Expected value calculation system, expected value calculation device, and expected value calculation method

Abstract

To improve the calculation accuracy of expected value calculation using a quantum computer.SOLUTION: A quantum computer calculates an expected value of a calculation object by using a quantum circuit. An update part acquires the expected value from the quantum computer, acquires an updated parameter by updating a parameter the quantum circuit on the basis of the expected value, and performs update processing for controlling the quantum computer so as to calculate the expected value by using the quantum circuit with the updated parameter applied thereto. The update part acquires a specific parameter by performing update processing the prescribed number of times. A calculation part calculates an expected value with accuracy higher than the quantum computer does by using the quantum circuit that applies the specific parameter.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an expected value calculation technique using a quantum computer. [Background technology]

[0002] A quantum computer is a computer that uses the phenomena of quantum mechanics to perform calculations. A quantum computer may calculate the expected value of an object using a quantum circuit, which is a quantum computing model that describes a quantum algorithm.

[0003] Regarding quantum computers, a method for removing noise from quantum devices is known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-126618 A Summary of the Invention [Problem to be solved by the invention]

[0005] One example of a quantum computer is the Noisy Intermediate-Scale Quantum (NISQ) device, which is a medium-scale quantum computer that uses tens to hundreds of quantum bits.

[0006] In NISQ devices, quantum error correction is insufficient or not performed at all, so the calculation result of the expected value fluctuates due to the influence of noise. The influence of noise depends on the size of the quantum circuit, which is a quantum computing model that describes the quantum algorithm. The size of the quantum circuit is expressed by, for example, the number of quantum bits and the number of gates.

[0007] This problem is not limited to expectation value calculations using NISQ devices, but occurs in expectation value calculations using various quantum computers that are affected by noise.

[0008] In one aspect, the present invention aims to improve the calculation accuracy of expected value calculations using a quantum computer. [Means for solving the problem]

[0009] In one proposal, the expectation calculation system includes a quantum computer, an update unit, and a calculation unit. The quantum computer calculates the expectation value of the calculation target using a quantum circuit.

[0010] The update unit performs an update process that acquires an expected value from the quantum computer, updates parameters of the quantum circuit based on the expected value to obtain updated parameters, and controls the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied. The update unit performs the update process a predetermined number of times to obtain a specific parameter.

[0011] The calculation unit uses a quantum circuit to which specific parameters are applied to calculate the expected value with greater accuracy than a quantum computer. Effect of the Invention

[0012] According to one aspect, it is possible to improve the calculation accuracy of expected value calculations using a quantum computer. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 illustrates a first VQA. [Diagram 2] FIG. 13 is a diagram illustrating a second VQA. [Diagram 3] FIG. 2 is a functional configuration diagram of an expected value calculation system according to an embodiment. [Figure 4] FIG. 1 is a configuration diagram of a first quantum computer system according to an embodiment. [Diagram 5] FIG. 1 illustrates a quantum circuit. [Figure 6] FIG. 1 is a hardware configuration diagram of a quantum computer. [Figure 7] FIG. 1 is a first functional configuration diagram of a server. [Figure 8] FIG. 13 is a diagram showing changes in parameters. [Figure 9] FIG. 13 is a diagram showing expected values ​​calculated using parameters. [Figure 10] FIG. 13 is a diagram showing the calculation results of the ground state energy of a molecule. [Figure 11] 13 is a flowchart of an expected value calculation process. [Figure 12] FIG. 11 is a configuration diagram of a second quantum computer system according to an embodiment. [Figure 13] FIG. 2 is a second functional configuration diagram of the server. [Figure 14] FIG. 2 is a hardware configuration diagram of an information processing device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0015] The Variational Quantum Algorithm (VQA) is known as a variational algorithm for NISQ devices. VQA is an algorithm that alternates between quantum computers and classical computers. VQA is used in various fields such as quantum chemical calculations and combinatorial optimization problems.

[0016] 1 shows an example of the first VQA. A quantum computer 101 calculates an expected value of a calculation target by executing a calculation of a quantum circuit. For example, in the case of quantum chemical calculation, physical quantities such as the ground state energy of a molecule and the position of an electron are used as the calculation target.

