Construction method of excitation operator in variable component sub-feature solicitation algorithm

Abstract

The invention provides a construction method of an excitation operator in a variable component child solicitation algorithm, and the construction method of the excitation operator in the variable component child solicitation algorithm comprises the following steps: carrying out the base transformation of a CRY gate, and constructing a quantum circuit of a single excitation operator; a quantum circuit of a double-excitation operator is constructed by performing base transformation on a C3RY gate. According to the technical scheme, the quantum circuit of the single excitation operator is constructed by performing base transformation on the CRY gate; the C3RY gate is subjected to base transformation, a quantum circuit of a double-excitation operator is constructed, the use number of CNOT gates is reduced, and the depth of the quantum circuit is reduced.

Description

Background Art

[0002] The chemical properties of matter are closely related to the energy levels of molecules. For example, the prediction of chemical reaction rates needs to be based on the ground state energy levels of molecules, so the accurate calculation of molecular energy levels is a very important task. In classical computing mode, the energy levels of molecules can be accurately solved using the Full Configuration Interaction (FCI) algorithm, but the computational cost of this algorithm increases exponentially with the increase in molecular size, so it is not suitable for large molecules. However, this problem can be naturally solved on quantum computers built based on quantum mechanics.

[0003] The first quantum algorithm that can be used to solve the energy level problem of the molecular Hamiltonian is the Quantum Phase Estimating (QPE) algorithm. Compared with classical algorithms, QPE can provide exponential acceleration. However, the quantum hardware conditions required by QPE, such as error correction mechanism and long coherence time, are difficult to meet with the current Noisy Intermediate-Scale Quantum (NISQ) devices.

[0004] Recently, the variational quantum eigensolver (VQE) algorithm using a quantum-classical hybrid architecture has attracted widespread attention. In the VQE algorithm, in order to provide a quantum state that is easy to prepare and as close to the ground state as possible as the beginning of the algorithm, the Hatree-Fock state |HF> is generally used as a reference state The Hatree-Fock state |HF> assumes that the electrons of the molecule are all in the lowest energy orbitals, which not only provides a good initial approximation for the subsequent optimization process, but also provides the characteristics of the molecule's electron number, spin, and point group symmetry. The population distribution of the Hatree-Fock state will then be adjusted by the proposed circuit to generate a trial state for obtaining the ground state energy through measurement.

[0005] The design of the proposed circuit is the core of the VQE algorithm. Generally speaking, the construction idea of ​​the proposed circuit of the VQE algorithm comes from the imitation of the classic coupled cluster (CC) algorithm. The goal of the CC algorithm is to obtain the trial state by applying the exponential cluster operator to the trial state, that is, Where T is the cluster operator, which is composed of excitation operators of different orders and is used to adjust the population distribution of the reference state. The cluster operator T contains parameters to be optimized, and the variational method can be used to minimize the energy expectation value, so as to eventually find the ground state. Different cluster operators T correspond to different hypothetical structures. In order to reduce the amount of calculation, the cluster operator T generally only retains single excitation operators and double excitation operators, which is called the CCSD method. In addition, in order to solve the unitary problem of the exponential cluster operator in order to construct it as a quantum circuit, the cluster operator is generally redesigned as the anti-Hermitian cluster operator S = TT + , the corresponding new exponential cluster operator is e S =e T-T+ is a unitary operator, so the algorithm is called UCCSD.

[0006] The anti-Hermitian cluster operator S is still composed of a single excitation operator and a double excitation operator, and is a fermion operator. To construct the corresponding quantum circuit, the currently commonly used method is to use the Jordan-Wigner [1] , Parity basis [2] or Bravyi-Kitaev [3] The excitation operator is converted into a Pauli string by using the transformations above, and then into a quantum circuit after taking the imaginary part. The number of CNOT gates used for these three transformations depends on the specific form of the excitation operator. For a single excitation operator, the minimum is 4, 2, 2, and the maximum is unlimited; for a double excitation operator, the minimum is 48, 32, 32, and the maximum is also unlimited. Recently, the Qubit-Excitation [4] For the transformation, a fixed number of CNOT gates can be used, which is 4 and 48 for single and double excitation operators respectively. Compared with the previous three transformations, the average number is the smallest.

