Verification method of crosstalk coefficient of quantum bit driving line and storage medium

Abstract

The invention discloses a verification method of a crosstalk coefficient of a quantum bit driving line and a storage medium, belongs to the technical field of quantum computing, and is used for verifying the crosstalk coefficient representing the crosstalk influence of an initial microwave signal applied to driving lines of other quantum bits on a quantum processor on a driving line of a target quantum bit. The method comprises the following steps: traversing amplitude parameters and phase parameters of initial microwave signals applied to driving lines of other quantum bits in a preset range, and repeatedly executing a Labian oscillation experiment on a target quantum bit to obtain a plurality of corresponding measurement working frequencies; according to the crosstalk coefficient of the target quantum bit, the working frequency of the quantum bit and the corresponding relation between the crosstalk coefficient and the amplitude parameter and the phase parameter of the initial microwave signal, obtaining the target working frequency of each traversal; and verifying the crosstalk coefficient of the driving line of the target quantum bit according to the convergence degree of the difference between the measurement working frequency obtained by each traversal and the target working frequency. The verification result is accurate, and the process is simple.

Description

Technical Field

[0001] This application relates to the field of quantum computing technology, and in particular to a method for verifying the crosstalk coefficient of a qubit driving line and a storage medium thereon. 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 perform compensation or calibration. The accuracy of the determined crosstalk effect also directly affects the subsequent compensation or calibration work.

[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 verifying the crosstalk coefficient of a qubit driving line, which solves the problem of inaccurate crosstalk determination in the prior art and can verify the accuracy of crosstalk.

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

[0008] The first aspect of this application provides a method for verifying the crosstalk coefficient of a qubit driving line, used to verify the crosstalk coefficient characterizing the influence of an initial microwave signal applied to the driving line of another qubit on a quantum processor on the crosstalk of the target qubit driving line, the method comprising:

[0009] The amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits within a preset range are obtained, and the Rabi oscillation experiment is repeatedly performed on the target qubit to obtain several corresponding measurement operating frequencies.

[0010] The target operating frequency for each traversal is obtained based on the correspondence between the crosstalk coefficient of the target qubit, the operating frequency of the qubit and the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal.

[0011] The crosstalk coefficient of the driving line of the target qubit is verified based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal.

[0012] Optionally, after performing Rabi oscillation experiments on the target qubit to obtain several corresponding measurement operating frequencies, the method further includes: (1) traversing the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits within a preset range, and (2) repeatedly performing Rabi oscillation experiments on the target qubit.

[0013] The verification set of the target qubit is determined based on the traversal results; wherein the verification set includes the amplitude and phase of the initial microwave signal applied to the driving line of other qubits, and the measurement operating frequency obtained by performing measurements on the target qubit.

[0014] Optionally, after obtaining the target operating frequency for each traversal based on the crosstalk coefficient to be verified of the target qubit, the operating frequency of the qubit, and the correspondence between the crosstalk coefficient and the amplitude and phase parameters of the initial microwave signal, the method further includes:

[0015] A training set is determined for the target qubit; wherein the training set includes the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits, and the target operating frequency of the target qubit.

[0016] Optionally, the method described above may be used to verify the crosstalk coefficient of the driving line of the target qubit based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal, including:

[0017] Select the target group amplitude parameters, phase parameters, and corresponding measurement operating frequencies from the verification set;

[0018] Select target operating frequencies from the training set that correspond to the same amplitude and phase parameters as those in the validation set;

[0019] The convergence of the difference between the target group's measurement operating frequency and the target operating frequency is obtained;

[0020] The crosstalk coefficient of the driving line of the target qubit is verified based on the convergence.

[0021] Optionally, the method described above may include verifying the crosstalk coefficient of the driving line of the target qubit based on the convergence, including:

[0022] The crosstalk coefficient of the driving line of the target qubit is verified as qualified when the convergence is less than the first preset threshold.

[0023] Optionally, before obtaining the target operating frequency for each traversal based on the crosstalk coefficient to be verified of the target qubit, the operating frequency of the qubit, and the correspondence between the crosstalk coefficient and the amplitude and phase parameters of the initial microwave signal, the method further includes:

[0024] 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.

