the phase crosstalk coefficient.

[0115] The target qubit is then measured to obtain the measurement operating frequency. The measurement operating frequency is then used as the input data of the simulation model to obtain the amplitude crosstalk coefficient and phase crosstalk coefficient output by the simulation model as the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit.

[0116] The simulation model of the crosstalk coefficient of the qubit driving line obtained by this step can quickly obtain the output amplitude crosstalk coefficient and phase crosstalk coefficient based on the input target operating frequency, which is convenient for comparison with the measurement operating frequency obtained in the aforementioned step S30, thereby improving the efficiency of the method for determining the crosstalk coefficient of the qubit driving line.

[0117] like Figure 8 As shown, the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit are determined based on the simulation model and the measurement operating frequency obtained by measuring the target qubit, including the following steps.

[0118] Step S511: Perform a Rabi oscillation experiment on the target qubit to obtain the measurement operating frequency of the target qubit.

[0119] Step S512: Input the target operating frequency, which is the same as the measured operating frequency, into the simulation model.

[0120] Step S513: Obtain the amplitude crosstalk coefficient and phase crosstalk coefficient output by the simulation model as the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit.

[0121] After training and constructing a simulation model for the crosstalk coefficient, a Rabi oscillation experiment is performed on the target qubit to obtain the measured operating frequency. Then, the value of the measured operating frequency is used as the target operating frequency and input into the simulation model to obtain the corresponding amplitude crosstalk coefficient and phase crosstalk coefficient. These are then used as the amplitude crosstalk coefficient and phase crosstalk coefficient of the target qubit, which greatly improves the efficiency of the method for determining the crosstalk coefficient of the driving line of the qubit.

[0122] like Figure 9 As shown, based on the same application concept, this application embodiment also provides a method for determining the crosstalk matrix of a quantum processor, characterized by including the following steps.

[0123] Step S13: Select one qubit on the quantum processor as the target qubit in sequence.

[0124] Step S23: Determine the crosstalk coefficient of the target qubit using any of the methods described above for determining the crosstalk coefficient of the qubit driving line, until the crosstalk coefficients of all qubits on the quantum processor are obtained.

[0125] Step S33: Determine the crosstalk matrix of the quantum processor based on the crosstalk coefficients of all qubits.

[0126] The aforementioned steps can obtain the crosstalk coefficient of the driving line of a single target qubit. For a quantum processor, the number of qubits integrated on it is very large. The crosstalk coefficient of the driving line of each qubit can be obtained by the aforementioned steps S10-S40. Then, the crosstalk coefficients of the driving lines of all qubits are combined into a crosstalk matrix to represent the crosstalk coefficients of the driving lines of all qubits on the quantum processor.

[0127] During the process of sequentially selecting a qubit on the quantum processor as the target qubit and executing steps S10-S40, the first target qubit can execute the above steps S10-S40 to obtain the crosstalk coefficient. The second target qubit and other subsequent target qubits can first execute steps S70-S80 to obtain the parameter set of the first target qubit, and then repeat steps S10-S40 according to the parameter set, which facilitates the rapid determination of the crosstalk coefficient of each qubit.

[0128] Furthermore, if the measured operating frequency deviates significantly from the target operating frequency during the execution of steps S10-S40, steps S50-S60 can be executed to quickly determine the amplitude crosstalk coefficient and phase crosstalk coefficient, and update the parameter set in step S70.

[0129] Based on the same concept, embodiments of this application also provide a readable storage medium storing a computer program thereon. When executed by a processor, the computer program can implement any of the methods described above for determining the crosstalk coefficient of a qubit driving line to determine the crosstalk coefficient on the driving line of a target qubit, or execute the method described above for determining the crosstalk matrix of a quantum processor to determine the crosstalk matrix of the quantum processor.