[0007] In summary, the implementation of the VQE algorithm requires the transformation of fermion excitation operators to construct quantum circuits. Existing transformation methods, such as Jordan-Wigner, Parity basis, Bravyi-Kitaev, and Qubit-Excitation, all convert the excitation operator into a Pauli string first, and then convert the Pauli string into a quantum circuit. Although this goal can be achieved, the number of CNOT gates used is large, resulting in a large depth of the quantum circuit. For current NISQ devices, affected by various noises and operational errors, the shallower the depth of the quantum circuit (the fewer CNOT gates used), the easier it is to obtain high-quality calculation results. Therefore, designing a better excitation operator transformation method is a very important research direction.

[0008] References:

[0009] [1]Pascual Jordan and Eugene Paul Wigner. the Pauli's Springer, 1993.

[0010] [2] Andrew Tranter, Sarah Sofia, Jake Seeley, Michael Kaicher, Jarrod McClean, Ryan Babbush, Peter V Coveney, Florian Mintert, Frank Wilhelm, and Peter J Love. The bravyi-kitaev transformation: Properties and applications.

[0011] International Journal of Quantum Chemistry, 115(19): 1431 - 1441, 2015.

[0012] [3] Sergey B Bravyi and Alexei Yu Kitaev. Fermionic quantum computation. Annals of Physics, 298(1): 210 - 226, 2002.

[0013] [4] Yordan S Yordanov, Vasileios Armaos, Crispin HW Barnes, and David RM Arvidsson-Shukur. Qubit-excitation-based adaptive variational quantum eigensolver. Communications Physics, 4(1): 228, 2021.

[0014] [5] Israel F Araujo, Daniel K Park, Teresa B Ludermir, Wilson R Oliveira, Francesco Petruccione, and Adenilton J Da Silva. Configurable sublinear circuits for quantum state preparation. Quantum Information Processing, 22(2): 123, 2023. Summary of the Invention

[0015] The present application provides a method for constructing an excitation operator in a variational quantum eigensolution algorithm, so as to reduce the number of CNOT gates used and reduce the depth of quantum circuits.

[0016] The present application provides a method for constructing an excitation operator in a variational quantum eigensolution algorithm, comprising the following steps:

[0017] By performing basis transformation on the CRY gate, a quantum circuit of a single excitation operator is constructed.

[0018] In the above technical solution, by performing basis transformation on the CRY gates, a quantum circuit of a single excitation operator is constructed, thereby reducing the number of CNOT gates used and the depth of the quantum circuit.

[0019] In a specific embodiment, it also includes:

[0020] By performing basis transformation on the C3RY gate, a quantum circuit of a double excitation operator is constructed.

[0021] In the above technical solution, by performing basis transformation on CRY gates, a quantum circuit of a single excitation operator is constructed; by performing basis transformation on C3RY gates, a quantum circuit of a double excitation operator is constructed, thereby reducing the number of CNOT gates used and the depth of the quantum circuit.

[0022] In a specific embodiment, the CRY gate comprises a CRY(2θ) gate;

[0023] The single excitation operator The matrix is:

[0024]

[0025] The matrix of the CRY(2θ) gate is:

[0026]

[0027] By performing basis transformation on the CRY gate, the steps to construct the quantum circuit of the single excitation operator are:

[0028] Interchange the basis |01> and the basis |11> of the CRY(2θ) gate to obtain the matrix (3):

[0029]

[0030] The construction of the quantum circuit of the single excitation operator is completed.