[0017] The classical computer 102 acquires the expected value output from the quantum computer 101, and updates the parameters of the quantum circuit based on the acquired expected value. Then, the classical computer 102 outputs the updated parameters to the quantum computer 101. The quantum computer 101 sets the updated parameters in the quantum circuit, and executes the calculation of the quantum circuit again.

[0018] By repeating this update process until the expectation value converges, a quantum circuit with appropriate parameters can be generated. Since the quantum computer 101 and the classical computer 102 are used alternately in VQA, expectation value calculations can be performed even if the quantum computer 101 is a NISQ device using a relatively small quantum circuit.

[0019] However, when the quantum computer 101 is a NISQ device, the accuracy of the expected value output from the quantum computer 101 decreases due to the influence of noise. In this case, it is difficult to determine whether the expected value has converged based on the expected value with low accuracy, making it difficult to optimize the parameters by the classical computer 102. The larger the scale of the quantum circuit, the greater the degree to which the accuracy of the expected value decreases.

[0020] Therefore, in order to prevent the accuracy of the expected value from decreasing, it is possible to use a quantum simulator instead of the quantum computer 101. The quantum simulator is a program that simulates the calculation of quantum bits by the quantum computer 101 on a classical computer, and can perform calculation of quantum bits without noise. The quantum simulator is sometimes called a quantum computer simulator.

[0021] Fig. 2 shows an example of a second VQA. In the VQA in Fig. 2, a quantum simulator 201 is used instead of the quantum computer 101 in Fig. 1. The quantum simulator 201 calculates the expected value of the calculation target by executing a calculation of a quantum circuit.

[0022] The classical computer 102 acquires the expected value output from the quantum simulator 201, and updates the parameters of the quantum circuit based on the acquired expected value. Then, the classical computer 102 inputs the updated parameters to the quantum simulator 201. The quantum simulator 201 sets the updated parameters in the quantum circuit, and executes the calculation of the quantum circuit again.

[0023] By using the quantum simulator 201, it is possible to perform noise-free expected value calculations, improving the accuracy of the expected value. This makes it easier to optimize parameters using the classical computer 102.

[0024] However, since the expected value calculation by the quantum simulator 201 imposes a heavy load, the calculation time increases exponentially with an increase in the number of quantum bits. For this reason, the expected value calculation, which takes a long time, is repeated until the expected value converges.

[0025] Fig. 3 shows an example of the functional configuration of an expected value calculation system according to an embodiment. The expected value calculation system 301 in Fig. 3 includes a quantum computer 311, an update unit 312, and a calculation unit 313. The quantum computer 311 calculates the expected value of a calculation target using a quantum circuit.

[0026] The update unit 312 performs an update process to obtain an expected value from the quantum computer 311, update the parameters of the quantum circuit based on the expected value to obtain updated parameters, and control the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied. The update unit 312 performs the update process a predetermined number of times to obtain a specific parameter.

[0027] The calculation unit 313 calculates the expected value with higher accuracy than the quantum computer 311, using a quantum circuit to which specific parameters are applied.

[0028] According to the expected value calculation system of FIG. 3, it is possible to improve the calculation accuracy of the expected value calculation using a quantum computer.

[0029] Fig. 4 shows a configuration example of a first quantum computer system according to an embodiment. The quantum computer system in Fig. 4 corresponds to the expected value calculation system 301 in Fig. 3, and calculates the expected value of a calculation target using a VQA. As the VQA, a variational quantum eigensolver (VQE), a quantum approximate optimization algorithm (QAOA), a quantum neural network (QNN), or the like is used.

[0030] The quantum computer system of Fig. 4 includes a quantum computer 401 and a server 402. The quantum computer 401 and the server 402 are hardware. The quantum computer 401 corresponds to the quantum computer 311 of Fig. 3 and is, for example, a NISQ device. The server 402 is a classical computer.

[0031] The server 402 communicates with the quantum computer 401 via a communication line 403. First, the server 402 transmits to the quantum computer 401 the initial values ​​of each of a plurality of quantum bits and information on a quantum circuit according to the target of calculation.

[0032] The quantum computer 401 performs a quantum bit operation indicated by the quantum circuit information on the initial value of each quantum bit to obtain a value of each quantum bit indicating an expected value of the calculation target. Then, the quantum computer 401 transmits the obtained value of each quantum bit to the server 402.

[0033] The server 402 updates the parameters of the quantum circuit based on the expected values ​​indicated by the received values ​​of each quantum bit, and transmits information about the quantum circuit including the updated parameters to the quantum computer 401.