[0025] 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;

[0026] The Rabi oscillation experiment was performed on the target qubit to obtain the measurement operating frequency of the target qubit;

[0027] 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.

[0028] Optionally, when the crosstalk coefficient verification of the driving line of the target qubit fails, the method further includes:

[0029] The amplitude crosstalk coefficient and phase crosstalk coefficient of the difference between the target operating frequency and the measured operating frequency at a second preset threshold are determined as the crosstalk coefficient of the target qubit;

[0030] It returns the steps of obtaining the target operating frequency for each traversal based on the crosstalk coefficient of the target qubit, the operating frequency of the qubit, the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal.

[0031] As described above, optionally, the correspondence is as follows:

[0032]

[0033] 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. Let be 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 r is the amplitude parameter 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 phase parameter of the microwave signal applied to the driving line of the i-th qubit. φ is the phase parameter of the microwave signal applied to the driving line of the z-th qubit. 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.

[0034] A second aspect of this application provides a quantum computer, including a quantum processor and a signal source device for providing initial microwave signals to drive lines of qubits on the quantum processor; the crosstalk coefficient of the drive lines of the qubits is verified using a crosstalk coefficient verification method for qubit drive lines as described in any of the preceding claims.

[0035] A third aspect of this application provides a readable storage medium having a computer program stored thereon, which, when executed by a processor, enables the verification method described in any of the preceding claims to verify the crosstalk coefficient of a qubit driving line.

[0036] Compared with the prior art, this application has the following beneficial effects:

[0037] This application obtains the measured operating frequency by traversing the amplitude and phase parameters of the initial microwave signal applied by the driving lines of other qubits. During the traversal, a Rabi oscillation experiment is performed for each parameter to obtain the measured operating frequency. The target operating frequency is calculated based on the crosstalk coefficient to be verified and the corresponding relationship. The measured operating frequency and the target operating frequency obtained in each traversal are compared, and the convergence of the two frequency differences is used to verify whether the crosstalk coefficient is qualified. The use of multiple traversal comparisons makes the verification results of the crosstalk coefficient more accurate, and the process is simple, time-saving and labor-saving.

[0038] The quantum computer and readable storage medium proposed in this application, as well as the method for verifying the crosstalk coefficient of the qubit driving line, belong to the same concept and therefore have the same beneficial effects, which will not be elaborated here. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating the effect of adjacent qubit crosstalk as an example of an embodiment of this application;

[0040] Figure 2 This is a flowchart illustrating a method for verifying the crosstalk coefficient of a qubit driving line according to an embodiment of this application.

[0041] Figure 3 This is a schematic diagram of a process for verifying the crosstalk coefficient of the driving line of a target qubit based on convergence, as proposed in an embodiment of this application.

[0042] Figure 4 This is a schematic diagram of a process for determining the crosstalk coefficient to be verified according to an embodiment of this application;

[0043] Figure 5 This is a schematic diagram of a process when the crosstalk coefficient verification of the driving line of the target qubit fails, as proposed in an embodiment of this application. Detailed Implementation

[0044] 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.

[0045] 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 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.

[0046] 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.

[0047] 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.

[0048] 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 on the drive lines of each qubit caused by microwave signals applied to the drive lines of other qubits for compensation or calibration. The accuracy of the determined crosstalk effects directly affects subsequent compensation or calibration work, therefore, the determined crosstalk effects need to be verified.

[0049] like Figure 2 As shown, this application provides a method for verifying the crosstalk coefficient of a qubit driving line, which is used to verify the crosstalk coefficient that characterizes the effect of an initial microwave signal applied to the driving line of another qubit on the target qubit on the crosstalk of the driving line. The method includes the following steps.

[0050] Step S10: Traverse the amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits within a preset range, and repeatedly perform Rabi oscillation experiments on the target qubit to obtain several corresponding measurement operating frequencies.

