Parameter space freedom degree determination method and device, electronic equipment and storage medium

Abstract

The embodiment of the invention provides a parameter space degree of freedom determination method and device, electronic equipment and a storage medium, and the scheme is as follows: according to a first working frequency and a second working frequency corresponding to a first quantum bit and a second quantum bit under the condition that the frequency detuning is 0, and a third working frequency of an adjustable coupler under a preset gate length, determining the degree of freedom of a parameter space; calculating target coupling strength; according to periodic quantum logic gate operations on the first quantum bit and the second quantum bit under different frequency detuning conditions, obtaining a first corresponding relation between frequency detuning and a leakage rate, and obtaining a second corresponding relation between frequency detuning and a preset condition phase; and based on the first corresponding relation and the second corresponding relation, obtaining first detuning and second detuning corresponding to the lowest leakage rate under the target phase as target detuning parameters. According to the technical scheme provided by the embodiment of the invention, the influence of the distortion of the residual short time scale on the magnetic flux control line on the quantum calculation process can be avoided, so that the fidelity of quantum calculation is improved.

Description

Technical Field

[0001] This application relates to the field of quantum computing technology, and in particular to a method, apparatus, electronic device and storage medium for determining the degrees of freedom in parameter space. Background Technology

[0002] Quantum computing is a computational paradigm that utilizes the fundamental properties of quantum mechanics to solve problems. By constructing precisely operable quantum physics hardware systems and running quantum computing software to implement quantum algorithms, computational problems can be solved, enabling the application of quantum computing in specific problems or fields.

[0003] In quantum computing, the presence of short-timescale distortions (STDs) disrupts the edges of rapid rises and falls in short-timescale waveforms, thus affecting the quantum computing results. Summary of the Invention

[0004] The purpose of this application is to provide a method, apparatus, electronic device, and storage medium for determining the degrees of freedom in parameter space, so as to avoid the influence of residual short-timescale distortions on the flux control line on the quantum computing process, thereby improving the fidelity of quantum computing. The specific technical solution is as follows:

[0005] This application provides a method for determining the degrees of freedom in a parameter space, the method comprising:

[0006] The target coupling strength between the first and second qubits is calculated based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. The tunable coupler is used to couple the first and second qubits.

[0007] Based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate is obtained, and a second correspondence between frequency detuning and preset condition phase is obtained. Each frequency detuning condition includes a first detuning and a second detuning. The first detuning and the second detuning are the frequency differences corresponding to the control waveforms of the periodic quantum logic gate operations in different time periods within the same time period.

[0008] Based on the first correspondence and the second correspondence, the first detuning and the second detuning with the lowest leakage rate under the target phase are obtained as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0009] This application embodiment also provides a parameter space degrees of freedom determination device, the device comprising:

[0010] The calculation module is used to calculate the target coupling strength between the first quantum bit and the second quantum bit based on the first operating frequency and the second operating frequency corresponding to the first quantum bit and the second quantum bit when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. The tunable coupler is used to couple the first quantum bit and the second quantum bit.

[0011] The first acquisition module is used to acquire, based on the target coupling strength and according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate, and a second correspondence between frequency detuning and preset condition phase. Each frequency detuning condition includes a first detuning and a second detuning, where the first detuning and the second detuning are the frequency differences corresponding to the control waveforms of the periodic quantum logic gate operations in different time periods within the same time period.

[0012] The second acquisition module is used to acquire the first detuning and the second detuning with the lowest leakage rate under the target phase as target detuning parameters based on the first correspondence and the second correspondence, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0013] This application also provides an electronic device, including a processor, a communication interface, a memory, and a communication bus, wherein the processor, the communication interface, and the memory communicate with each other through the communication bus;

[0014] Memory, used to store computer programs;

[0015] When a processor executes a program stored in memory, it implements any of the steps of the parameter space degree of freedom determination method described above.

[0016] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the parameter space degree of freedom determination method described above.

[0017] This application also provides a computer program product containing instructions that, when run on a computer, cause the computer to execute any of the parameter space degree of freedom determination methods described above.

[0018] Beneficial effects of the embodiments in this application:

[0019] The technical solution provided in this application can calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler under a preset gate length. Based on the target coupling strength, and according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate, and a second correspondence between frequency detuning and qubit phase are obtained. Thus, the target detuning parameters, namely the first detuning and the second detuning, are determined based on the first and second correspondences.

[0020] The presence of STDs (Standard Degrees of Freedom) causes the number of degrees of freedom during periodic quantum logic gate operations to be less than the number of constraints, thus affecting the quantum computing results. Therefore, compared to related technologies that only use coupling strength and one frequency detuning as the degree of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space, the embodiments of this application introduce two detunings during the determination of the degree of freedom in the parameter space, namely the first detuning and the second detuning. This increases the number of degrees of freedom in the parameter space during the periodic quantum logic gate operation to a state that matches the constraints during the quantum logic gate operation, effectively avoiding the influence of STDs on the periodic quantum logic gate operation, that is, avoiding the influence of residual short-timescale distortions on the flux control line on the quantum computing process, thereby improving the fidelity of quantum computing.

[0021] In addition, the first and second detunings in the parameter space degrees of freedom are the frequency detunings corresponding to the lowest leakage rate under the target phase. This ensures that the determined first and second detunings can satisfy the leakage and phase conditions corresponding to the control waveform, guaranteeing the accuracy of the determined target detuning parameters and thus improving the fidelity of quantum computing.

[0022] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of a flat-top Gaussian waveform provided in an embodiment of this application;

[0025] Figure 2A schematic flowchart of a first method for determining the degrees of freedom of the parameter space provided in an embodiment of this application;

[0026] Figure 3 This is a schematic flowchart of a target coupling strength calculation method provided in an embodiment of this application;

[0027] Figure 4 A flowchart illustrating a method for obtaining correspondence provided in an embodiment of this application;

[0028] Figure 5 A flowchart illustrating the first correspondence provided in an embodiment of this application;

[0029] Figure 6 A schematic diagram of the transformation relationship provided in the embodiments of this application;

[0030] Figure 7 A flowchart illustrating a second correspondence acquisition method provided in an embodiment of this application;

[0031] Figure 8 A flowchart illustrating a method for obtaining target detuning parameters provided in an embodiment of this application;

[0032] Figure 9 A second flowchart illustrating the method for determining the degrees of freedom in the parameter space provided in this application embodiment;

[0033] Figure 10 A schematic diagram illustrating the CZ gate operation fidelity provided in an embodiment of this application;

[0034] Figure 11 A schematic diagram of a third method for determining the degrees of freedom of the parameter space provided in an embodiment of this application;

[0035] Figure 12 A schematic diagram of the fourth method for determining the degrees of freedom of the parameter space provided in the embodiments of this application;

[0036] Figure 13 A schematic diagram of a parameter space degree-of-freedom determination device provided in an embodiment of this application;

[0037] Figure 14 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0038] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0039] In related technologies, residual coupling can be suppressed through tunable coupling to improve the fidelity of quantum logic gate operations. However, the presence of STD disrupts the edges of rapid rises and falls in short-timescale waveforms. For ease of understanding, let's combine... Figure 1 To explain, Figure 1 This is a schematic diagram of a flat-top Gaussian waveform provided in an embodiment of this application. The flat-top Gaussian waveform can be used as the control waveform for a controlled-Z (CZ) gate. Figure 1 In the diagram, curve 101 represents an ideal flat-top Gaussian wave, unaffected by STD. Curve 102 represents a flat-top Gaussian wave affected by STD. Compared to curve 101, curve 102 exhibits distortion at both the falling and rising edges. This distortion disrupts the time symmetry of the flat-top Gaussian wave, thus affecting the dynamic evolution of the quantum logic gate based on it, disrupting the periodicity of the evolution, leading to phase errors, and reducing the fidelity of quantum logic gate operations.

[0040] Taking the CZ gate as an example, without a standard deviation (STD), constrained by both leakage rate and phase, CZ gate operations can be implemented in the parameter space S = {(g,Δ)|g∈G,Δ∈D} with g and Δ as degrees of freedom. Here, g represents the coupling strength, Δ represents the frequency detuning between qubits (which can be expressed as the frequency difference between qubits), and G and D represent the feasible ranges corresponding to the coupling strength and frequency detuning, respectively. Under these conditions, the number of degrees of freedom is the same as the number of constraints, and a feasible solution can be obtained in the parameter space. However, when an STD exists, since the STD is an unknown constraint, the number of constraints increases, leading to an imbalance between the number of degrees of freedom and the number of constraints. In this case, a feasible solution cannot be obtained in the parameter space, severely affecting the fidelity of quantum logic gate operations.