[0031] In a specific embodiment, the C3RY gate comprises a C3RY(2θ) gate;

[0032] The double excitation operator The matrix is:

[0033]

[0034] The matrix of the C3RY(2θ) gate is:

[0035]

[0036] By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are:

[0037] The basis |1110> of the C3RY gate is interchanged with the basis |1100>, and the basis |1111> is interchanged with the basis |0011> to obtain the matrix (4), thus completing the construction of the quantum circuit of the double excitation operator.

[0038] In a specific embodiment, the C3RY gate comprises a C3RY(2θ) gate;

[0039] The double excitation operator The matrix is:

[0040]

[0041] The matrix of the C3RY(2θ) gate is:

[0042]

[0043] By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are:

[0044] The basis |1110> of the C3RY gate is swapped with the basis |0011>, and the basis |1111> is swapped with the basis |1100>, and the matrix (6) is obtained:

[0045]

[0046] Complete the construction of the quantum circuit of the double excitation operator.

[0047] In a specific embodiment, it also includes:

[0048] The quantum circuit of the single excitation operator and the double excitation operator are directly constructed as quantum circuits by a basis transformation method.

[0049] In a specific embodiment,

[0050] The quantum circuit of the single excitation operator includes three CNOT gates and two RY gates.

[0051] In a specific embodiment,

[0052] The quantum circuit of the double excitation operator includes twenty-six CNOT gates, fourteen RY gates and four X gates.

[0053] In a specific implementation scheme, the basis |01> and the basis |11> of the CRY(2θ) gate are interchanged through a CNOT gate with quantum bit q as the control bit and quantum bit p as the controlled bit.

[0054] In a specific implementation scheme, the CNOT gate with qubit s as the control bit and qubit p as the controlled bit is first applied; then the CNOT gate with qubit s as the control bit and qubit q as the controlled bit is applied, and finally the 0-CNOT gate with qubit s as the control bit and qubit r as the controlled bit is applied to interchange the basis |1110> of the C3RY gate with the basis |1100>, and the basis |1111> with the basis |0011>;

[0055] Alternatively, by first applying X gates to qubits r and s respectively, and then applying CNOT gates with qubit s as the control bit to qubits p, q and r respectively, the basis |1110> of the C3RY gate is interchanged with the basis 0011>, and the basis |1111> is interchanged with the basis |1100>. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 The single excitation operator provided in the embodiment of the present application The overall circuit structure diagram;

[0057] Figure 2 A quantum circuit diagram for decomposing a CRY gate into a CNOT gate and a RY gate provided in an embodiment of the present application;

[0058] Figure 3 A state diagram of a CNOT gate with three gates intersecting provided in an embodiment of the present application that can exchange two quantum bits;

[0059] Figure 4 The single excitation operator provided in the embodiment of the present application Specific circuit structure diagram;

[0060] Figure 5 The double excitation operator provided in the embodiment of the present application The overall circuit structure diagram obtained by the first construction method;

[0061] Figure 6 The double excitation operator provided in the embodiment of the present application The overall circuit structure diagram obtained by the second construction method;

[0062] Figure 7A schematic diagram of a structure in which a C3RY gate provided in an embodiment of the present application is decomposed into a CNOT gate and a CRY gate by a V4 decomposition method;

[0063] Figure 8 The single excitation operator provided in the embodiment of the present application The specific implementation quantum circuit diagram;

[0064] Fig. 9 The double excitation operator is realized based on the method 1 provided in the embodiment of the present application. The overall quantum circuit diagram of

[0065] Fig.10 The double excitation operator is realized based on the second method provided in the embodiment of the present application. The overall quantum circuit diagram of

[0066] Fig.11 A diagram showing the decomposition results of the C3RY(2.4) gate provided in an embodiment of the present application based on the V4 decomposition method;

[0067] Fig.12 A flowchart of a method for constructing an excitation operator in a variational quantum eigensolution algorithm provided in an embodiment of the present application. DETAILED DESCRIPTION

[0068] The present application is further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present application will become clearer and more specific.