[0051] In this embodiment, the Rabi oscillation experiment is used to measure the operating frequency of the qubit. Specifically, the Rabi oscillation experiment, also known as the Rabi experiment, involves applying an initial microwave signal 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.

[0052] In Rabi oscillation experiments targeting a target qubit, the quantum state of the target qubit is modulated to its ground state, and an initial microwave signal is applied to the driving lines of other qubits to induce crosstalk, causing a change in the operating frequency of the target qubit. The initial microwave signal has amplitude and phase parameters; as the amplitude and phase parameters of the initial microwave signals applied to the driving lines of other qubits change, their crosstalk effect on the target qubit also changes.

[0053] In practical implementation, multiple values ​​can be set for the amplitude and phase parameters of the initial microwave signal, for example, multiple values ​​can be set within a preset range, and then these values ​​are iterated one by one. Specifically, iterating for the amplitude and phase parameters means taking values ​​for the amplitude and phase parameters of the initial microwave signal within the preset range, and then applying the initial microwave signal with these values ​​to the driving lines of other qubits to generate crosstalk to the target qubit, and performing a Rabi oscillation experiment on the target qubit to obtain the corresponding measurement operating frequency; therefore, a measurement operating frequency after crosstalk is obtained during each iteration.

[0054] Step S20: Obtain the target operating frequency for each traversal based on the correspondence between the crosstalk coefficient of the target qubit, the operating frequency of the qubit, the crosstalk coefficient, the amplitude parameters of the initial microwave signal, and the phase parameters.

[0055] 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 can be 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 varies with the crosstalk. That is, the operating frequency of the qubit also corresponds to the amplitude crosstalk coefficient, the phase crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits.

[0056] In this embodiment, the target operating frequency is the operating frequency after considering the influence of amplitude crosstalk and phase crosstalk from other qubits on the driving line of the target qubit. The amplitude crosstalk influence is related to the amplitude crosstalk coefficient and the amplitude parameter, and the phase crosstalk influence is related to the phase crosstalk coefficient and the phase parameter. The operating frequency of the target qubit after the influence can be obtained by calculation. Among them, the amplitude crosstalk coefficient and the phase crosstalk coefficient are determined crosstalk coefficients, which need to be verified in this embodiment, and are verified through the subsequent step S30.

[0057] Specifically, in step S10, when the amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits change each time, the target operating frequency obtained by calculation also changes as the amplitude and phase parameters change. Therefore, for each traversal, the corresponding target operating frequency is calculated based on the crosstalk coefficient of the target qubit to be verified and the amplitude and phase parameters selected during the traversal.

[0058] Step S30: Verify the crosstalk coefficient of the driving line of the target qubit based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal.

[0059] It is understandable that for each traversal, the measured operating frequency obtained in step S10 is obtained through Rabi oscillation experiment, while the frequency obtained in step S20 is obtained through correspondence calculation; the correspondence includes the crosstalk coefficient to be verified, so the accuracy of the crosstalk coefficient can be determined by comparing the measured operating frequency with the target operating frequency.

[0060] Specifically, for each traversal, the difference between the measured operating frequency and the target operating frequency is calculated. Then, for all traversal results, it is determined whether the difference converges. If it converges, it can be determined that the crosstalk coefficient of the driving line of the target qubit is accurate. If it does not converge, it is determined that the crosstalk coefficient of the driving line of the target qubit is inaccurate, thus realizing the verification of the crosstalk coefficient.

[0061] This application obtains the measured operating frequency by traversing the amplitude and phase parameters of the initial microwave signal applied by the driving lines of other qubits. During the traversal, a Rabi oscillation experiment is performed for each parameter to obtain the measured operating frequency. The target operating frequency is calculated based on the crosstalk coefficient to be verified and the corresponding relationship. The measured operating frequency and the target operating frequency obtained in each traversal are compared, and the convergence of the two frequency differences is used to verify whether the crosstalk coefficient is qualified. The use of multiple traversal comparisons makes the verification results of the crosstalk coefficient more accurate, and the process is simple, time-saving and labor-saving.

