Waveform distortion calibration method and device, quantum control system, quantum computer

Abstract

The application discloses a waveform distortion calibration method and device, a quantum control system and a quantum computer. First, a set of initial parameters is obtained according to distortion compensation results by using a compensation signal, a frequency modulation signal and a quantum state modulation signal. Then, each parameter corresponding to a maximum ground state probability of a quantum bit in a random benchmark test result in a first range is obtained as a target parameter by using an optimization search algorithm and the random benchmark test. Finally, the value of the initial parameter is updated based on the target parameter, and the compensation signal after the update is used to calibrate the frequency modulation signal of the quantum bit. The application optimizes the parameters of the model of the compensation signal by using the optimization search algorithm, and does not need to perform a large number of measurement sampling operations, thereby effectively improving the measurement efficiency of the waveform distortion and the test efficiency of the quantum chip.

Description

Technical Field

[0001] This invention relates to the field of quantum computing technology, and in particular to a waveform distortion calibration method and apparatus, a quantum control system, and a quantum computer. Background Technology

[0002] Quantum bits are coupled to a flux control circuit. The signal on the flux control circuit is used to control the frequency of the qubit; this flux modulation circuit is also called a frequency modulation line. Flux control circuits typically include components such as bias tees, RC filters, and attenuators. The presence of these components makes the flux control circuit not an ideal circuit. Therefore, when the voltage waveform output from the AWG (Arbitrary Waveform Generator) reaches the qubit, waveform distortion occurs. Examples of waveform distortion are shown below. Figure 1 As shown in the figure, a voltage waveform with amplitude A and time T is applied to the flux control circuit at time t0. The voltage waveform ends at time t0+T, but for a period of time afterward, voltage still exists on the flux control circuit (i.e., the dashed curve in the figure). This is waveform distortion, and the voltage is the distorted voltage waveform. When performing a two-bit gate operation, a voltage waveform needs to be applied to the flux control circuit sequentially. Therefore, the waveform distortion of the previous voltage waveform will affect the subsequent voltage waveform, causing a decrease in the accuracy of the subsequent two-bit gate operation.

[0003] In existing technologies, in order to test the waveform distortion of frequency modulation signals, a large number of measurements and samples need to be taken after time t0+T to obtain the actual waveform distortion. This approach results in the entire testing process consuming a lot of time, which greatly affects the testing efficiency of quantum chips.

[0004] Therefore, improving the testing efficiency of quantum chips has become an urgent problem to be solved in this field.

[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 invention is to provide a waveform distortion calibration method and apparatus, a quantum control system, and a quantum computer to solve the problem of low testing efficiency of quantum chips in the prior art.

[0007] To address the above technical problems, this invention proposes a waveform distortion calibration method for frequency modulation signals of qubits, comprising:

[0008] Using a compensation signal, a frequency modulation signal, and a quantum state modulation signal, a set of initial parameters is obtained based on the distortion compensation result. The initial parameters are the parameters of the model of the compensation signal, and the quantum state modulation signal is used to excite the qubit to an excited state.

[0009] Using random benchmark tests, each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range is taken as the target parameter. The first range is the traversal range of the parameters of the model of the compensation signal that is set in advance. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm.

[0010] The values ​​of the initial parameters are updated based on the target parameters, and the updated compensation signal is used to calibrate the frequency modulation signal of the quantum bit.

[0011] Optionally, the step of obtaining a set of initial parameters based on the distortion compensation result using the compensation signal, frequency modulation signal, and quantum state modulation signal includes:

[0012] At the end of the frequency modulation signal applied to the qubit, a quantum state modulation signal is applied to the qubit;

[0013] At each first time interval, a compensation signal with a different amplitude is applied to the frequency modulation line of the quantum bit to obtain the first change in the probability of the quantum bit being in an excited state as a function of the magnitude of the compensation signal.

[0014] The distortion amplitude is obtained at each moment based on each of the first changes;

[0015] The initial parameters are obtained by fitting each distortion amplitude and the corresponding time using the model of the compensation signal.