[0069] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0070] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0071] To facilitate understanding of the construction method of the excitation operator in the variational quantum eigensolution algorithm provided in the embodiment of the present application, its application scenario is first explained. The construction method of the excitation operator in the variational quantum eigensolution algorithm provided in the embodiment of the present application is used to reduce the number of CNOT gates used and reduce the depth of the quantum circuit. The implementation of the VQE algorithm requires the transformation of the fermion excitation operator to construct a quantum circuit. Existing transformation methods, such as Jordan-Wigner, Parity basis, Bravyi-Kitaev and Qubit-Excitation, all convert the first excitation operator into a Pauli string, and then convert the Pauli string into a quantum circuit. Although this goal can be achieved, the number of CNOT gates used is large, resulting in an excessive depth of the quantum circuit. For current NISQ devices, affected by various noises and operating errors, the shallower the depth of the quantum circuit (the fewer the number of CNOT gates used), the easier it is to obtain high-quality calculation results. Therefore, designing a better excitation operator transformation method is a very important research direction. To this end, the present application provides a method for constructing an excitation operator in a variational quantum eigensolution algorithm to reduce the number of CNOT gates used and the depth of quantum circuits. The method is described in detail below with reference to specific drawings.

[0072] refer to Figures 1 to 12 , Figure 1 The single excitation operator provided in the embodiment of the present application The overall circuit structure diagram; Figure 2 A quantum circuit diagram for decomposing a CRY gate into a CNOT gate and a RY gate provided in an embodiment of the present application; Figure 3 A state diagram of a CNOT gate with three gates intersecting provided in an embodiment of the present application that can exchange two quantum bits; Figure 4 The single excitation operator provided in the embodiment of the present application Specific circuit structure diagram; Figure 5 The double excitation operator provided in the embodiment of the present application The overall circuit structure diagram obtained by the first construction method; Figure 6 The double excitation operator provided in the embodiment of the present application The overall circuit structure diagram obtained by the second construction method; Figure 7 A schematic diagram of a structure in which a C3RY gate provided in an embodiment of the present application is decomposed into a CNOT gate and a CRY gate by a V4 decomposition method; Figure 8 The single excitation operator provided in the embodiment of the present application The specific implementation quantum circuit diagram; Fig. 9 The double excitation operator is realized based on the method 1 provided in the embodiment of the present application. The overall quantum circuit diagram of Fig.10 The double excitation operator is realized based on the second method provided in the embodiment of the present application. The overall quantum circuit diagram of Fig.11 A diagram showing the decomposition results of the C3RY(2.4) gate provided in an embodiment of the present application based on the V4 decomposition method; Fig.12 A flowchart of a method for constructing an excitation operator in a variational quantum eigensolution algorithm provided in an embodiment of the present application.

[0073] exist Fig.12 In the embodiment of the present application, a method for constructing an excitation operator in a variational quantum eigensolution algorithm is provided, comprising the following steps:

[0074] By performing basis transformation on the CRY gate, a quantum circuit of a single excitation operator is constructed.

[0075] In the above technical solution, by performing basis transformation on the CRY gates, a quantum circuit of a single excitation operator is constructed, thereby reducing the number of CNOT gates used and the depth of the quantum circuit.

[0076] In a specific embodiment, it also includes:

[0077] By performing basis transformation on the C3RY gate, a quantum circuit of a double excitation operator is constructed.

[0078] In the above technical solution, by performing basis transformation on CRY gates, a quantum circuit of a single excitation operator is constructed; by performing basis transformation on C3RY gates, a quantum circuit of a double excitation operator is constructed, thereby reducing the number of CNOT gates used and the depth of the quantum circuit.

[0079] In a specific embodiment, the CRY gate comprises a CRY(2θ) gate;

[0080] The single excitation operator The matrix is:

[0081]

[0082] The matrix of the CRY(2θ) gate is:

[0083]

[0084] By performing basis transformation on the CRY gate, the steps to construct the quantum circuit of the single excitation operator are:

[0085] Interchange the basis |01> and the basis |11> of the CRY(2θ) gate to obtain the matrix (3):

[0086]

[0087] The construction of the quantum circuit of the single excitation operator is completed.