[0062] In step S10 above, when traversing the amplitude and phase parameters of the initial microwave signal, an experiment is performed each time to obtain the corresponding measurement operating frequency. The amplitude parameters, phase parameters, and measurement operating frequencies are related. Therefore, after traversing the amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits within a preset range, and repeatedly performing Rabi oscillation experiments on the target qubit to obtain several corresponding measurement operating frequencies, the method further includes: determining the verification set of the target qubit based on the traversal results; wherein, the verification set includes the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits, and the measurement operating frequency obtained by performing measurements on the target qubit.

[0063] Construct a validation set based on the experimental results of step S10 above. A in the validation set i The amplitude parameter of the initial microwave signal applied to the driving line of the qubit. f is the phase of the initial microwave signal applied to the driving line of the qubit. mes，i The measurement operating frequency is obtained for performing measurements on the target qubit. In this verification set, the amplitude parameters, phase parameters, and measurement operating frequencies are all represented in vector form, containing the amplitude and phase parameters of the microwave signals applied to the drive lines of all other qubits, along with their corresponding measurement operating frequencies. After this verification set is constructed, it can be used to verify the crosstalk coefficient of the drive line of any qubit on the quantum processor, using it as the target qubit.

[0064] Similarly, the method of calculating and determining the target operating frequency using the correspondence in step S20 can also be adopted using a set approach. Specifically, after obtaining the target operating frequency for each traversal based on the correspondence between the target qubit's crosstalk coefficient to be verified, the qubit's operating frequency and the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal, the method further includes: determining a training set for the target qubit; wherein, the training set includes the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits, and the target operating frequency of the target qubit.

[0065] A training set is constructed based on the calculation results of step S20 above. A in the training set i The amplitude parameter of the initial microwave signal applied to the driving line of the qubit. f is the phase of the initial microwave signal applied to the driving line of the qubit. lear，i The target operating frequency is calculated through the correspondence. The amplitude parameters, phase parameters, and measured operating frequencies in this training set are all represented in vector form, which includes the amplitude and phase parameters of the microwave signals applied to the driving lines of all other qubits, and the corresponding measured operating frequencies.

[0066] It should be added that the training set mentioned above was calculated based on the crosstalk coefficient to be verified, the amplitude parameters and phase parameters of the initial microwave signal, and their corresponding relationships. These calculations can be obtained through model training.

[0067] For example, first obtain the crosstalk coefficients (amplitude crosstalk coefficient, phase crosstalk coefficient), amplitude parameters, and phase parameters, and determine the corresponding target operating frequency based on the relationship. Then, use a training method to construct a training model of the target operating frequency, amplitude parameters, and phase parameters of the qubit driving line based on the training results. The input data for this training model can be the amplitude parameters and phase parameters, and the output is the target operating frequency.

[0068] Once the validation and training sets are obtained, the crosstalk coefficients of the driving lines of the target qubit can be verified based on the parameters in the validation and training sets. For example... Figure 3 As shown, the crosstalk coefficient of the driving line of the target qubit is verified based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal, including the following steps.

[0069] Step S301: Select the target group amplitude parameters, phase parameters, and corresponding measurement operating frequencies from the verification set.

[0070] Step S302: Select the target operating frequencies from the training set that correspond to the same amplitude and phase parameters as those in the validation set.

[0071] When comparing parameters selected from the validation and training sets, several groups are chosen, and the target operating frequencies corresponding to the same amplitude and phase parameters must be selected. For example, A is selected. 1 =(1, 1.1, 1.2, 1.3, 1.4, 1.5), all selected The amplitude and phase parameters in the validation and training sets are selected to have the same values. Then, the measured operating frequency and the target operating frequency corresponding to each set are compared to achieve accurate verification of the crosstalk coefficient. In this embodiment, the number of target groups is not less than 30 when selecting parameters in the set.

[0072] Step S303: Obtain the convergence of the difference between the target group measurement operating frequency and the target operating frequency.

[0073] Step S304: Verify the crosstalk coefficient of the driving line of the target qubit based on the convergence.