[0016] Optionally, the model of the compensation signal is:

[0017]

[0018] Where amp is the distortion amplitude, t is time, and A1, A2, t1, and t2 are the parameters of the compensation signal model.

[0019] Optionally, before performing the process of obtaining a set of initial parameters based on the distortion compensation result using the compensation signal, frequency modulation signal, and quantum state modulation signal, the operating frequency of the qubit is set at a point deviating from the degeneracy point.

[0020] Optionally, the optimized search algorithm is the Nelder-Mead algorithm.

[0021] Optionally, the step of using an optimized search algorithm and random benchmarking to obtain each parameter corresponding to the maximum probability of the qubit being in the ground state in the random benchmarking results within a first range as the target parameter includes:

[0022] The Nelder-Mead algorithm is used to iteratively update the parameters of the compensation signal model within a preset first range. Based on the updated parameters, the random benchmark test is performed on the qubit to obtain the probability that the qubit is in the ground state. When the updated probability is maximized, the corresponding parameter is obtained as the target parameter.

[0023] Optionally, the Z-gate in the random benchmark is prepared by AWG.

[0024] Based on the same inventive concept, this invention also proposes a waveform distortion calibration device for frequency modulation signals of quantum bits, comprising:

[0025] An initial parameter acquisition unit is configured to acquire a set of initial parameters based on the distortion compensation result using a compensation signal, a frequency modulation signal, and a quantum state modulation signal. The initial parameters are parameters of the model of the compensation signal, and the quantum state modulation signal is used to excite the qubit to an excited state.

[0026] The target parameter acquisition unit is configured to use random benchmark tests to acquire each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range as the target parameter. The first range is a pre-set traversal range of the parameters of the model of the compensation signal. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm.

[0027] A calibration unit is configured to update the value of the initial parameter based on the target parameter and to calibrate the frequency modulation signal of the quantum bit using the updated compensation signal.

[0028] Based on the same inventive concept, the present invention also proposes a quantum control system that utilizes the waveform distortion calibration method described in any one of the above-described features, or includes the waveform distortion calibration device described in the above-described features.

[0029] Based on the same inventive concept, the present invention also proposes a quantum computer, including the quantum control system described in the above feature description.

[0030] Based on the same inventive concept, the present invention also proposes a readable storage medium having a computer program stored thereon, which, when executed by a processor, can implement the waveform distortion calibration method described in any of the above-described features.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The waveform distortion calibration method proposed in this invention first obtains a set of initial parameters based on the distortion compensation result using a compensation signal, a frequency modulation signal, and a quantum state modulation signal. Then, using an optimization search algorithm and random benchmark testing, each parameter corresponding to the highest probability of the qubit being in its ground state in the random benchmark test results within a first range is selected as the target parameter. Finally, the values ​​of the initial parameters are updated based on the target parameters, and the updated compensation signal is used to calibrate the frequency modulation signal of the qubit. This application's solution optimizes the parameters of the compensation signal model through an optimization search algorithm, eliminating the need for extensive measurement sampling operations and effectively improving the measurement efficiency of waveform distortion, thereby enhancing the testing efficiency of quantum chips.

[0033] The waveform distortion calibration device, quantum control system, quantum computer, and readable storage medium proposed in this invention belong to the same inventive concept as the waveform distortion calibration method, and therefore have the same beneficial effects, which will not be elaborated here. Attached Figure Description

[0034] Figure 1 This is a schematic diagram illustrating waveform distortion in the prior art.

[0035] Figure 2 This is a schematic flowchart of the waveform distortion calibration method proposed in an embodiment of the present invention;

[0036] Figure 3 This is a simplified structural diagram of a waveform distortion calibration device proposed in another embodiment of the present invention. Detailed Implementation

[0037] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention 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 the present invention.

[0038] In the description of this invention, 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 invention 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 invention.