[0041] To address the problems in related technologies, embodiments of this application provide a method for determining the degrees of freedom in a parameter space. For example... Figure 2 As shown, Figure 2 This is a schematic flowchart of a first method for determining the degrees of freedom in the parameter space provided in an embodiment of this application. This method can be applied to any electronic device, such as a quantum computer or a quantum computing control system; however, no specific limitation is made to this electronic device. Figure 2 The method shown includes the following steps.

[0042] Step S201: Calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. The tunable coupler is used to couple the first and second qubits.

[0043] Step S202: Based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, obtain the first correspondence between frequency detuning and leakage rate, and obtain the second correspondence between frequency detuning and preset condition phase. Each frequency detuning condition includes the first detuning and the second detuning. The first detuning and the second detuning are the frequency differences corresponding to the control waveforms of the periodic quantum logic gate operations in different time periods within the same time period.

[0044] Step S203: Based on the first correspondence and the second correspondence, obtain the first detuning and the second detuning with the lowest leakage rate under the target phase as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0045] pass Figure 2 The method shown can calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. Based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate and a second correspondence between frequency detuning and qubit phase are obtained. Thus, the target detuning parameters, namely the first detuning and the second detuning, are determined based on the first and second correspondences.

[0046] The presence of STDs (Standard Degrees of Freedom) causes the number of degrees of freedom during periodic quantum logic gate operations to be less than the number of constraints, thus affecting the quantum computing results. Therefore, compared to related technologies that only use coupling strength and one frequency detuning as the degree of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space, the embodiments of this application introduce two detunings during the determination of the degree of freedom in the parameter space, namely the first detuning and the second detuning. This increases the number of degrees of freedom in the parameter space during the periodic quantum logic gate operation to a state that matches the constraints during the quantum logic gate operation, effectively avoiding the influence of STDs on the periodic quantum logic gate operation, that is, avoiding the influence of residual short-timescale distortions on the flux control line on the quantum computing process, thereby improving the fidelity of quantum computing.

[0047] In addition, the first and second detunings in the parameter space degrees of freedom are the frequency detunings corresponding to the lowest leakage rate under the target phase. This ensures that the determined first and second detunings can satisfy the leakage and phase conditions corresponding to the control waveform, guaranteeing the accuracy of the determined target detuning parameters and thus improving the fidelity of quantum computing.

[0048] The embodiments of this application will be described below through specific examples.

[0049] Regarding step S201 above, that is, based on the first operating frequency and the second operating frequency corresponding to the first quantum bit and the second quantum bit when the frequency detuning is 0, and the third operating frequency of the tunable coupler under the preset gate length, the target coupling strength between the first quantum bit and the second quantum bit is calculated, and the tunable coupler is used to couple the first quantum bit and the second quantum bit.

[0050] For ease of understanding, the following explanation will only use two qubits on a quantum chip, namely the first qubit and the second qubit, as an example. The first qubit and the second qubit are coupled through a tunable coupler.

[0051] The electronic device can obtain the operating frequencies corresponding to the first and second qubits respectively when the frequency detuning is 0. That is, it can obtain the first operating frequency of the first qubit and the second operating frequency of the second qubit.

[0052] In an optional embodiment, the electronic device can obtain an AC spectrum based on the correspondence between frequency and amplitude, and then determine the operating frequencies corresponding to the first and second qubits, i.e., the aforementioned first and second operating frequencies, based on the AC spectrum. For details on the method of determining the first and second operating frequencies using the AC spectrum, please refer to the determination methods in related technologies; specific details will not be provided here.

[0053] For tunable couplers, before performing periodic quantum logic gate operations using the first and second qubits, it is necessary to configure the parameters of the first and second qubits and the tunable coupler, such as local oscillator information and channel information, including the preset gate length of the tunable coupler. The electronic device can obtain the third operating frequency of the tunable coupler at the preset gate length. This preset gate length is the duration of the periodic quantum logic gate operation. For ease of understanding, a CZ gate operation is used as an example, where the preset gate length is the duration of one CZ gate operation.

[0054] The preset door lengths mentioned above are pre-set according to user needs, etc. No specific limitations are made regarding the preset door lengths here.

[0055] The electronic device can calculate the coupling strength between the first and second qubits based on the first, second, and third operating frequencies mentioned above, and use this as the target coupling strength. This target coupling strength is the coupling strength of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space degrees of freedom. The calculation method for the target coupling strength is described below and will not be elaborated upon here.

[0056] In the embodiments of this application, the aforementioned periodic quantum logic gate operation can be a periodic two-quantum logic gate operation. For example, the periodic quantum logic gate operation can be a CZ gate operation or a controlled-phase (CPhase) gate operation in a two-quantum logic gate operation. For ease of understanding, the following description only uses a CZ gate operation as an example of a periodic quantum logic gate operation and does not serve any limiting purpose.

[0057] Regarding step S202 above, that is, based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate is obtained, and a second correspondence between frequency detuning and preset condition phase is obtained. Each frequency detuning condition includes a first detuning and a second detuning. The first detuning and the second detuning are the frequency differences corresponding to the control waveforms of periodic quantum logic gate operations in different time periods within the same time period.

[0058] In this embodiment, applying a voltage change to the control waveform onto the adjustable coupler can change the coupling strength between the first and second qubits. Therefore, once the target coupling strength is determined, the voltage of the control waveform applied to the adjustable coupler will also be determined.

[0059] Given a fixed target coupling strength, i.e., a fixed control waveform voltage for the tunable coupler, the electronic device can perform multiple periodic quantum logic gate operations on the first and second qubits based on different frequency detuning conditions. The frequency detuning condition corresponding to each periodic quantum logic gate operation is different. Based on each periodic quantum logic gate operation, the electronic device can obtain a first correspondence between frequency detuning and leakage rate, and a second correspondence between frequency detuning and the preset condition phase.

[0060] Each of the above frequency detuning conditions includes a first detuning and a second detuning. The first detuning and the second detuning are the frequency differences corresponding to different time periods of the control waveform of the periodic quantum logic gate operation within the same time period. For ease of understanding, refer to the above... Figure 1 Let's take an example. During the aforementioned periodic quantum logic gate operation, the electronic device can apply the control waveform of the periodic quantum logic gate operation to the first qubit, the second qubit, and the Z-line of the tunable coupler. Within each time period, the electronic device can respectively... Figure 1 The frequency difference between the first and second qubits is changed during time periods 103 and 104, as shown. The frequency difference changed during time period 103 is denoted as the first detuning, and the frequency difference changed during time period 104 is denoted as the second detuning.

[0061] In this embodiment, since the Hamiltonian of the aforementioned periodic quantum logic gate is implemented in the |11>-|20 subspace, the aforementioned preset conditional phase... It can be represented as: in, The phase of |11> The phase of |10> The phase of |00> The phase of |01>.

[0062] In an optional embodiment, the first correspondence can be a correspondence between the first detuning, the second detuning, and the leakage rate. The second correspondence can be a correspondence between the first detuning, the second detuning, and the preset condition phase. The methods for obtaining the first and second correspondences are described below and will not be specifically explained here.

[0063] Regarding step S203 above, that is, based on the first correspondence and the second correspondence, the first detuning and the second detuning with the lowest leakage rate under the target phase are obtained as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0064] In this step, after obtaining the aforementioned first and second correspondences, the electronic device can determine the first and second detunings corresponding to the preset condition phase as the target phase and the lowest leakage rate, and use the determined first and second detunings as target detuning parameters. These target detuning parameters are the frequency detunings of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space degrees of freedom.

[0065] For ease of understanding, the symmetry analysis of the Hamiltonian and constraints of the system under periodic control is as follows:

[0066] make In the known In this case, define Given Since H = H + U = U + Therefore, we can obtain Hermitian operators (U=ULt=U+1,2U*,UU+=1) satisfy Uψα=ψ0.