[0088] It should be noted that by reversing each basis of formula (3), that is, exchanging the basis |00> with the basis |11>, and exchanging the basis |01> with the basis |10> (by applying an X gate to both quantum bits p and q), the same matrix as the single excitation operator can be obtained: formula (1). However, considering that the essential function of the single excitation operator is to realize the redistribution of the population between |01> and |10>, and formula (3) can already achieve this, the step of reversing each basis bit by bit can be omitted in practical applications to reduce the use of quantum gates.

[0089] refer to Figure 1 The overall structure of the quantum circuit that realizes the single excitation operator by performing a basis change method (basis transformation) on the CRY(2θ) gate is as follows Figure 1 Further, refer to Figure 2 and Figure 3 , since the CRY gate can be Figure 2 The method is decomposed into CNOT gate and RY gate, and combined with Figure 3 The three crossed CNOT gates shown can complete the exchange operation of the two quantum bit states. Figure 1 The structure shown can be further decomposed into Figure 4 The circuit structure shown in Figure 1 is as follows. Figure 4 As shown, this construction method can realize the function of the single-excitation operator using only three CNOT gates and two RY gates.

[0090] In a specific embodiment, the C3RY gate comprises a C3RY(2θ) gate;

[0091] The double excitation operator The matrix is:

[0092]

[0093] The matrix of the C3RY(2θ) gate is:

[0094]

[0095] By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are:

[0096] The basis |1110> of the C3RY gate is interchanged with the basis |1100>, and the basis |1111> is interchanged with the basis |0011> to obtain the matrix (4), thus completing the construction of the quantum circuit of the double excitation operator.

[0097] In a specific embodiment, the C3RY gate comprises a C3RY(2θ) gate;

[0098] The double excitation operator The matrix is:

[0099]

[0100] The matrix of the C3RY(2θ) gate is:

[0101]

[0102] By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are:

[0103] The basis |1110> of the C3RY gate is swapped with the basis |0011>, and the basis |1111> is swapped with the basis |1100>, and the matrix (6) is obtained:

[0104]

[0105] Complete the construction of the quantum circuit of the double excitation operator.

[0106] In a specific embodiment, it also includes:

[0107] The quantum circuit of the single excitation operator and the double excitation operator are directly constructed as quantum circuits by a basis transformation method.

[0108] In a specific embodiment,

[0109] The quantum circuit of the single excitation operator includes three CNOT gates and two RY gates.

[0110] In a specific embodiment,

[0111] The quantum circuit of the double excitation operator includes twenty-six CNOT gates, fourteen RY gates and four X gates.

[0112] In a specific implementation scheme, the basis |01> and the basis |11> of the CRY(2θ) gate are interchanged through a CNOT gate with quantum bit q as the control bit and quantum bit p as the controlled bit.

[0113] In a specific implementation scheme, the CNOT gate with qubit s as the control bit and qubit p as the controlled bit is first applied; then the CNOT gate with qubit s as the control bit and qubit q as the controlled bit is applied, and finally the 0-CNOT gate with qubit s as the control bit and qubit r as the controlled bit is applied to interchange the basis |1110> of the C3RY gate with the basis |1100>, and the basis |1111> with the basis |0011>;

[0114] Alternatively, by first applying X gates to qubits r and s respectively, and then applying CNOT gates with qubit s as the control bit to qubits p, q and r respectively, the basis |1110> of the C3RY gate is interchanged with the basis 0011>, and the basis |1111> is interchanged with the basis |1100>.