[0130] A readable storage medium can be a tangible device capable of holding and storing instructions for use by an instruction execution device, such as, but not limited to, electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination thereof. The computer programs described herein can be downloaded from the readable storage medium to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. Networks can include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. Each computing / processing device's network adapter card or network interface receives the computer program from the network and forwards it for storage on a readable storage medium within the respective computing / processing device. The computer program used to perform the operations of this application can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as "C" or similar languages. The computer program can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuits, such as programmable logic circuits, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), are personalized by utilizing state information from a computer program. These electronic circuits can execute computer-readable program instructions to implement various aspects of this application.

[0131] Various aspects of this application are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of this application. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by a computer program. These computer programs can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus to produce a machine such that, when executed by the processor of the computer or other programmable data processing apparatus, they create means for implementing the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams. These computer programs can also be stored in a readable storage medium that causes a computer, programmable data processing apparatus, and / or other device to operate in a particular manner; thus, the readable storage medium storing the computer program includes an article of manufacture comprising instructions for implementing various aspects of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams.

[0132] A computer program may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the computer program executing on the computer, other programmable data processing apparatus, or other device to perform the functions / actions specified in one or more boxes of a flowchart and / or block diagram.

[0133] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0134] The above are merely preferred embodiments of this application and do not constitute any limitation on this application. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in this application without departing from the scope of the technical solutions of this application shall still fall within the protection scope of this application.

Claims

1. A method of determining a crosstalk coefficient of a drive line of a qubit, characterized in that, The method comprises: a plurality of sets of amplitude crosstalk coefficients and phase crosstalk coefficients of a preset target qubit; wherein the amplitude crosstalk coefficients and the phase crosstalk coefficients are used to represent the amplitude crosstalk effect and the phase crosstalk effect of an initial microwave signal applied on the drive line of other qubits on the quantum processor on the drive line of the target qubit; determining a plurality of target operating frequencies of the target qubit according to the plurality of sets of the amplitude crosstalk coefficients, the phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients; performing a Rabi oscillation experiment on the target qubit to obtain a measured operating frequency of the target qubit; determining the amplitude crosstalk coefficient and the phase crosstalk coefficient that are the same as the measured operating frequency as the crosstalk coefficient of the target qubit.

2. The method of claim 1, wherein, The method of determining a plurality of target operating frequencies of the target qubit according to the plurality of sets of the amplitude crosstalk coefficients, the phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients comprises: obtaining the capacitance parameter of the target qubit; obtaining the initial amplitude and the initial phase of the initial microwave signal applied on the drive line of the target qubit; determining a plurality of target operating frequencies of the target qubit according to the capacitance parameter, the initial amplitude, the initial phase, the plurality of sets of the amplitude crosstalk coefficients and the phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients.

3. The method of claim 1, wherein, The correspondence is: wherein the is the working frequency, is the capacitance parameter between the qubits and the drive lines, C j is the capacitance parameter in the qubits, is the Planck constant, is the characteristic order of magnitude of the charge zero-point fluctuation of the qubits; n is the total number of qubits and drive lines, is the constant voltage of the signal on the drive line of the qubits, A i is the initial amplitude of the square envelope function of the microwave signal applied on the drive line, r i→j is the amplitude crosstalk coefficient of the crosstalk signal from the drive line of the i-th qubit to the drive line of the j-th qubit, r z→j is the amplitude crosstalk coefficient of the crosstalk signal from the drive line of the z-th qubit to the drive line of the j-th qubit, is the initial phase of the microwave signal applied on the drive line of the i-th qubit, is the initial phase of the microwave signal applied on the drive line of the z-th qubit, φ i→j is the phase crosstalk coefficient of the crosstalk signal from the drive line of the i-th qubit to the drive line of the j-th qubit, φ z→j is the phase crosstalk coefficient of the crosstalk signal from the drive line of the z-th qubit to the drive line of the j-th qubit.