[0067] In the symmetric case, H(t) = H(τ-t), when hour, make but

[0068] Among them, U L This is the time evolution operator for t→0, where t is time. Let be a time-ordered evolution operator, and exp be an exponential function with base e. To reduce Planck's constant, i is the imaginary unit. For the integration operation from t→0, H(t) is the Hamiltonian that varies with time, U R Let be the time evolution operator from t to τ, where τ is the end time of the corresponding waveform, e is the natural constant, H is the Hamiltonian, I is the identity matrix, ψ(0) is the state vector of the system at time 0, and n is the complete eigenvector of ψ. The dimension of the expansion is α1, where α1 is the phase. For complete eigenvectors, V is a diagonal matrix with imaginary terms eliminated, and H is... + Let H be the Hermitian conjugate of H, and let U be the time evolution operator that theoretically satisfies U|ψ(α)>=|ψ(0)>. + For the Hermitian conjugate of U, U * For the complex conjugate of U, (ψ(0)>) *Let t′ be the complex conjugate of |ψ(0)>, and t′ be a certain moment in the distorted case where |ψ(t′)>=|ψ(α)> is satisfied. Let |ψ(α)> be the complex conjugate of |ψ(0)>. * The state vector.

[0069] Therefore, in the symmetric case, the two degrees of freedom g and Δ in the parameter space S={(g,Δ)} can already satisfy the dual constraints of leakage condition and phase condition.

[0070] In the asymmetric case, U L (t′)=U, which is related to U R (t′) is irrelevant, therefore U R (t′)=U is another constraint. This will cause the two degrees of freedom g and Δ in the existing parameter space S={(g,Δ)} to be unable to meet the practical requirements. Therefore, for scenarios with STD, i.e., under time asymmetry, the parameter space S={(g,Δ)} is expanded to S′={(g,Δ1,Δ2)}, where Detune1 is the first detuning parameter in the target detuning parameters and Δ2 is the second detuning parameter in the target detuning parameters. By expanding the degrees of freedom in the parameter space, the number of degrees of freedom in the parameter space can be matched with the number of constraints, thereby satisfying the time asymmetry, avoiding the influence of STD on the two-word computation process, and improving the fidelity of quantum computing.

[0071] In an optional embodiment, according to the above... Figure 2 The method shown in this application embodiment also provides a method for calculating target coupling strength. For example... Figure 3 As shown, Figure 3 This is a flowchart illustrating a method for calculating target coupling strength provided in an embodiment of this application. The method includes the following steps.

[0072] Step S301: Through a SWAP experiment on the first and second qubits, determine the operating frequency corresponding to the resonance of the first and second qubits, and obtain the first and second operating frequencies.

[0073] In this step, the electronic device can fix the operating frequency of either the first or second qubit, and perform a swap experiment between the first and second qubits by adjusting the operating frequency of the other qubit. During the swap experiment, when the first and second qubits resonate, they will exchange quantum states. The moment of quantum state exchange is the moment of resonance between the first and second qubits. At this point, the electronic device can determine the operating frequency corresponding to the resonance of the first and second qubits.

[0074] For ease of understanding, let's take a fixed operating frequency of the first qubit as an example. The electronic device can fix the operating frequency of the first qubit to w1, which is the aforementioned first operating frequency. In this case, the electronic device can perform a SWAP experiment on the first and second qubits. During the SWAP experiment, the operating frequency w2 of the second qubit is continuously adjusted. The electronic device can obtain w2 of the second qubit during quantum state swapping, thus obtaining the aforementioned second operating frequency.

[0075] The aforementioned fixed operating frequency, such as w1, can be set based on user experience or the operating frequency calculated from the AC spectrum. The method for determining the fixed operating frequency is not specifically limited here. Furthermore, the SWAP experiment on the first and second qubits can be performed using relevant technical methods, and will not be specifically described here.

[0076] In the embodiments of this application, when the first quantum bit and the second quantum bit resonate, it can be determined that the frequency detuning between the first quantum bit and the second quantum bit is 0.

[0077] Compared to the method of determining the first and second operating frequencies through AC spectrum, the method of obtaining the first and second operating frequencies through SWAP experiment in step S301 can effectively improve the accuracy of the determined first and second operating frequencies, thereby improving the accuracy of the target coupling strength calculated based on the first and second operating frequencies in the later stage.

[0078] Step S302: Under the condition of voltage change on the tunable coupler, the third operating frequency of the tunable coupler at the preset gate length is determined by SWAP experiment on the first and second qubits.

[0079] In this step, the electronic device alters the coupling strength between the first and second qubits by changing the voltage of the control waveform applied to the tunable coupler, thus changing the interaction between them. When the operating frequency of the tunable coupler matches the resonant frequency of the two coupled qubits (i.e., the first and second qubits), quantum state exchange occurs between the two qubits. Therefore, the electronic device can perform a SWAP experiment on the first and second qubits by changing the voltage applied to the tunable coupler, and determine the voltage applied to the tunable coupler during quantum state exchange. Based on this voltage, a third operating frequency of the tunable coupler at a preset gate length can be determined. This third operating frequency can be obtained through fitting. The method for obtaining the third operating frequency can be found in related technologies and will not be specifically described here.

[0080] Step S303: Calculate the target coupling strength between the first qubit and the second qubit based on the first operating frequency, the second operating frequency, and the third operating frequency.

[0081] In an optional embodiment, step S303 above, namely calculating the target coupling strength between the first qubit and the second qubit based on the first operating frequency, the second operating frequency, and the third operating frequency, can be specifically expressed as:

[0082] Electronic devices use the following formula to calculate the target coupling strength between the first quantum bit and the second quantum bit;

[0083]

[0084] Where g is the target coupling strength, w1 is the first operating frequency, w2 is the second operating frequency, and w c For the third operating frequency, 1 / Δ = (1 / Δ1 + 1 / Δ2) / 2, Δ i The frequency difference between the quantum bit and the tunable coupler. C 1c C is the coupling capacitance between the first quantum bit and the tunable coupler. 2c C is the coupling capacitance between the second qubit and the tunable coupler. 12 C is the coupling capacitance between the first and second qubits. c The capacitor is for the adjustable coupler. Σ j =ω j +ω c The sum of the frequencies of the qubit and the tunable coupler, i and j represent the first qubit or the second qubit, C1 is the capacitance of the first qubit, and C2 is the capacitance of the second qubit.

[0085] Steps S301-S303 above are a refinement of step S201 above.

[0086] Through steps S301-S303, the electronic device can accurately obtain the first operating frequency, the second operating frequency, and the third operating frequency through a SWAP experiment, thereby improving the accuracy of the target coupling strength determined based on the first operating frequency, the second operating frequency, and the third operating frequency.

[0087] In an optional embodiment, when the above-described periodic quantum logic gate operation is a CZ gate operation, according to the above... Figure 2 The method shown in this application embodiment also provides a method for obtaining the correspondence. For example... Figure 4 As shown, Figure 4 This is a flowchart illustrating a method for obtaining correspondences provided in an embodiment of this application. The method includes the following steps.

[0088] Step S401: Based on the target coupling strength, according to multiple CZ gate operations on the first and second qubits under different frequency detuning conditions, obtain the first correspondence between the first detuning, the second detuning, and the leakage rate.

[0089] In this step, the electronic device can perform multiple CZ gate operations on the first qubit and the second qubit under the aforementioned target coupling strength. Each CZ gate operation corresponds to a different frequency detuning condition. That is, during each CZ gate operation, the electronic device can adjust the first detuning and the second detuning. The electronic device can jointly read out the quantum state after each CZ gate operation to obtain the first correspondence between the first detuning, the second detuning, and the leakage rate.

[0090] In an optional embodiment, the leakage rate described above can be represented by the excited state probability. For example, the leakage rate can be represented by the probability P of |11>. 11 The method of obtaining and representing the first correspondence is described below and will not be explained in detail here.

[0091] Step S402: Based on the target coupling strength, according to multiple Ramsey experiments on the first and second qubits under different frequency detuning conditions, obtain the second correspondence between the first detuning, the second detuning, and the preset condition phase. The free evolution process of each Ramsey experiment executes CZ gate operations on the first and second qubits.