[0034] The quantum computer 401 performs a quantum bit operation on the initial value of each quantum bit, which is indicated by the information of the quantum circuit including the updated parameters, to obtain the value of each quantum bit indicating the expected value of the calculation target. As a result, the expected value of the calculation target is updated.

[0035] The server 402 determines the parameter values ​​of the quantum circuit by repeating such an update process multiple times. Then, the server 402 calculates the expected value of the computation target by a quantum simulator using the quantum circuit to which the determined parameter values ​​are applied.

[0036] Fig. 5 shows an example of a quantum circuit. The quantum circuit in Fig. 5 includes an ansatz 501, an operator circuit 502, and a measurement circuit 503. The ansatz 501 includes an initialization circuit 511 and a generation circuit 512, and generates a quantum state using parameters of the quantum circuit. The ansatz 501 is an example of a first circuit, and the operator circuit 502 is an example of a second circuit.

[0037] The initialization circuit 511 sets an initial value for each quantum bit. In the example of FIG. 5, the initial value for each quantum bit is a logical value "0". The generation circuit 512 includes a plurality of quantum gates, and generates a trial state from the initial values ​​of each of the plurality of quantum bits. The trial state represents a quantum state that is a trial function of the VQA. Each quantum gate of the generation circuit 512 performs a quantum bit operation according to a rotation angle θ. The rotation angle θ has a different value for each quantum gate. The rotation angle θ is an example of a parameter of a quantum circuit.

[0038] The operator circuit 502 includes a plurality of quantum gates representing the operator to be calculated, and calculates the expected value of the operator from the trial state generated by the Ansatz 501. The measurement circuit 503 measures the expected value calculated by the operator circuit 502, and outputs the value of each quantum bit indicating the measured expected value. The value of each quantum bit that is output is a logical value of "0" or a logical value of "1".

[0039] For example, in quantum chemical calculations, when the calculation target is the ground state of a molecule, the trial state corresponds to the electronic state of the molecule, and the operator of the calculation target corresponds to the Hamiltonian of the molecular energy. In addition, in combinatorial optimization problems, when the calculation target is the maximum or minimum value of an objective function, the trial state corresponds to a candidate solution, and the operator of the calculation target corresponds to the objective function.

[0040] Figure 6 shows an example of the hardware configuration of the quantum computer 401 in Figure 4. The quantum computer 401 in Figure 6 includes a communication interface 611, a control device 612, and a quantum system 613. These components are hardware.

[0041] The communication interface 611 is a communication circuit that is connected to the communication line 403 and performs data conversion associated with communication. The quantum system 613 includes a quantum device that realizes a plurality of quantum bits.

[0042] The communication interface 611 receives the initial values ​​of each of the multiple quantum bits and the information of the quantum circuit from the server 402, and outputs them to the control device 612. The control device 612 generates a control signal using the initial values ​​of each quantum bit and the information of the quantum circuit, and outputs it to the quantum system 613.

[0043] The quantum system 613 performs quantum bit manipulation according to the control signal to obtain a value of each quantum bit indicating an expected value of the calculation target from the initial value of each quantum bit. Then, the control device 612 transmits the value of each quantum bit obtained by the quantum system 613 to the server 402 via the communication interface 611.

[0044] Thereafter, the communication interface 611 receives quantum circuit information including the updated parameters from the server 402, and outputs it to the control device 612. The quantum circuit information including the updated parameters is, for example, information of the generation circuit 512 in which the updated rotation angle θ is set. The control device 612 generates a control signal using the initial values ​​of each quantum bit and the quantum circuit information, and outputs it to the quantum system 613.

[0045] The quantum system 613 performs quantum bit operations in accordance with the control signal to obtain values ​​of each quantum bit that indicate updated expected values ​​from the initial values ​​of each quantum bit. Then, the control device 612 transmits the values ​​of each quantum bit obtained by the quantum system 613 to the server 402 via the communication interface 611.

[0046] Fig. 7 shows a first example of a functional configuration of server 402 in Fig. 4. Server 402 in Fig. 7 includes a communication unit 711, an update unit 712, a calculation unit 713, an output unit 714, and a storage unit 715. The update unit 712 and the calculation unit 713 correspond to the update unit 312 and the calculation unit 313 in Fig. 3, respectively.