[0039] 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 invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] Please refer to Figure 1 To test the magnitude of waveform distortion, those skilled in the art often employ a T1 scheme. The T1 scheme involves: first, applying a quantum state modulation signal to the qubit at the end of the frequency modulation signal applied to it; second, applying compensation signals of varying amplitudes to the qubit's frequency modulation line at regular time intervals, and obtaining the first change in the probability of the qubit being in an excited state as a function of the compensation signal amplitude; and third, obtaining the corresponding distortion amplitude based on the amplitude corresponding to the maximum probability point of the qubit being in an excited state in the first change. In existing technologies, the T1 scheme needs to be executed multiple times to ensure the accuracy of waveform distortion, consuming a significant amount of testing time and severely impacting the testing efficiency of quantum chips.

[0041] Please refer to Figure 2 To improve the testing efficiency of quantum chips, this invention proposes a waveform distortion calibration method for frequency modulation signals of quantum bits, comprising:

[0042] S100: Using the compensation signal, frequency modulation signal, and quantum state modulation signal, a set of initial parameters is obtained based on the distortion compensation result. The initial parameters are the parameters of the model of the compensation signal. The quantum state modulation signal is used to excite the quantum bit to the excited state.

[0043] S200: Using random benchmark tests, each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range is obtained as the target parameter. The first range is the traversal range of the parameters of the model of the compensation signal that is preset. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm.

[0044] S300: Update the value of the initial parameter based on the target parameter, and calibrate the frequency modulation signal of the quantum bit with the updated compensation signal.

[0045] Unlike existing technologies, the waveform distortion calibration method proposed in this embodiment first obtains a set of initial parameters based on the distortion compensation result using a compensation signal, a frequency modulation signal, and a quantum state modulation signal. Then, using an optimization search algorithm and random benchmark testing, it obtains each parameter corresponding to the highest probability of the qubit being in its ground state within a first range of random benchmark test results as the target parameter. Finally, it updates the values ​​of the initial parameters based on the target parameters, and uses the updated compensation signal to calibrate the frequency modulation signal of the qubit. This application's solution optimizes the parameters of the compensation signal model through an optimization search algorithm, eliminating the need for extensive measurement sampling operations and effectively improving the measurement efficiency of waveform distortion, thereby increasing the testing efficiency of quantum chips. Using this application's solution, it eliminates the need to repeatedly execute the T1 scheme; only one T1 scheme is required to obtain the initial parameters, effectively solving the problem of excessive time consumption from multiple T1 schemes.

[0046] It is important to note that the optimization search algorithm described herein is a method that utilizes the high performance of a computer to purposefully exhaustively search for some or all possible solutions to a problem, thereby finding a solution. This includes, but is not limited to, enumeration algorithms, depth-first search, breadth-first search, A* algorithm, backtracking algorithms, Monte Carlo tree search, hash functions, and other algorithms. In this embodiment, the optimization search algorithm is the Nelder-Mead algorithm, which is an algorithm for finding local minima of a multivariate function. Other types of optimization search algorithms can also be used, which will not be elaborated upon here.

[0047] Specifically, in this embodiment, the initial parameters can be obtained through the T1 scheme, that is, by using the compensation signal, the frequency modulation signal, and the quantum state modulation signal, a set of initial parameters is obtained based on the distortion compensation result, including:

[0048] At the end of the frequency modulation signal applied to the qubit, a quantum state modulation signal is applied to the qubit;

[0049] At each first time interval, a compensation signal with a different amplitude is applied to the frequency modulation line of the quantum bit to obtain the first change in the probability of the quantum bit being in an excited state as a function of the magnitude of the compensation signal.

[0050] The distortion amplitude is obtained at each moment based on each of the first changes;

[0051] The initial parameters are obtained by fitting each distortion amplitude and the corresponding time using the model of the compensation signal.

[0052] Specifically, in this embodiment, the model of the compensation signal is as follows:

[0053]

[0054] Where amp is the distortion amplitude, t is time, and A1, A2, t1, and t2 are the parameters of the compensation signal model.

[0055] As will be understood by those skilled in the art, in this embodiment, the model of the compensation signal is a parametric model, where A1, A2, t1, and t2 are the parameters of the compensation signal model. By using a T1 scheme, data on the change of distortion amplitude over time can be obtained. By fitting these data through the compensation signal model, a set of values ​​for A1, A2, t1, and t2 can be obtained, and this set of values ​​is the initial parameter.