[0092] In related techniques, a Ramsey experiment can include the following steps: initialization, a first π / 2 quantum logic gate operation, free evolution, a second π / 2 quantum logic gate operation, and quantum state readout. Initialization initializes the qubit to its ground state. The first π / 2 quantum logic gate operation applies a π / 2 pulse to one qubit (the target qubit), causing the quantum state to rotate from the ground state to the equatorial plane of the Bloch sphere. Free evolution allows the target qubit to evolve freely for a period without external driving, during which the quantum state rotates around the Z-axis in the equatorial plane of the Bloch sphere. The second π / 2 quantum logic gate operation applies a π / 2 pulse to the target qubit, rotating the quantum state back from the equatorial plane to the Z-axis. The quantum state readout measures the probability distribution of the quantum state in the ground and excited states. Throughout the Ramsey experiment, no driving pulse is applied to the other qubit (the bias qubit).

[0093] In this embodiment, the electronic device can perform multiple Ramsey experiments on the first and second qubits based on the aforementioned target coupling strength. During the free evolution of each Ramsey experiment, the first and second qubits perform CZ gate operations according to different detuning conditions, including first and second detuning. The electronic device can obtain a second correspondence between the first detuning, the second detuning, and the preset conditional phase based on multiple Ramsey experiments. The method of obtaining and representing the second correspondence is described below and will not be specifically explained here.

[0094] Steps S401-S402 above are a refinement of step S202 above.

[0095] Through the above steps S401-S402, the electronic device can obtain the first and second correspondences respectively in different ways according to the CZ gate operations on the first and second qubits. While ensuring the accuracy of the obtained first and second correspondences, it is convenient to determine the target detuning parameters in the later stage.

[0096] In an optional embodiment, according to the above... Figure 4 The method shown in this application embodiment also provides a method for obtaining a first correspondence. For example... Figure 5 As shown, Figure 5 This is a flowchart illustrating a first correspondence provided in an embodiment of this application. The method includes the following steps.

[0097] Step S501: Based on the target coupling strength, according to multiple CZ gate operations on the first and second qubits under different frequency detuning conditions, obtain the excited state probability under each frequency detuning condition. The excited state probability is used to indicate the leakage rate of the CZ gate operation.

[0098] In this step, the electronic device can perform joint readout based on the target coupling strength described above, according to the CZ gate operation performed under each detuning condition. For example, the electronic device can obtain the probability P of |00> corresponding to each detuning condition through joint readout. 00 The probability P of |01> 01 The probability P of |10> 10 The probability P of |11> 11 Electronic devices can obtain the probabilities of excited states under various detuning conditions, i.e., P. 11 .

[0099] In this embodiment, the aforementioned excited state modification is used to indicate the leakage rate of CZ gate operation. For example, the aforementioned excited state probability P 11 It is inversely proportional to the leakage rate. That is, the excited state probability P 11The larger the value, the smaller the leakage rate and the higher the excited state probability P. 11 The smaller the value, the greater the leakage rate.

[0100] Step S502: Based on the excitation state probability under each frequency detuning condition, generate a first change relationship diagram indicating the correspondence between the first detuning, the second detuning, and the excitation state probability.

[0101] In this step, for each frequency detuning condition, the excited state probability under that frequency detuning condition includes the correspondence between the first detuning, the second detuning, and the excited state probability corresponding to that frequency detuning condition. Therefore, the electronic device can generate a first transformation diagram indicating the correspondence based on the excited state probability under each frequency detuning condition, that is, based on the correspondence between the first detuning, the second detuning, and the excited state probability under each frequency detuning condition.

[0102] For ease of understanding, combined with Figure 6 Please provide an explanation. Figure 6 This is a schematic diagram of a transformation relationship provided in an embodiment of this application.

[0103] exist Figure 6 The diagram includes two transformation relationship diagrams. The transformation relationship diagram located in the upper part is the first transformation relationship diagram mentioned above. In the first transformation relationship diagram, the horizontal axis represents the first detuning, and the vertical axis represents the second detuning. The color corresponding to each coordinate point in the diagram represents the excitation state probability P under the first detuning and the second detuning at that coordinate point. 11 .

[0104] Steps S501-S502 above are a refinement of step S401 above.

[0105] Through the above steps S501-S502, the electronic device can use the excitation state probability corresponding to the CZ gate operation to indicate the leakage rate of the first and second qubits when performing the CZ gate operation. Thus, a first transformation relationship diagram is generated based on the excitation state probability under each frequency detuning condition. The diagram visually reflects the correspondence between the first detuning, the second detuning, and the excitation state probability, and indirectly reflects the correspondence between the first detuning, the second detuning, and the leakage rate, thereby facilitating the acquisition of the target detuning parameters in the later stage.

[0106] In an optional embodiment, according to the above... Figure 4 The method shown in this application embodiment also provides a second method for obtaining the correspondence. For example... Figure 7 As shown, Figure 7 This is a flowchart illustrating a second correspondence acquisition method provided in an embodiment of this application. The method includes the following steps.

[0107] Step S701: Based on the target coupling strength and different frequency detuning conditions, according to the multiple Ramsey experiments performed by the first and second qubits under the first experimental conditions, obtain the first phase corresponding to each detuning condition.

[0108] For ease of understanding, the acquisition of the first phase will be explained below using the first qubit as the bias qubit and the second qubit as the target qubit.

[0109] Under the aforementioned first experimental conditions, after initialization, during each Ramsey experiment, a π / 2 quantum logic gate operation is performed on the second qubit during both the first and second π / 2 quantum logic gate operations, i.e., a π / 2 pulse is applied. During the first π / 2 quantum logic gate operation, a π quantum logic gate operation is performed on the first qubit, i.e., a π pulse is applied. Furthermore, during free evolution, CZ gate operations are performed on both the first and second qubits, allowing the electronic device to acquire the first phase corresponding to each Ramsey experiment.

[0110] To facilitate understanding, let's take a Ramsey experiment as an example. Under the conditions of the first experiment, after the first manipulation using a π / 2 quantum logic gate, the quantum state is prepared as follows: After CZ gate operation under a certain frequency detuning condition, the quantum state is prepared to: in, The phase of |10> The phase is |11>. After the second π / 2 quantum logic gate manipulation, the read phase is the first phase phase1 mentioned above.

[0111] Step S702: Based on the target coupling strength and different frequency detuning conditions, according to the multiple Ramsey experiments performed by the first and second qubits under the second experimental conditions, obtain the second phase corresponding to each detuning condition; wherein, the difference between the first and second experimental conditions is that during the first π / 2 quantum logic gate operation of each Ramsey experiment, a π quantum logic gate operation is performed on the third qubit, and the third qubit is the qubit among the first and second qubits that did not perform the π / 2 quantum logic gate operation.

[0112] For ease of understanding, the following explanation will still use the first qubit as the bias qubit and the second qubit as the target qubit as an example to illustrate the acquisition of the second phase.

[0113] Under the second experimental conditions described above, after the initialization operation, during each Ramsey experiment, a π / 2 quantum logic gate operation is performed on the second qubit during the first and second π / 2 quantum logic gate operations, i.e., a π / 2 pulse is applied. Furthermore, during the free evolution, a CZ gate operation is performed on the first and second qubits, and the electronic device can acquire the second phase corresponding to each Ramsey experiment.

[0114] To facilitate understanding, let's take a Ramsey experiment as an example. Under the conditions of the second experiment described above, after the first manipulation using a π / 2 quantum logic gate, the quantum state is prepared as follows: After CZ gate operation under a certain frequency detuning condition, the quantum state is prepared to: Where e is the natural constant and i is the imaginary unit. The phase of |00> The phase is |01>. After the second π / 2 quantum logic gate manipulation, the read phase is the second phase phase2 mentioned above.

[0115] For steps S701 and S702 above, the experimental conditions for each Ramsey experiment are different. That is, the first experimental condition and the second experimental condition are different. Specifically, under the first experimental condition, a π pulse needs to be applied to the bias qubit during the first π / 2 quantum logic gate operation, while under the second experimental condition, it is not necessary to apply a π pulse to the bias qubit during the first π / 2 quantum logic gate operation. Apart from this, all other experimental conditions are the same.

[0116] Step S703: For each frequency detuning condition, calculate the difference between the first phase and the second phase under that frequency detuning condition to obtain the preset condition phase corresponding to that frequency detuning condition.