[0074] The validation set is obtained by measuring the operating frequency, which includes the actual crosstalk effect. The training set is obtained by training the target operating frequency under the crosstalk effect using the crosstalk coefficient to be validated. When the difference between the two operating frequencies is very small and converges, it can be determined that the crosstalk coefficient to be validated is accurate.

[0075] Specifically, the crosstalk coefficient of the target qubit's driving line is verified based on the convergence, including determining whether the crosstalk coefficient verification is successful when the convergence is less than a first preset threshold. Ideally, after multiple measurements, the crosstalk coefficient to be verified is most accurate when the measured operating frequency and the target operating frequency are finally equal and the difference is zero. However, considering the influence of factors such as the measurement environment and the accuracy of the signal source, a preset threshold can be set for the maximum value of the difference. When the convergence is less than the first preset threshold, the crosstalk coefficient verification of the target qubit's driving line is deemed successful.

[0076] Before verifying the crosstalk coefficient of a qubit, it is necessary to obtain the crosstalk coefficient first. For example... Figure 4 As shown, this embodiment provides a step for determining the crosstalk coefficient to be verified. Before obtaining the target operating frequency for each traversal based on the crosstalk coefficient to be verified of the target qubit, the correspondence between the qubit's operating frequency and the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal, the method further includes the following steps.

[0077] Step S201: 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.

[0078] 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:

[0079] R i =[r 0→i r 1→i , ..., r n→i ]

[0080]

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Step S202: 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.

[0085] In this embodiment, the correspondence is as follows:

[0086]

[0087] 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. Let be 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, rA 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.

[0088] 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.

[0089] 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.

[0090] Step S203: Perform a Rabi oscillation experiment on the target qubit to obtain the measurement operating frequency of the target qubit.

[0091] The measured operating frequency obtained in this step is the result under the influence of crosstalk; therefore, it can be compared with the target operating frequency determined by calculation in step S202. Furthermore, this experiment only needs to be performed once.

[0092] Step S204: 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.

[0093] Specifically, the target operating frequency of the qubit obtained in steps S201-S202 is under the influence of crosstalk, and the measurement operating frequency obtained in step S203 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 S201 can be determined as the crosstalk coefficient of the target qubit.

[0094] Steps S201-S204 above provide the process of determining the crosstalk coefficient to be verified, and then steps S10-S30 are used to verify the crosstalk coefficient. Figure 5 As shown, when the crosstalk coefficient of the driving line of the target qubit fails the verification, the method further includes the following steps.

[0095] Step S40: Determine the amplitude crosstalk coefficient and phase crosstalk coefficient of the difference between the target operating frequency and the measured operating frequency at the second preset threshold as the crosstalk coefficient of the target qubit.

[0096] Step S50: and return to the step of obtaining the target operating frequency for each traversal based on the correspondence between the crosstalk coefficient of the target qubit, the operating frequency of the qubit and the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal.

[0097] If the crosstalk coefficient obtained in steps S201-204 fails the verification in steps S10-S30, the crosstalk coefficient to be verified needs to be adjusted. In other words, the crosstalk coefficient of the target qubit determined in step S204 based on the fact that the measured working frequency and the target working frequency are equal is not accurate, and the working frequency of the target qubit needs to be adjusted.

[0098] For example, the amplitude crosstalk coefficient and phase crosstalk coefficient at the second preset threshold value of the difference between the target operating frequency and the measured operating frequency are determined as the crosstalk coefficient of the target qubit, and the process returns to step S20 to continue the crosstalk coefficient verification step until the crosstalk coefficient verification is qualified.

[0099] Based on the same concept, this application also provides a quantum computer, including a quantum processor and a signal source device that provides an initial microwave signal for the driving lines of qubits on the quantum processor; the crosstalk coefficient of the driving lines of the qubits is verified using the aforementioned method for verifying the crosstalk coefficient of the driving lines of the qubits.