[0056] Specifically, in this embodiment, before performing the process of obtaining a set of initial parameters based on the distortion compensation result using the compensation signal, frequency modulation signal, and quantum state modulation signal, the operating frequency of the qubit is set at a point deviating from the degeneracy point. Those skilled in the art will understand that the degeneracy point refers to the point at which the qubit is insensitive to the magnetic flux modulation signal (i.e., the frequency modulation signal) at the current frequency. In this embodiment, adjusting the operating frequency of the qubit away from the degeneracy point is to make the qubit more sensitive to the magnetic flux modulation signal, facilitating the observation of waveform distortion.

[0057] Optionally, the step of using the Nelder-Mead algorithm and random benchmarking to obtain each parameter corresponding to the maximum probability of the qubit being in the ground state in the random benchmarking results within a first range as the target parameter includes:

[0058] The Nelder-Mead algorithm is used to iteratively update the parameters of the compensation signal model within a preset first range. Based on the updated parameters, the random benchmark test is performed on the qubit to obtain the probability that the qubit is in the ground state. When the updated probability is maximized, the corresponding parameter is obtained as the target parameter.

[0059] It should be noted that the Nelder-Mead algorithm is an iterative optimization strategy based on the concept of a simplex to construct solutions. For an N-dimensional optimization problem, the Nelder-Mead algorithm first selects N+1 points to form an initial simplex. Then, it iteratively updates the vertices of the simplex using a series of manually designed rules, ensuring that the generated simplex converges towards a local minimum. In each iteration, the objective function value is calculated for each point of the simplex, and the point with the largest objective function value is replaced by another point, until the simplex converges to a local minimum of the objective function. The general process is as follows:

[0060] Compare the function values ​​of all simplex vertices and find the simplex vertex with the largest and smallest function values. Then calculate the centroids of all other simplex vertices except the one with the largest function value. Along the line connecting the simplex vertex with the largest function value and the centroid, calculate the reflection point, extension point, and compression point of the simplex vertex with the largest function value. If no reflection point, extension point, or compression point is found, calculate a contraction point on the line segment from the simplex vertex with the largest function value to the simplex vertex with the smallest function value. If an optimal point exists among the reflection point, extension point, compression point, and contraction point, use this optimal point as a new simplex vertex to replace the simplex vertex with the largest function value and reconstruct the N+1 dimensional simplex. Continue this process until a simplex vertex with the smallest function value is found.

[0061] The Nelder-Mead algorithm adheres to the fundamental principle of ensuring that each iteration is better than the previous one. It first finds a basic feasible solution and checks if it is the optimal solution. If not, it iterates according to certain rules to another improved basic feasible solution, then checks it again. If it is still not optimal, it iterates again, repeating this process. Because the number of basic feasible solutions is finite, the optimal solution to the problem can be obtained after a finite number of iterations.

[0062] In this embodiment, finding the optimal parameters of the compensation signal model is the optimization problem of the Nelder-Mead algorithm. The parameters of the compensation signal model include any one or more elements from A1, A2, t1, and t2, which constitute the dimension N of the optimization problem. The N+1 sets of parameters are the simplex vertices of the Nelder-Mead algorithm. Solving for the probability that the qubit is in an excited state based on specific parameters is the objective function of the Nelder-Mead algorithm. It should be noted that in this embodiment, the parameters optimized using the Nelder-Mead algorithm may also include the amplitude of the Z-gate. The optimization range of the parameters is determined based on the initial parameters and can be set near the initial parameters.