[0117] In an optional embodiment, for each frequency detuning condition, the electronic device can use the following formula to calculate the preset condition phase corresponding to that frequency detuning condition.

[0118]

[0119] Step S704: Based on the preset condition phase under each frequency detuning condition, generate a second transformation relationship diagram indicating the correspondence between the first detuning, the second detuning, and the preset condition phase.

[0120] In this step, for each frequency detuning condition, the preset condition phase under that frequency detuning condition contains the correspondence between the first detuning, the second detuning, and the preset condition phase corresponding to that frequency detuning condition. Therefore, the electronic device can generate a second transformation diagram indicating the correspondence based on the preset condition phase under each frequency detuning condition, that is, based on the correspondence between the first detuning, the second detuning, and the preset condition phase under each frequency detuning condition.

[0121] For ease of understanding, the above will still be used. Figure 6 Let's take an example to illustrate. Figure 6 The transformation relationship diagram located in the lower half is the second transformation relationship diagram mentioned above. In the second transformation relationship diagram, the horizontal axis represents the first detuning, and the vertical axis represents the second detuning. The color corresponding to each coordinate point in the diagram indicates the preset condition phase under the first and second detunings, i.e.

[0122] In an optional embodiment, when generating the first and second transformation relationship diagrams, to facilitate the subsequent acquisition of the target detuning parameters, the same frequency detuning condition can be used, i.e., as follows: Figure 6 The first and second transformation relationship diagrams shown include the same horizontal and vertical axes.

[0123] Steps S701-S704 above are a refinement of step S402 above.

[0124] Through steps S701-S704 above, the electronic device can obtain the preset condition phase under different frequency detuning conditions through the Ramsey experiment, thereby intuitively reflecting the correspondence between the first detuning, the second detuning, and the preset condition phase in the form of an image, which facilitates the acquisition of the target detuning parameters in the later stage.

[0125] In an optional embodiment, according to the above... Figure 2 , Figure 4 , Figure 5 and Figure 7 The method shown in this application embodiment also provides a method for obtaining target detuning parameters. For example... Figure 8 As shown, Figure 8 This is a flowchart illustrating a method for obtaining target detuning parameters provided in an embodiment of this application. The method includes the following steps.

[0126] Step S801: Determine all first coordinate points with a preset condition phase of π in the second transformation relationship diagram.

[0127] In the embodiments of this application, the above-mentioned periodic quantum logic gate operations need to satisfy leakage conditions and phase conditions. For example, the leakage conditions and phase conditions that the CZ gate needs to satisfy are: L = 0. At this point, the phase of the aforementioned target is π.

[0128] Electronic devices via the above Figure 5 and Figure 7 The method shown above is used to obtain the above-mentioned... Figure 6 After seeing the transformation diagram shown, the electronic device can determine all coordinate points (denoted as the first coordinate points) that satisfy the phase condition in the second transformation diagram. That is, all coordinate points in the second transformation diagram where the condition phase is π are determined as the first coordinate points.

[0129] In one alternative embodiment, such as Figure 6 As shown, the electronic device can draw the contour line corresponding to phase π in the second transformation diagram based on the color corresponding to phase π on the right side of the second transformation diagram. Figure 6 Curve 601. All coordinate points on curve 601 are the first coordinate points mentioned above.

[0130] In this embodiment, only the CZ gate operation of the periodic quantum logic gate is used as an example for explanation. The target phase differs for different periodic quantum logic gate operations. For example, when the periodic quantum logic gate operation is the CPhase described above, the target phase can be any phase. Here, no specific limitation is made on the target phase.

[0131] Step S802: Based on the first detuning and second detuning corresponding to each first coordinate point, determine the second coordinate point that matches each first coordinate point in the first transformation relationship diagram.

[0132] In this step, after determining the first coordinate point, the electronic device can map each first coordinate point to the first transformation relationship diagram according to the first detuning and second detuning corresponding to each first coordinate point, so as to obtain the second coordinate point that matches each first coordinate point.

[0133] The first and second coordinate points mentioned above correspond to the same first and second detuning.

[0134] In an optional embodiment, if the abscissa and ordinate of the first transformation relationship diagram and the second transformation relationship diagram are the same, then when determining the second coordinate point, the electronic device can directly determine the contour line that matches the curve 601 in the second transformation relationship diagram in the first transformation relationship diagram, and each coordinate point on the contour line is the second coordinate point.

[0135] Step S803: Based on the excited state probability corresponding to each second coordinate point, select the second coordinate point with the highest excited state probability as the target coordinate point.

[0136] For each second coordinate point, there exists a corresponding excited state probability in the first transformation relationship diagram described above. The electronic device can select the second coordinate point that satisfies the above leakage conditions as the target coordinate point. That is, the second coordinate point with the highest excited state probability is selected as the target coordinate point.

[0137] For example, in the above Figure 6 In the first transformation diagram shown, coordinate point 602 is the second coordinate point with the highest excited state probability among all second coordinate points. That is, coordinate point 602 is the target coordinate point.

[0138] In the above Figure 6 In the first transformation diagram shown, coordinate point 603 represents the frequency detuning determined using correlation techniques. Comparing coordinate points 602 and 603, the leakage rate at coordinate point 602 is significantly lower than that at coordinate point 603, thereby enhancing the periodicity of the control waveform.

[0139] Step S804: Determine the first and second detunings corresponding to the target coordinate points as the target detuning parameters.

[0140] In this step, each coordinate point in the first transformation relationship diagram has a corresponding first detuning, second detuning, and excited state probability. After determining the target coordinate point, the electronic device can determine the first and second detunings corresponding to that target coordinate point as the target detuning parameters.

[0141] Steps S801-S804 above are a refinement of step S203 above.

[0142] Through steps S801-S804, the electronic device can directly determine the first and second detunings that satisfy the leakage and phase conditions based on the first and second transformation relationship diagrams. This ensures the accuracy of the determined detuning parameters while simplifying the process of obtaining the frequency detuning parameters in the parameter space degrees of freedom, thus providing a guarantee for the execution of subsequent periodic quantum logic gate operations.

[0143] In the above Figure 8 The method described herein is illustrated by first determining the first and second detunings that satisfy the phase condition, and then determining the target detuning parameter that satisfies the leakage condition from the determined first and second detunings. Alternatively, the electronic device may first determine the first and second detunings that satisfy the leakage condition, and then determine the target detuning parameter for the phase condition from the determined first and second detunings. Here, the method for determining the target detuning parameter is not specifically limited.

[0144] In an optional embodiment, according to the above... Figure 2The method shown in this application embodiment also provides a method for determining the degrees of freedom in the parameter space. For example... Figure 9 As shown, Figure 9 This is a schematic diagram of a second flowchart illustrating the method for determining the degrees of freedom in the parameter space provided in an embodiment of this application. Figure 9 The method shown has been augmented with the following step, namely step S204.

[0145] Step S204: Based on the target coupling strength and target detuning parameters, perform periodic quantum logic gate operations using the first and second qubits.

[0146] In this step, the electronic device can perform periodic quantum logic gate operations, such as the CZ gate operation described above, using the first and second qubits within the target coupling strength and target detuning parameter space, i.e., S′={(g,Δ1,Δ2)}. Here, g is the target coupling strength, Detune1 is the first detuning parameter in the target detuning parameters, and Δ2 is the second detuning parameter in the target detuning parameters.

[0147] For ease of understanding, combined with Figure 10 Let's take an example to illustrate. Figure 10 This is a schematic diagram illustrating the CZ gate operation fidelity provided in an embodiment of this application. The electronic device is based on S={(g,Δ)} determined in related technologies and S′={(g,Δ1,Δ2)} determined in this embodiment of the application, in six pairs of qubits, i.e. Figure 10 The CZ gate operation is performed on G1-G6 as shown, and the fidelity of the CZ gate operation is obtained. The blue part is the fidelity of the CZ gate operation obtained in the parameter space S={(g,Δ)}, and the red part is the fidelity of the CZ gate operation obtained in the parameter space S′={(g,Δ1,Δ2)}.

[0148] exist Figure 10 In this application, the fidelity of CZ gate operations performed using the embodiments of this application is significantly higher than that performed using related technologies. Specifically, the average fidelity obtained using related technologies for CZ gate operations is approximately 97.10%, while the average fidelity obtained using the embodiments of this application is approximately 97.78%. Comparatively, the fidelity of CZ gate operations performed using the embodiments of this application is significantly improved, effectively avoiding the impact of STDs.