[0047] The communication unit 711 communicates with the quantum computer 401 via the communication line 403. The storage unit 715 stores parameters 721 of the quantum circuit.

[0048] First, the updating unit 712 transmits the initial values ​​of each of the multiple quantum bits and information on the quantum circuit including the initial values ​​of the parameters 721 to the quantum computer 401 via the communication unit 711. Then, the updating unit 712 receives the value of each quantum bit indicating the expected value of the calculation target from the quantum computer 401 via the communication unit 711, thereby acquiring the expected value from the quantum computer 401.

[0049] Next, the updating unit 712 updates the parameters 721 based on the expected value indicated by the value of each quantum bit so that the expected value approaches an optimal value. The updating unit 712 may update the parameters 721 using a gradient method such as the steepest descent method. The optimal expected value may be, for example, the minimum value of the molecule's energy, or the maximum or minimum value of the objective function.

[0050] Next, the updating unit 712 transmits information about the quantum circuit, including the updated parameters 721, to the quantum computer 401, thereby controlling the quantum computer 401 to calculate the expected value using the quantum circuit to which the updated parameters 721 have been applied. Then, the updating unit 712 receives from the quantum computer 401 the value of each quantum bit indicating the updated expected value.

[0051] The update unit 712 repeats such an update process multiple times to determine the final value of the parameter 721. The update unit 712 may determine the value of the parameter 721 when the expected value converges as the final value, or may determine the value of the parameter 721 obtained by repeating the update process a specified number of times as the final value.

[0052] By repeating the update process until the expected value converges, the final value of the parameter 721 becomes closer to the optimum value than if the update process was terminated before the expected value converges. The final value of the parameter 721 is an example of a particular parameter.

[0053] Next, the calculation unit 713 calculates the expected value of the calculation target by the quantum simulator using the quantum circuit to which the final value of the parameter 721 is applied. The quantum simulator is not affected by noise in the quantum computer 401, and therefore can calculate the expected value with higher accuracy than the quantum computer 401. The expected value calculation using the quantum simulator is executed only once.

[0054] The output unit 714 outputs the expected value calculated by the calculation unit 713. In the case of a combinatorial optimization problem, the output unit 714 outputs the maximum or minimum value of the objective function as the expected value, and also outputs a solution corresponding to the expected value.

[0055] Fig. 8 shows an example of the change in parameter 721 in Fig. 7. In this example, the quantum computer 401 is a NISQ device. The horizontal axis represents the number of iterations of the update process, and the vertical axis represents the value of parameter 721. A dashed line 801 represents the optimal value of parameter 721 corresponding to the optimal value of the expected value, and a curve 802 represents the change in parameter 721 with the iterations of the update process.

[0056] In this example, the final value 803 of the parameter 721 obtained by repeating the update process multiple times approaches the optimum value indicated by the dashed line 801, and the error between the final value 803 and the optimum value is small. Thus, even if it is difficult to determine whether the expected value has converged, repeating the update process multiple times often causes the final value 803 of the parameter 721 to approach the optimum value.

[0057] Fig. 9 shows an example of an expectation value calculated using the parameter 721. Fig. 9(a) shows an example of an expectation value that changes with a change in the parameter 721 shown in Fig. 8. The horizontal axis represents the number of iterations of the update process, and the vertical axis represents the expectation value. A dashed line 901 represents the optimal value of the expectation value, and a curve 902 represents the change in the expectation value calculated by the quantum computer 401 according to the iterations of the update process.

[0058] In this example, the effect of noise in the quantum computer 401 increases the error between the expected value 903 obtained by repeating the update process multiple times and the optimal value indicated by the dashed line 901. Thus, when the quantum computer 401 is a NISQ device, even if the final value 803 of the parameter 721 approaches the optimal value, the effect of noise reduces the accuracy of the expected value 903 calculated by the quantum computer 401 using the final value 803.

[0059] 9(b) shows an example of an expectation calculated by a quantum simulator using a quantum circuit to which the final value 803 of the parameter 721 is applied. The horizontal axis represents the number of iterations of the update process, and the vertical axis represents the expectation. The dashed line 901 represents the optimal value of the expectation, and the expectation 904 represents the expectation calculated by the quantum simulator after the iterations of the update process are completed.