[0063] In this embodiment, the Z-gate in the randomized benchmark is prepared using an AWG. Since the Z-gate is applied through the frequency modulation line of the qubit, the signal distortion of the frequency modulation signal on the frequency modulation line can be effectively obtained. Those skilled in the art will understand that the randomized benchmark (RB test) includes single-bit RB and two-bit RB. The single-bit RB is a randomized benchmark based on the Clifford group. The single-bit Clifford group has 24 elements. We can use several basic gate operations, that is, the logic gates of the qubit to be characterized, to construct the elements in the Clifford group. The set of basic gate operations is S = {I, ±X, ±Y, ±X / 2, ±Y / 2}. We randomly select m group elements (m is also called the gate depth) from the Clifford group and apply them sequentially to the qubit. According to the definition of a group, there must exist an inverse in the Clifford group such that this series of operations is equivalent to a unit gate, which is then applied to the qubit. If all operations are perfect, then the qubit should be in the |0> state. The probability of the qubit being in the |0> state is measured as the guarantee of the sequence. For each m, the average guarantee of the sequence is P obtained by repeating the experiment k times. m Change the value of m and repeat the above steps to obtain a set {P}. m}. {P m}Use formula P m =Ap m The initial state preparation and measurement errors are included in the fitting results A and B, obtained by fitting the parameters p. The error of a Clifford operation, r = 0.5*(1-p), can be calculated based on the fitting parameter p. Since a Clifford operation contains 1.875 basic gates in S, the average fidelity of the basic gate operations in S is 1-r / 1.875. Thus, we can obtain the average fidelity of a single-bit gate. The execution process of single-bit RB is similar to that of two-bit RB, the difference being that the Clifford in single-bit RB experiments consists entirely of single-bit gates, while the Clifford in two-bit RB experiments contains both single-bit and two-bit gates. Random benchmark operations also include Z-gates. Typical random benchmark Z-gate operations are usually implemented using a combination of X and Y gates. In this embodiment, to obtain the signal distortion of the frequency modulation signal on the frequency modulation line, the Z-gate is directly prepared using an AWG and output to the quantum bit through the frequency modulation line.

[0064] Please refer to Figure 3 Based on the same inventive concept, this invention also proposes a waveform distortion calibration device for frequency modulation signals of qubits, comprising:

[0065] The initial parameter acquisition unit 100 is configured to acquire a set of initial parameters based on the distortion compensation result using a compensation signal, a frequency modulation signal, and a quantum state modulation signal. The initial parameters are the parameters of the model of the compensation signal, and the quantum state modulation signal is used to excite the qubit to an excited state.

[0066] The target parameter acquisition unit 200 is configured to acquire each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range as the target parameter using random benchmark tests. The first range is a pre-set traversal range of the parameters of the model of the compensation signal. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm.

[0067] The calibration unit 300 is configured to update the value of the initial parameter based on the target parameter and to calibrate the frequency modulation signal of the quantum bit with the updated compensation signal.

[0068] It is understood that the initial parameter acquisition unit 100, the target parameter acquisition unit 200, and the calibration unit 300 can be implemented in a single device, or any one of these modules can be split into multiple sub-modules. Alternatively, at least some of the functions of one or more modules of the initial parameter acquisition unit 100, the target parameter acquisition unit 200, and the calibration unit 300 can be combined with at least some of the functions of other modules and implemented in a single functional module. According to embodiments of the present invention, at least one of the initial parameter acquisition unit 100, the target parameter acquisition unit 200, and the calibration unit 300 can be at least partially implemented as hardware circuitry, such as a field-programmable gate array (FPGA), a programmable logic array (PLA), a system-on-a-chip, a system-on-a-substrate, a system-on-package, an application-specific integrated circuit (ASIC), or can be implemented in hardware or firmware in any other reasonable manner by integrating or packaging the circuitry, or in a suitable combination of software, hardware, and firmware implementations. Alternatively, at least one of the initial parameter acquisition unit 100, the target parameter acquisition unit 200, and the calibration unit 300 may be implemented at least partially as a computer program module, which can perform the functions of the corresponding module when the program is run by a computer.

[0069] Based on the same inventive concept, embodiments of the present invention also propose a quantum control system that utilizes the waveform distortion calibration method described in any one of the above-described features, or includes the waveform distortion calibration device described in the above-described features.

[0070] Based on the same inventive concept, embodiments of the present invention also propose a quantum computer, including the quantum control system described in the above feature description.

[0071] Based on the same inventive concept, embodiments of the present invention also propose a readable storage medium storing a computer program thereon, which, when executed by a processor, can implement the waveform distortion calibration method described in any of the above-described features.