[0149] Through the above step S204, the electronic device can execute periodic quantum logic gates based on the determined target coupling strength and target detuning parameters, avoiding the influence of STD on the operation of periodic quantum logic gates and improving the fidelity of quantum computing.

[0150] In an optional embodiment, according to the above... Figure 9The method shown in this application embodiment also provides a method for determining the degrees of freedom in the parameter space. For example... Figure 11 As shown, Figure 11 This is a schematic diagram of a third method for determining the degrees of freedom in the parameter space provided in an embodiment of this application. The method includes the following steps.

[0151] Step S1101: Calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. The tunable coupler is used to couple the first and second qubits.

[0152] Step S1102: Based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, obtain the first correspondence between frequency detuning and leakage rate, and obtain the second correspondence between frequency detuning and preset condition phase. Each frequency detuning condition includes the first detuning and the second detuning. The first detuning and the second detuning are the frequency differences corresponding to the control waveforms of the periodic quantum logic gate operations in different time periods within the same time period.

[0153] Step S1103: Based on the first correspondence and the second correspondence, obtain the first detuning and the second detuning with the lowest leakage rate under the target phase as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0154] The steps S1101-S1103 described above are the same as the steps S201-S203 described above.

[0155] Step S1104: Based on the NM optimization algorithm and cross-entropy characterization method, the target coupling strength and target detuning parameters are optimized to obtain the optimized target parameters.

[0156] In this step, after obtaining the target coupling strength and target detuning parameters, the electronic device can use an optimization algorithm, combined with the fidelity during the execution of the periodic quantum logic gate, to optimize the first and second detunings in the target coupling strength and target detuning parameters, to obtain the optimized target coupling strength, first detuning, and second detuning (denoted as the optimized target parameters). The optimization process can be referred to in related technologies for optimization methods, and will not be specifically described here.

[0157] In this embodiment, only the Nelder-Mead (NM) optimization algorithm and the Cross-Entropy Benchmarking (XEB) algorithm are used as examples for illustration. The NM algorithm is an algorithm for finding local minima of a multivariate function. Its advantage is that it does not require the function to be differentiable and can converge to a local minimum relatively quickly. Besides this, electronic devices can also employ other optimization algorithms and fidelity calculation methods to optimize the target coupling strength and target detuning parameters. Here, the algorithms used in the above optimization process are not specifically limited.

[0158] Step S1105: Based on the optimized target parameters, perform periodic quantum logic gate operations using the first and second qubits.

[0159] Through the above steps S1104-S1105, after obtaining the degrees of freedom of the control waveform in the parameter space, namely the target coupling strength and the target detuning parameter, the electronic device can effectively improve the accuracy of the optimized target parameters by optimizing the target coupling strength and the target detuning parameter, thereby improving the fidelity of performing periodic quantum logic gate operations based on the optimized target parameters.

[0160] In an optional embodiment, according to the above... Figure 9 The method shown in this application embodiment also provides a method for determining the degrees of freedom in the parameter space. For example... Figure 12 As shown, Figure 12 This is a schematic diagram of a fourth method for determining the degrees of freedom in the parameter space provided in an embodiment of this application. The method includes the following steps.

[0161] Step S1201: Calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler at a preset gate length. The tunable coupler is used to couple the first and second qubits.

[0162] Step S1202: Based on the target coupling strength, according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, obtain the first correspondence between frequency detuning and leakage rate, and obtain the second correspondence between frequency detuning and preset condition phase. Each frequency detuning condition includes the first detuning and the second detuning. The first detuning and the second detuning are the frequency differences corresponding to the control waveforms of the periodic quantum logic gate operations in different time periods within the same time period.

[0163] Step S1203: Based on the first correspondence and the second correspondence, obtain the first detuning and the second detuning with the lowest leakage rate under the target phase as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0164] The steps S1201-S1203 described above are the same as those S201-S203 described above.

[0165] Step S1204: Based on the target detuning parameters, a preset number of third detunings are generated using a machine learning algorithm.

[0166] In this step, after determining the target mistuning parameters, the electronic device can generate other mistunings (denoted as the third mistuning) based on the first and second mistunings in the target mistuning parameters using a machine learning algorithm. The number of third mistunings can be one or more (i.e., the preset number mentioned above). The method for obtaining the third mistunings can be referred to the generation method in related technologies, and will not be specifically described here.

[0167] The aforementioned machine learning algorithms may include heuristic rule-based optimization algorithms (Nelder-Mead, NM), differential evolution (DE), particle swarm optimization (PSO), etc. Here, no specific limitation is made on the aforementioned machine learning algorithms.

[0168] Step S1205: Based on the target coupling strength, target detuning parameter, and third detuning, perform periodic quantum logic gate operations using the first and second qubits.

[0169] Through the above steps S1204-S1205, the electronic device can increase the number of frequency detunings based on the first and second detunings in the determined target detuning parameters using a machine learning algorithm, thereby increasing the number of degrees of freedom in the parameter space. To a certain extent, this can further improve the fidelity of the operation of periodic quantum logic gates.

[0170] Based on the same inventive concept, and according to the parameter space degree of freedom determination method provided in the above embodiments of this application, this application also provides a parameter space degree of freedom determination device. For example... Figure 13 As shown, Figure 13 This is a schematic diagram of a parameter space degree-of-freedom determination device provided in an embodiment of this application. The device includes the following modules.

[0171] The calculation module 1301 is used to calculate the target coupling strength between the first quantum bit and the second quantum bit based on the first operating frequency and the second operating frequency corresponding to the first quantum bit and the second quantum bit when the frequency detuning is 0, and the third operating frequency of the tunable coupler under a preset gate length. The tunable coupler is used to couple the first quantum bit and the second quantum bit.

[0172] The first acquisition module 1302 is used to acquire, based on the target coupling strength, the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, the first correspondence between frequency detuning and leakage rate, and the second correspondence between frequency detuning and preset condition phase. Each frequency detuning condition includes the first detuning and the second detuning, which are the frequency differences of the control waveforms of the periodic quantum logic gate operations within the same time period at different time periods.

[0173] The second acquisition module 1303 is used to acquire the first detuning and the second detuning with the lowest leakage rate under the target phase based on the first correspondence and the second correspondence, as target detuning parameters, wherein the target coupling strength and the target detuning parameters are the degrees of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space.

[0174] Optionally, the above-mentioned calculation module 1301 may include:

[0175] The first determining submodule is used to determine the operating frequency corresponding to the resonance of the first and second qubits through a SWAP experiment on the first and second qubits, thereby obtaining the first and second operating frequencies.

[0176] The second determining submodule is used to determine the third operating frequency of the tunable coupler at a preset gate length by performing a SWAP experiment on the first and second qubits when the voltage on the tunable coupler changes.

[0177] The computational submodule is used to calculate the target coupling strength between the first qubit and the second qubit based on the first operating frequency, the second operating frequency, and the third operating frequency.

[0178] Optionally, the above-mentioned computational submodule can be used to calculate the target coupling strength between the first quantum bit and the second quantum bit using the following formula;

[0179]

[0180] Where g is the target coupling strength, w1 is the first operating frequency, w2 is the second operating frequency, and w c For the third operating frequency, 1 / Δ = (1 / Δ1 + 1 / Δ2) / 2, Δ iThe frequency difference between the quantum bit and the tunable coupler. C 1c C is the coupling capacitance between the first quantum bit and the tunable coupler. 2c C is the coupling capacitance between the second qubit and the tunable coupler. 12 C is the coupling capacitance between the first and second qubits. c The capacitor is for the adjustable coupler. Σ j =ω j +ω c C1 is the sum of the frequencies of the qubit and the tunable coupler, C2 is the capacitance of the first qubit, and C2 is the capacitance of the second qubit.

[0181] Optionally, the first acquisition module 1302 described above may include:

[0182] The first acquisition submodule is used to acquire, based on the target coupling strength, the first correspondence between the first detuning, the second detuning and the leakage rate, according to multiple CZ gate operations on the first and second qubits under different frequency detuning conditions, if the periodic quantum logic gate operation is a CZ gate operation.