[0115] It should be noted that for the double excitation operator There are two construction methods:

[0116] Method 1: Interchange the basis |1110> of the C3RY gate with the basis |1100>, and the basis |1111> with the basis |0011> (this can be achieved by first applying a CNOT gate with qubit s as the control bit and qubit p as the controlled bit; then applying a CNOT gate with qubit s as the control bit and qubit q as the controlled bit, and finally applying a 0-CNOT gate with qubit s as the control bit and qubit r as the controlled bit), and obtain the matrix (4), completing the construction of the quantum circuit of the dual excitation operator. Considering that the 0-CNOT gate can be realized by 1 CNOT gate and 2 X gates, in this embodiment, for the dual excitation operator The overall structure of the quantum circuit obtained by the first construction method is as follows Figure 5 shown.

[0117] Method 2: Interchange the basis |1110> of the C3RY gate with the basis |0011>, and the basis |1111> with the basis |1100> (this can be achieved by first applying X gates to quantum bits r and s respectively, and then applying CNOT gates with quantum bit s as the control bit to quantum bits p, q and r respectively), and obtain the matrix (6); if it is to be consistent with the matrix expression of the double excitation operator: formula (4), just invert each basis bit by bit (this can be achieved by applying an X gate to each quantum bit). However, considering that the essential effect of the double excitation operator is to realize the redistribution of the population between |0011> and |1100>, and formula (6) can already achieve this, this step can be omitted in practical applications to reduce the use of quantum gates. Therefore, for the double excitation operator in this patent, The overall structure of the quantum circuit obtained by the second construction method is as follows Figure 6 shown.

[0118] The C3RY gate used in the above two methods can be Figure 7 V4 decomposition shown [5] Decomposed into CNOT and CRY gates. Combined with Figure 2 From the decomposition method of the CRY gate shown, it can be seen that no matter method 1 or method 2, for the double excitation operator, 26 CNOT gates, 14 RY gates and 4 X gates are used to implement it.

[0119] In the above technical solution, the present application proposes a low-cost construction method for the excitation operator used in the VQE algorithm by performing a basis transformation on the CRY gate and the C3RY gate:

[0120] For single-excitation operators, the method of the present application only needs to use three CNOT gates and two RY gates to achieve the target function;

[0121] For the double excitation operator, this application proposes two solutions, and both solutions only use 26 CNOT gates, 14 RY gates and 4 X gates to achieve the target function.

[0122] For single excitation operators and double excitation operators, compared with the current best Qubit-Excitation [4] Compared with the conventional schemes (using 4 and 48 CNOT gates respectively), the present application reduces 1 and 22 CNOT gates respectively, which reduces the overall implementation cost by about 45%. In the current NISQ (Noisy Intermediate-Scale Quantum) device era, it can significantly improve the experimental effect of the VQE (Variational Quantum Eigensolver) algorithm.

[0123] To further explain the method proposed by the present application for realizing the excitation operator at low cost, a single excitation operator and the double excitation operator As a specific embodiment, a specific quantum circuit is shown:

[0124] For the single excitation operator Based on the specific implementation of quantum circuits in this application, Figure 8 shown.

[0125] For the double excitation operator The specific overall quantum circuits based on Method 1 and Method 2 in this patent are as follows: Fig. 9 and Fig.10 shown.

[0126] Fig. 9 and Fig.10 The decomposition result of the C3RY(2.4) gate in the V4 decomposition method is as follows Fig.11 shown.

[0127] In the above technical solution, by performing basis transformation on CRY gates, a quantum circuit of a single excitation operator is constructed; by performing basis transformation on C3RY gates, a quantum circuit of a double excitation operator is constructed, thereby reducing the number of CNOT gates used and the depth of the quantum circuit.

[0128] Those skilled in the art will appreciate that the present application may be implemented as a system, method or computer program product.

[0129] Therefore, the present disclosure may be specifically implemented in the following forms, namely: it may be completely hardware, it may be completely software (including firmware, resident software, microcode, etc.), or it may be a combination of hardware and software, generally referred to herein as a "circuit", "module" or "system". In addition, in some embodiments, the present application may also be implemented in the form of a computer program product in one or more computer-readable media, and the computer-readable medium may contain computer-readable program code.