[0072] The 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. The network can include copper transmission cables, fiber optic transmission, wireless transmission, 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 in a readable storage medium within the respective computing / processing device. The computer program used to perform the operations of this invention 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, thereby realizing various aspects of the present invention.

[0073] Various aspects of the present invention are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products according to embodiments of the invention. 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 comprises an article of manufacture including instructions for implementing aspects of the functions / actions specified in one or more blocks of the flowchart illustrations and / or block diagrams.

[0074] 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.

[0075] In the description of this specification, 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 the invention. 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.

[0076] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A method for calibrating waveform distortion, characterized in that, Frequency modulation signals used for quantum bits include: Using a compensation signal, a frequency modulation signal, and a quantum state modulation signal, a set of initial parameters is obtained based on the distortion compensation result. The initial parameters are the parameters of the model of the compensation signal, and the quantum state modulation signal is used to excite the qubit to an excited state. Using random benchmark tests, each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range is taken as the target parameter. The first range is the traversal range of the parameters of the model of the compensation signal that is set in advance. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm. The values ​​of the initial parameters are updated based on the target parameters, and the frequency modulation signal of the quantum bit is calibrated according to the updated compensation signal.

2. The method as described in claim 1, characterized in that, The method utilizes compensation signals, frequency modulation signals, and quantum state modulation signals to obtain a set of initial parameters based on the distortion compensation results, including: At the end of the frequency modulation signal applied to the qubit, a quantum state modulation signal is applied to the qubit; At each first time interval, a compensation signal with a different amplitude is applied to the frequency modulation line of the quantum bit to obtain the first change in the probability of the quantum bit being in an excited state as a function of the magnitude of the compensation signal. The distortion amplitude is obtained at each moment based on each of the first changes; The initial parameters are obtained by fitting each distortion amplitude and the corresponding time using the model of the compensation signal.

3. The method as described in claim 2, characterized in that, The model of the compensation signal is as follows: Where amp is the distortion amplitude, t is time, and A1, A2, t1, and t2 are the parameters of the compensation signal model.

4. The method as described in claim 1, characterized in that, Before performing the process of obtaining a set of initial parameters based on the distortion compensation result using the compensation signal, frequency modulation signal, and quantum state modulation signal, the operating frequency of the quantum bit is set at a point deviating from the degeneracy point.

5. The method as described in claim 1, characterized in that, The optimized search algorithm is the Nelder-Mead algorithm.

6. The method as described in claim 5, characterized in that, Using an optimized search algorithm and random benchmark tests, the target parameters are obtained as follows: (The parameters are defined as follows:) The Nelder-Mead algorithm is used to iteratively update the parameters of the compensation signal model within a preset first range. Based on the updated parameters, the random benchmark test is performed on the qubit to obtain the probability that the qubit is in the ground state. When the updated probability is maximized, the corresponding parameter is obtained as the target parameter.

7. The method as described in claim 6, characterized in that, The Z-gate in the randomized benchmark test was prepared using an AWG.

8. A waveform distortion calibration device, characterized in that, Frequency modulation signals used for quantum bits include: An initial parameter acquisition unit is configured to acquire a set of initial parameters based on the distortion compensation result using a compensation signal, a frequency modulation signal, and a quantum state modulation signal. The initial parameters are parameters of the model of the compensation signal, and the quantum state modulation signal is used to excite the qubit to an excited state. The target parameter acquisition unit is configured to use random benchmark tests to acquire each parameter corresponding to the highest probability of the qubit being in the ground state in the random benchmark test results within a first range as the target parameter. The first range is a pre-set traversal range of the parameters of the model of the compensation signal. The value of the parameter to be traversed each time within the first range is determined by an optimized search algorithm. A calibration unit is configured to update the value of the initial parameter based on the target parameter and to calibrate the frequency modulation signal of the quantum bit according to the updated compensation signal.

9. A quantum control system, characterized in that, The waveform distortion calibration method according to any one of claims 1-7, or the waveform distortion calibration apparatus according to claim 8.

10. A quantum computer, characterized in that, Includes the quantum control system described in claim 9.

11. 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 waveform distortion calibration method according to any one of claims 1 to 7.

Images