[0183] The second acquisition submodule is used to acquire the second correspondence between the first detuning, the second detuning, and the preset condition phase based on the target coupling strength and multiple Ramsey experiments on the first and second qubits under different frequency detuning conditions. Each free evolution process of the Ramsey experiment executes CZ gate operations on the first and second qubits.

[0184] Optionally, the first acquisition submodule described above can be specifically used to acquire the excited state probability under each frequency detuning condition based on the target coupling strength and multiple CZ gate operations on the first and second qubits under different frequency detuning conditions. The excited state probability is used to indicate the leakage rate of the CZ gate operation.

[0185] Based on the excitation state probability under each frequency detuning condition, a first change relationship diagram is generated indicating the correspondence between the first detuning, the second detuning, and the excitation state probability.

[0186] Optionally, the second acquisition submodule described above can be used to acquire the first phase corresponding to each detuning condition based on the target coupling strength and different frequency detuning conditions, according to multiple Ramsey experiments performed by the first and second qubits under the first experimental conditions.

[0187] Based on the target coupling strength and different frequency detuning conditions, the second phase corresponding to each detuning condition is obtained according to multiple Ramsey experiments performed by the first and second qubits under the second experimental conditions. The difference between the first and second experimental conditions is that during the first π / 2 quantum logic gate operation of each Ramsey experiment, a π quantum logic gate operation is performed on the third qubit, and the third qubit is the qubit in the first and second qubits that did not perform the π / 2 quantum logic gate operation.

[0188] For each frequency detuning condition, calculate the difference between the first phase and the second phase under that frequency detuning condition to obtain the corresponding preset condition phase under that frequency detuning condition.

[0189] Based on the preset condition phase under each frequency detuning condition, a second transformation relationship diagram is generated that indicates the correspondence between the first detuning, the second detuning, and the preset condition phase.

[0190] Optionally, the second acquisition module 1303 can be used to determine all first coordinate points with a preset condition phase of π in the second transformation relationship diagram;

[0191] Based on the first and second detuning corresponding to each first coordinate point, determine the second coordinate point that matches each first coordinate point in the first transformation relationship diagram;

[0192] Based on the excited state probability corresponding to each second coordinate point, the second coordinate point with the highest excited state probability is selected as the target coordinate point;

[0193] The first and second detunings corresponding to the target coordinate points are determined as the target detuning parameters.

[0194] Optionally, the above-mentioned parameter space degree of freedom determination device may further include:

[0195] The execution module is used to perform periodic quantum logic gate operations using the first and second qubits based on the target coupling strength and the target detuning parameters.

[0196] Optionally, the above-mentioned parameter space degree of freedom determination device may further include:

[0197] The optimization module is used to optimize the target coupling strength and target detuning parameters based on the NM optimization algorithm and the cross-entropy characterization method before performing periodic quantum logic gate operations using the first and second qubits based on the target coupling strength and target detuning parameters, so as to obtain the optimized target parameters.

[0198] Specifically, the aforementioned execution module can be used to perform periodic quantum logic gate operations using the first and second qubits based on optimized target parameters.

[0199] Optionally, the above-mentioned parameter space degree of freedom determination device may further include:

[0200] The generation module is used to generate a preset number of third detunes based on the target detuning parameters and using a machine learning algorithm before performing periodic quantum logic gate operations using the first and second qubits based on the target coupling strength and target detuning parameters.

[0201] Specifically, the aforementioned execution module can be used to perform periodic quantum logic gate operations using the first and second qubits based on the target coupling strength, the target detuning parameter, and the third detuning.

[0202] The apparatus provided in this application embodiment can calculate the target coupling strength between the first and second qubits based on the first and second operating frequencies corresponding to the first and second qubits when the frequency detuning is 0, and the third operating frequency of the tunable coupler under a preset gate length. Based on the target coupling strength, and according to the periodic quantum logic gate operations on the first and second qubits under different frequency detuning conditions, a first correspondence between frequency detuning and leakage rate, and a second correspondence between frequency detuning and qubit phase are obtained. Thus, the target detuning parameters, namely the first detuning and the second detuning, are determined based on the first and second correspondences.

[0203] The presence of STDs (Standard Degrees of Freedom) causes the number of degrees of freedom during periodic quantum logic gate operations to be less than the number of constraints, thus affecting the quantum computing results. Therefore, compared to related technologies that only use coupling strength and one frequency detuning as the degree of freedom of the control waveform corresponding to the periodic quantum logic gate operation in the parameter space, the embodiments of this application introduce two detunings during the determination of the degree of freedom in the parameter space, namely the first detuning and the second detuning. This increases the number of degrees of freedom in the parameter space during the periodic quantum logic gate operation to a state that matches the constraints during the quantum logic gate operation, effectively avoiding the influence of STDs on the periodic quantum logic gate operation, that is, avoiding the influence of residual short-timescale distortions on the flux control line on the quantum computing process, thereby improving the fidelity of quantum computing.

[0204] In addition, the first and second detunings in the parameter space degrees of freedom are the frequency detunings corresponding to the lowest leakage rate under the target phase. This ensures that the determined first and second detunings can satisfy the leakage and phase conditions corresponding to the control waveform, guaranteeing the accuracy of the determined target detuning parameters and thus improving the fidelity of quantum computing.

[0205] Based on the same inventive concept, and according to the parameter space degree of freedom determination method provided in the above embodiments of this application, this application also provides an electronic device, such as... Figure 14 As shown, it includes a processor 1401, a communication interface 1402, a memory 1403, and a communication bus 1404, wherein the processor 1401, the communication interface 1402, and the memory 1403 communicate with each other through the communication bus 1404.

[0206] Memory 1403 is used to store computer programs;

[0207] When the processor 1401 executes the program stored in the memory 1403, it implements the steps of the parameter space degree of freedom determination method described above.

[0208] The communication bus mentioned in the above electronic devices can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. This communication bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used to represent it in the diagram, but this does not mean that there is only one bus or one type of bus.

[0209] The communication interface is used for communication between the aforementioned electronic devices and other devices.

[0210] The memory may include random access memory (RAM) or non-volatile memory (NVM), such as at least one disk storage device. Optionally, the memory may also be at least one storage device located remotely from the aforementioned processor.

[0211] The processors mentioned above can be general-purpose processors, including central processing units (CPUs), network processors (NPs), etc.; they can also be digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0212] Based on the same inventive concept, and according to the parameter space degree of freedom determination method provided in the above-described embodiments of this application, this application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of any of the above-described parameter space degree of freedom determination methods.

[0213] Based on the same inventive concept, and according to the parameter space degree of freedom determination method provided in the above embodiments of this application, this application also provides a computer program product containing instructions, which, when run on a computer, causes the computer to execute any of the parameter space degree of freedom methods in the above embodiments.

[0214] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid state disk (SSD)).

[0215] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0216] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, embodiments such as apparatuses, electronic devices, computer-readable storage media, and computer program products are basically similar to the method embodiments, and therefore the descriptions are relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0217] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for determining the degrees of freedom in a parameter space, characterized in that, The method comprises: According to the first working frequency and the second working frequency corresponding to the first quantum bit and the second quantum bit when the frequency mismatch is 0, and the third working frequency of the adjustable coupler under a preset gate length, the target coupling strength between the first quantum bit and the second quantum bit is calculated, and the adjustable coupler is used to couple the first quantum bit and the second quantum bit; Based on the target coupling strength, the first corresponding relationship between the frequency mismatch and the leakage rate is obtained according to the periodic quantum logic gate operation on the first quantum bit and the second quantum bit under different frequency mismatch conditions, and the second corresponding relationship between the frequency mismatch and the preset condition phase is obtained, wherein each frequency mismatch condition includes a first mismatch and a second mismatch, and the first mismatch and the second mismatch are the frequency difference corresponding to the control waveform of the periodic quantum logic gate operation in different time periods in the same time period. Based on the first corresponding relationship and the second corresponding relationship, the first mismatch and the second mismatch corresponding to the lowest leakage rate under the target phase are obtained as target mismatch parameters, wherein the target coupling strength and the target mismatch parameter are the degrees of freedom of the corresponding control waveform of the periodic quantum logic gate operation in the parameter space.