[0060] Since the expected value 904 is not affected by noise in the quantum computer 401, the error between the expected value 904 and the optimum value indicated by the dashed line 901 is smaller than the error between the expected value 903 in Fig. 9(a) and the optimum value. In this way, even if the quantum computer 401 is a NISQ device, if the final value 803 of the parameter 721 is close to the optimum value, the accuracy of the expected value 904 calculated by the quantum simulator using the final value 803 will be high.

[0061] Note that even if the final value of parameter 721 is not very close to the optimal value, the accuracy of the expected value calculated by the quantum simulator is higher than the accuracy of the expected value calculated by the quantum computer 401 using the same final value. Therefore, according to the quantum computer system of Fig. 4, the accuracy of the calculated expected value is improved by performing the expected value calculation by the noise-free quantum simulator using the final value of parameter 721 obtained by VQA.

[0062] Figure 10 shows an example of the calculation result of the ground state energy of a molecule in quantum chemical calculation. The vertical axis represents the error (hartree) between the calculated expected value and the optimal value. H2 represents a hydrogen molecule with two hydrogen atoms bonded, LiH represents a lithium hydride molecule, and Hchain4 represents a molecule with four hydrogen atoms bonded.

[0063] In this example, the parameters 721 are updated using VQE. sto-3g is used as the basis function representing the electronic state, and UCCSD (Unitary Coupled-Cluster Singles and Doubles) is used as the Ansatz. In addition, SPSA (Simultaneous Perturbation Stochastic Approximation) is used as the optimization method.

[0064] Bars 1001, 1002, and 1003 represent the error of the expected value calculated by quantum computer 401 using the final values ​​of parameters 721. Bars 1011, 1012, and 1013 represent the error of the expected value calculated by the quantum simulator using the final values ​​of parameters 721.

[0065] The error represented by bar 1011 is smaller than the error represented by bar 1001, the error represented by bar 1012 is smaller than the error represented by bar 1002, and the error represented by bar 1013 is smaller than the error represented by bar 1003. Therefore, for each molecule, the accuracy of the expected value of the ground state energy is improved by performing the expectation value calculation using a quantum simulator.

[0066] Fig. 11 is a flowchart showing an example of an expected value calculation process performed by the quantum computer system of Fig. 4. First, the update unit 712 of the server 402 determines the initial value of each of the multiple quantum bits, and transmits the initial value of each quantum bit and information on the quantum circuit including the initial value of the parameter 721 to the quantum computer 401 (step 1101).

[0067] Next, the quantum computer 401 performs quantum bit manipulation using the information of the quantum circuit to obtain the value of each quantum bit indicating the expected value of the calculation target from the initial value of each quantum bit (step 1102). Then, the quantum computer 401 transmits the value of each quantum bit indicating the expected value to the server 402.

[0068] Next, the update unit 712 of the server 402 updates the parameters 721 based on the expected values ​​indicated by the values ​​of each quantum bit so that the expected values ​​approach the optimal values ​​(step 1103), and checks whether the termination condition is satisfied (step 1104).

[0069] The termination condition may be a condition indicating that the expected value has converged, or may be a condition indicating that the number of updates of the parameter 721 has reached a specified number. The update unit 712 determines that the expected value has converged, for example, when the difference between the expected value indicated by the value of each quantum bit and the expected value indicated by the value of each quantum bit received in the past is smaller than a predetermined value. The specified number is, for example, an integer equal to or greater than 1.

[0070] If the termination condition is not satisfied (step 1104, NO), the update unit 712 transmits information about the quantum circuit, including the updated parameters 721, to the quantum computer 401 (step 1108).

[0071] The quantum computer 401 performs quantum bit manipulation using information about the quantum circuit including the updated parameters 721 to obtain the value of each quantum bit that indicates the updated expected value from the initial value of each quantum bit (step 1102). Then, the quantum computer system repeats the processes from step 1103 onwards.

[0072] If the termination condition is met (step 1104, YES), the update unit 712 determines the updated parameter 721 as the final value (step 1105).

[0073] Next, the calculation unit 713 obtains the final value of the parameter 721 from the storage unit 715, and calculates the expected value of the calculation target by the quantum simulator using the quantum circuit to which the final value is applied (step 1106). Then, the output unit 714 outputs the expected value calculated by the calculation unit 713 (step 1107). The output unit 714 may also output the solution corresponding to the expected value.