[0100] Based on the same concept, embodiments of this application also provide a readable storage medium storing a computer program thereon, characterized in that the computer program, when executed by a processor, can implement the above-described verification method to verify the crosstalk coefficient of the qubit driving line.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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 for verifying the crosstalk coefficient of a qubit driving line, characterized in that, The method for verifying the crosstalk coefficient, which characterizes the effect of an initial microwave signal applied to the drive line of other qubits on a quantum processor on the crosstalk of the target qubit, includes: The amplitude and phase parameters of the initial microwave signal applied to the driving lines of other qubits within a preset range are obtained, and the Rabi oscillation experiment is repeatedly performed on the target qubit to obtain several corresponding measurement operating frequencies. The target operating frequency for each traversal is obtained based on the correspondence between the crosstalk coefficient of the target qubit, the operating frequency of the qubit and the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal. The crosstalk coefficient of the driving line of the target qubit is verified based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal.

2. The method as described in claim 1, characterized in that, After measuring the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits within a preset range, and repeatedly performing Rabi oscillation experiments on the target qubit to obtain several corresponding measurement operating frequencies, the method further includes: The verification set of the target qubit is determined based on the traversal results; wherein the verification set includes the amplitude and phase of the initial microwave signal applied to the driving line of other qubits, and the measurement operating frequency obtained by performing measurements on the target qubit.

3. The method as described in claim 2, characterized in that, After obtaining the target operating frequency for each traversal based on the crosstalk coefficient to be verified of the target qubit, the operating frequency of the qubit, and the correspondence between the crosstalk coefficient and the amplitude and phase parameters of the initial microwave signal, the method further includes: A training set is determined for the target qubit; wherein the training set includes the amplitude and phase of the initial microwave signal applied to the driving lines of other qubits, and the target operating frequency of the target qubit.

4. The method as described in claim 3, characterized in that, The crosstalk coefficient of the driving line of the target qubit is verified based on the convergence of the difference between the measured operating frequency and the target operating frequency obtained in each traversal, including: Select the target group amplitude parameters, phase parameters, and corresponding measurement operating frequencies from the verification set; Select target operating frequencies from the training set that correspond to the same amplitude and phase parameters as those in the validation set; The convergence of the difference between the target group's measurement operating frequency and the target operating frequency is obtained; The crosstalk coefficient of the driving line of the target qubit is verified based on the convergence.

5. The method as described in claim 4, characterized in that, Verifying the crosstalk coefficient of the driving line of the target qubit based on the convergence, including: The crosstalk coefficient of the driving line of the target qubit is verified as qualified when the convergence is less than the first preset threshold.

6. The method as described in claim 1, characterized in that, Before obtaining the target operating frequency for each traversal based on the crosstalk coefficient to be verified of the target qubit, the operating frequency of the qubit, and the correspondence between the crosstalk coefficient and the amplitude and phase parameters of the initial microwave signal, the method further includes: 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. 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; The Rabi oscillation experiment was performed on the target qubit to obtain the measurement operating frequency of the target qubit; 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.

7. The method as described in claim 6, characterized in that, When the crosstalk coefficient of the driving line of the target qubit fails the verification, the method further includes: The amplitude crosstalk coefficient and phase crosstalk coefficient of the difference between the target operating frequency and the measured operating frequency at a second preset threshold are determined as the crosstalk coefficient of the target qubit; It returns the steps of obtaining the target operating frequency for each traversal based on the crosstalk coefficient of the target qubit, the operating frequency of the qubit, the crosstalk coefficient, and the amplitude and phase parameters of the initial microwave signal.

8. The method as described in any one of claims 1 or 6, characterized in that, The correspondence is as follows: Wherein, f0 Qj 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 r is the amplitude parameter 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 phase parameter of the microwave signal applied to the driving line of the i-th qubit. φ is the phase parameter of the microwave signal applied to the driving line of the z-th qubit. 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.

9. A quantum computer, characterized in that, The device includes a quantum processor and a signal source device that provides an initial microwave signal to the driving lines of qubits on the quantum processor; the crosstalk coefficient of the driving lines of the qubits is verified using the verification method for the crosstalk coefficient of the driving lines of qubits as described in any one of claims 1-8.

10. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it can implement the verification method according to any one of claims 1-8 to verify the crosstalk coefficient of the qubit driving line.

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