[0130] Any combination of one or more computer-readable media can be used. Computer-readable media can be computer-readable signal media or computer-readable storage media. Computer-readable storage media can be, for example, but not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices or devices, or any combination of the above. More specific examples (non-exhaustive list) of computer-readable storage media include: electrical connections with one or more wires, portable computer disks, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROM or flash memory), optical fibers, portable compact disk read-only memories (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the above. In this document, computer-readable storage media can be any tangible medium containing or storing a program, which can be used by an instruction execution system, device or device or used in combination with it.

[0131] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art can change, modify, replace and modify the above embodiments within the scope of the present application. On this basis, a variety of replacements and improvements can be made to the present application, all of which fall within the scope of protection of the present application.

Claims

1. A method for constructing an excitation operator in a variational quantum eigensolver algorithm, characterized in that: The following steps are involved: By performing basis transformation on the CRY gate, a quantum circuit of a single excitation operator is constructed.

2. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 1, characterized in that: Also includes: By performing basis transformation on the C3RY gate, a quantum circuit of a double excitation operator is constructed.

3. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 2, characterized in that: The CRY gate comprises a CRY (2θ) gate; The single excitation operator The matrix is: The matrix of the CRY(2θ) gate is: By performing basis transformation on the CRY gate, the steps to construct the quantum circuit of the single excitation operator are: Interchange the basis |01> and the basis |11> of the CRY(2θ) gate to obtain the matrix (3): The construction of the quantum circuit of the single excitation operator is completed.

4. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 3, characterized in that: The C3RY gate includes a C3RY(2θ) gate; The double excitation operator The matrix is: The matrix of the C3RY(2θ) gate is: By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are: The basis |1110> of the C3RY gate is interchanged with the basis |1100>, and the basis |1111> is interchanged with the basis |0011> to obtain the matrix (4), thus completing the construction of the quantum circuit of the double excitation operator.

5. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 3, characterized in that: The C3RY gate includes a C3RY(2θ) gate; The double excitation operator The matrix is: The matrix of the C3RY(2θ) gate is: By performing a basis transformation on the C3RY gate, the steps to construct the quantum circuit of the double excitation operator are: The basis |1110> of the C3RY gate is swapped with the basis |0011>, and the basis |1111> is swapped with the basis |1100>, and the matrix (6) is obtained: Complete the construction of the quantum circuit of the double excitation operator.

6. The method for constructing an excitation operator in a variational quantum eigensolution algorithm according to claim 4 or 5, characterized in that: Also includes: The quantum circuit of the single excitation operator and the double excitation operator are directly constructed as quantum circuits by a basis transformation method.

7. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 6, characterized in that: The quantum circuit of the single excitation operator includes three CNOT gates and two RY gates.

8. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 7, characterized in that: The quantum circuit of the double excitation operator includes twenty-six CNOT gates, fourteen RY gates and four X gates.

9. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 8, characterized in that: The basis |01> and the basis |11> of the CRY(2θ) gate are interchanged through a CNOT gate with quantum bit q as the control bit and quantum bit p as the controlled bit.

10. The method for constructing an excitation operator in a variational quantum eigensolver algorithm according to claim 9, characterized in that: By first applying a CNOT gate with qubit s as the control bit and qubit p as the controlled bit; then applying a CNOT gate with qubit s as the control bit and qubit q as the controlled bit, and finally applying a 0-CNOT gate with qubit s as the control bit and qubit r as the controlled bit, the basis |1110> of the C3RY gate is exchanged with the basis |1100>, and the basis |1111> with the basis |0011>; Alternatively, by first applying X gates to qubits r and s respectively, and then applying CNOT gates with qubit s as the control bit to qubits p, q and r respectively, the basis |1110> of the C3RY gate is interchanged with the basis 0011>, and the basis |1111> is interchanged with the basis |1100>.

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