4. The method of claim 1, wherein, The method of performing a Rabi oscillation experiment on the target qubit to obtain a measured operating frequency of the target qubit comprises: controlling the quantum state of the target qubit to the ground state; applying an initial microwave signal on the drive line of other qubits; obtaining the change curve of the quantum state of the target qubit with the initial microwave signal; determining the measured operating frequency of the target qubit according to the oscillation frequency of the change curve.

5. The method of claim 1, wherein, When the target operating frequency is different from the measured operating frequency, the method further comprises: obtaining the difference between the target operating frequency and the measured operating frequency corresponding to each set of the amplitude crosstalk coefficients and the phase crosstalk coefficients; optimizing the amplitude crosstalk coefficients and the phase crosstalk coefficients according to the difference by using a gradient descent optimization algorithm, and returning to the step of determining a plurality of target operating frequencies of the target qubit according to the plurality of sets of the amplitude crosstalk coefficients, the phase crosstalk coefficients, and the correspondence between the operating frequency of the qubit and the amplitude crosstalk coefficients and the phase crosstalk coefficients, until the target operating frequency is the same as the measured operating frequency.

6. The method of claim 5, wherein, The method further comprises: obtaining each set of the amplitude crosstalk coefficients, the phase crosstalk coefficients, and the corresponding target operating frequency as the parameter set of the current target qubit during optimization; selecting other qubits on the quantum processor as the next target qubit; presetting a plurality of sets of amplitude crosstalk coefficients and phase crosstalk coefficients of the next target qubit according to the parameter set.

7. A method of determining a crosstalk coefficient of a drive line of a qubit, characterized in that, The method comprises: a plurality of sets of amplitude crosstalk coefficients and phase crosstalk coefficients of a preset target qubit; wherein the amplitude crosstalk coefficients and the phase crosstalk coefficients are used to represent amplitude crosstalk effects and phase crosstalk effects of an initial microwave signal applied on a driving line of other qubits on a driving line of the target qubit; determining a plurality of target operating frequencies of the target qubit according to the plurality of sets of the amplitude crosstalk coefficients, the phase crosstalk coefficients, and a corresponding relationship between operating frequencies of the qubits and the amplitude crosstalk coefficients and the phase crosstalk coefficients; constructing a simulation model of crosstalk coefficients of a qubit driving line according to the amplitude crosstalk coefficients, the phase crosstalk coefficients, and the corresponding target operating frequencies; determining amplitude crosstalk coefficients and phase crosstalk coefficients of the target qubit according to the simulation model and a measured operating frequency obtained by measuring the target qubit.

8. The method of claim 7, wherein, determining amplitude crosstalk coefficients and phase crosstalk coefficients of the target qubit according to the simulation model and a measured operating frequency obtained by measuring the target qubit, comprising: performing a Rabi oscillation experiment on the target qubit to obtain a measured operating frequency of the target qubit; inputting a target operating frequency with the same frequency as the measured operating frequency to the simulation model; obtaining amplitude crosstalk coefficients and phase crosstalk coefficients output by the simulation model as the amplitude crosstalk coefficients and the phase crosstalk coefficients of the target qubit.

9. A method of determining a crosstalk matrix of a quantum processor, characterized in that, comprising: selecting a qubit on the quantum processor as a target qubit in turn; determining crosstalk coefficients of the target qubit by using the method of any one of claims 1-6 or the method of any one of claims 7-8 until crosstalk coefficients of all qubits on the quantum processor are obtained; determining a crosstalk matrix of the quantum processor according to the crosstalk coefficients of all qubits.

10. A readable storage medium, having stored thereon a computer program, characterized in that, The computer program is executed by a processor to implement the method for determining crosstalk coefficients of a qubit driving line of any one of claims 1-6 or any one of claims 7-8 to determine crosstalk coefficients on a driving line of a target qubit, or to implement the method for determining a crosstalk matrix of a quantum processor of claim 9 to determine a crosstalk matrix of the quantum processor.

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