2. The method of claim 1, wherein, The step of calculating the target coupling strength between the first quantum bit and the second quantum bit according to the first working frequency and the second working frequency corresponding to the first quantum bit and the second quantum bit when the frequency mismatch is 0, and the third working frequency of the adjustable coupler under a preset gate length, comprises: The first working frequency and the second working frequency corresponding to the first quantum bit and the second quantum bit are determined through the exchange SWAP experiment on the first quantum bit and the second quantum bit, and the first working frequency and the second working frequency are obtained; In the case that the voltage of the adjustable coupler changes, the third working frequency of the adjustable coupler under the preset gate length is determined through the SWAP experiment on the first quantum bit and the second quantum bit; Based on the first working frequency, the second working frequency and the third working frequency, the target coupling strength between the first quantum bit and the second quantum bit is calculated.

3. The method of claim 2, wherein, The step of calculating the target coupling strength between the first quantum bit and the second quantum bit based on the first working frequency, the second working frequency and the third working frequency, comprises: The target coupling strength between the first quantum bit and the second quantum is calculated by using the following formula: Where g is the target coupling strength, w1 is the first operating frequency, w2 is the second operating frequency, and w c For the third operating frequency, 1 / Δ = (1 / Δ1 + 1 / Δ2) / 2, Δ i The frequency difference between the quantum bit and the tunable coupler. C 1c C is the coupling capacitance between the first quantum bit and the tunable coupler. 2c C is the coupling capacitance between the second quantum bit and the tunable coupler. 12 C is the coupling capacitance between the first qubit and the second qubit. c The capacitance of the adjustable coupler. Σ j =ω j +ω c C1 is the sum of the frequencies corresponding to the qubit and the tunable coupler, C2 is the capacitance of the first qubit, and C2 is the capacitance of the second qubit.

4. The method of claim 1, wherein, If the periodic quantum logic gate operation is a CZ gate operation, the step of obtaining the first corresponding relationship between the frequency mismatch and the leakage rate, and the second corresponding relationship between the frequency mismatch and the preset condition phase based on the target coupling strength according to the periodic quantum logic gate operation on the first quantum bit and the second quantum bit under different frequency mismatch conditions, comprises: Based on the target coupling strength, the first corresponding relationship between the first mismatch, the second mismatch and the leakage rate is obtained according to the multiple CZ gate operations on the first quantum bit and the second quantum bit under different frequency mismatch conditions; According to a plurality of Ramsey experiments on the first quantum bit and the second quantum bit under different frequency detuning conditions, a second corresponding relationship between the first detuning, the second detuning and a preset condition phase is obtained based on the target coupling strength, and a free evolution process of each Ramsey experiment performs a CZ gate operation on the first quantum bit and the second quantum bit.

5. The method of claim 4, wherein, The step of obtaining a first corresponding relationship between the first detuning, the second detuning and a leakage rate based on a plurality of CZ gate operations on the first quantum bit and the second quantum bit under different frequency detuning conditions based on the target coupling strength comprises: According to a plurality of CZ gate operations on the first quantum bit and the second quantum bit under different frequency detuning conditions based on the target coupling strength, an excited state probability under each frequency detuning condition is obtained, and the excited state probability is used to indicate a leakage rate of the CZ gate operation. According to the excited state probability under each frequency detuning condition, a first change relationship diagram indicating the corresponding relationship between the first detuning, the second detuning and the excited state probability is generated.

6. The method of claim 5, wherein, The step of obtaining a second corresponding relationship between the first detuning, the second detuning and a preset condition phase based on a plurality of Ramsey experiments on the first quantum bit and the second quantum bit under different frequency detuning conditions based on the target coupling strength comprises: According to a plurality of Ramsey experiments performed by the first quantum bit and the second quantum bit under a first experimental condition, a first phase corresponding to each detuning condition is obtained based on the target coupling strength and different frequency detuning conditions. According to a plurality of Ramsey experiments performed by the first quantum bit and the second quantum bit under a second experimental condition, a second phase corresponding to each detuning condition is obtained based on the target coupling strength and different frequency detuning conditions, wherein the first experimental condition and the second experimental condition differ in that a π quantum logic gate operation is performed on a third quantum bit during a first π / 2 quantum logic gate operation of each Ramsey experiment, and the third quantum bit is a quantum bit that does not perform a π / 2 quantum logic gate operation among the first quantum bit and the second quantum bit. For each frequency detuning condition, a difference between the first phase and the second phase under the frequency detuning condition is calculated to obtain a corresponding preset condition phase under the frequency detuning condition. Based on the preset condition phases under the frequency detuning conditions, a second transformation relationship diagram indicating the corresponding relationship between the first detuning, the second detuning and the preset condition phase is generated.

7. The method of claim 6, wherein, The step of obtaining, based on the first corresponding relationship and the second corresponding relationship, the first detuning and the second detuning corresponding to the lowest leakage rate under the target phase as the target detuning parameter comprises: All first coordinate points in the second transformation relationship diagram are determined when the preset condition phase is π. According to the first detuning and the second detuning corresponding to each first coordinate point, second coordinate points matched with the first coordinate points are determined in the first transformation relationship diagram. According to the excitation state probability corresponding to each second coordinate point, a second coordinate point with the maximum excitation state probability is selected as a target coordinate point; The first detuning and the second detuning corresponding to the target coordinate point are determined as target detuning parameters.

8. The method according to any one of claims 1 to 7, characterized in that, The method further includes: Based on the target coupling strength and the target detuning parameters, the first quantum bit and the second quantum bit are used to perform the periodic quantum logic gate operation.

9. The method of claim 8, wherein, Before the first quantum bit and the second quantum bit are used to perform the periodic quantum logic gate operation based on the target coupling strength and the target detuning parameters, the method further includes: Based on the NM optimization algorithm and the cross-entropy representation method, the target coupling strength and the target detuning parameters are optimized to obtain optimized target parameters; The step of using the first quantum bit and the second quantum bit to perform the periodic quantum logic gate operation based on the target coupling strength and the target detuning parameters includes: Based on the optimized target parameters, the first quantum bit and the second quantum bit are used to perform the periodic quantum logic gate operation.

10. The method of claim 8, wherein, Before the first quantum bit and the second quantum bit are used to perform the periodic quantum logic gate operation based on the target coupling strength and the target detuning parameters, the method further includes: Based on the target detuning parameters, a preset number of third detunings are generated using a machine learning algorithm; The step of using the first quantum bit and the second quantum bit to perform the periodic quantum logic gate operation based on the target coupling strength and the target detuning parameters includes: Based on the target coupling strength, the target detuning parameters and the third detunings, the first quantum bit and the second quantum bit are used to perform the periodic quantum logic gate operation.

11. A parameter space degree of freedom determination apparatus characterized by comprising: The device includes: A calculation module is configured to calculate a target coupling strength between a first quantum bit and a second quantum bit based on a first operating frequency and a second operating frequency corresponding to the first quantum bit and the second quantum bit when a frequency detuning is 0, and a third operating frequency of an adjustable coupler under a preset gate length, the adjustable coupler being configured to couple the first quantum bit and the second quantum bit; A first acquisition module is configured to acquire a first correspondence relationship between frequency detuning and leakage rate and a second correspondence relationship between frequency detuning and a preset condition phase based on the target coupling strength and periodic quantum logic gate operations on the first quantum bit and the second quantum bit under different frequency detuning conditions, each frequency detuning condition including a first detuning and a second detuning, the first detuning and the second detuning being frequency differences corresponding to different time periods of a control waveform of the periodic quantum logic gate operation in a same time period; A second acquisition module is configured to acquire, based on the first correspondence relationship and the second correspondence relationship, a first detuning and a second detuning corresponding to the lowest leakage rate under a target phase as target detuning parameters, wherein the target coupling strength and the target detuning parameters are degrees of freedom of a control waveform of the periodic quantum logic gate operation in a parameter space.

12. An electronic device, comprising: The computer readable storage medium stores a computer program, and the computer program is executed by the processor to implement the method steps of any one of claims 1-10. The computer readable storage medium stores a computer program, and the computer program is executed by the processor to implement the method steps of any one of claims 1-10. The computer readable storage medium stores a computer program, and the computer program is executed by the processor to implement the method steps of any one of claims 1-10.

13. A computer-readable storage medium, characterized in that, ​

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