[0074] Fig. 12 shows a configuration example of a second quantum computer system according to an embodiment. The quantum computer system of Fig. 12 corresponds to the expected value calculation system 301 of Fig. 3, and has a configuration in which a Fault Tolerant Quantum Computer (FTQC) 1201 is added to the quantum computer system of Fig. 4. The FTQC 1201 is a hardware quantum computer having an error correction function. The FTQC 1201 corresponds to the calculation unit 313 of Fig. 3.

[0075] The server 402 communicates with the FTQC 1201 via the communication line 1202. The server 402 determines the parameter values ​​of the quantum circuit by repeating an update process similar to that of the quantum computer system of Fig. 4 multiple times. Then, the server 402 transmits the initial values ​​of each quantum bit and information about the quantum circuit including the determined parameter values ​​to the FTQC 1201.

[0076] The FTQC 1201 performs a quantum bit operation indicated by the quantum circuit information on the initial value of each quantum bit to obtain the value of each quantum bit indicating the expected value of the calculation target. Then, the FTQC 1201 transmits the obtained quantum bit value to the server 402.

[0077] Unlike the quantum computer 401, the FTQC1201 has an error correction function, and therefore can calculate the expected value with higher accuracy than the quantum computer 401. The expected value calculation by the FTQC1201 is executed only once. The hardware configuration of the FTQC1201 is the same as the hardware configuration of the quantum computer 401 in FIG. 6.

[0078] For combinatorial optimization problems, the FTQC 1201 also transmits to the server 402 the value of each quantum bit that indicates the solution corresponding to the expected value.

[0079] Fig. 13 shows a second example of the functional configuration of the server 402 in Fig. 12. The server 402 in Fig. 13 has a configuration in which the calculation unit 713 is removed from the server 402 in Fig. 7. A communication unit 711 communicates with the FTQC 1201 via the communication line 1202.

[0080] The update unit 712 determines the final value of the parameter 721 by repeating an update process multiple times similar to that of the quantum computer system of Fig. 4. Then, the update unit 712 transmits the initial values ​​of each quantum bit and information on the quantum circuit including the final value of the parameter 721 to the FTQC1201 via the communication unit 711.

[0081] The update unit 712 receives the value of each quantum bit indicating the expected value of the calculation target from the FTQC 1201 via the communication unit 711, and acquires the expected value indicated by the value of each quantum bit. The output unit 714 outputs the acquired expected value.

[0082] In the case of a combinatorial optimization problem, the update unit 712 also receives from the FTQC 1201 the value of each quantum bit indicating a solution corresponding to the expected value, and acquires the solution indicated by the value of each quantum bit. The output unit 714 then outputs the acquired solution.

[0083] The configuration of the expected value calculation system 301 in FIG. 3 is merely an example, and some of the components may be omitted or changed depending on the application or conditions of the expected value calculation system.

[0084] The configurations of the quantum computer systems in Figures 4 and 12 are merely examples, and some of the components may be omitted or changed depending on the use or conditions of the quantum computer system. The configuration of the quantum computer 401 in Figure 6 is merely an example, and some of the components may be omitted or changed depending on the use or conditions of the quantum computer system. The configuration of the server 402 in Figures 7 and 13 is merely an example, and some of the components may be omitted or changed depending on the use or conditions of the quantum computer system.

[0085] The flowchart in FIG. 11 is merely an example, and some of the processing may be omitted or changed depending on the configuration or conditions of the quantum computer system.

[0086] The VQA shown in Figures 1 and 2 is merely an example, and the VQA may be implemented in another manner. The quantum circuit shown in Figure 5 is merely an example, and the quantum circuit changes depending on the calculation target. The parameters 721 shown in Figure 8 and the expected values ​​shown in Figure 9 are merely an example, and the calculated parameters 721 and expected values ​​change depending on the calculation target. The calculation result shown in Figure 10 is merely an example, and the calculation result of the basis energy changes depending on the molecule.

[0087] Fig. 14 shows an example of the hardware configuration of an information processing device (computer) used as the server 402 in Fig. 7 and Fig. 13. The information processing device in Fig. 14 includes a CPU (Central Processing Unit) 1401, a memory 1402, an input device 1403, an output device 1404, an auxiliary storage device 1405, a medium drive device 1406, and a network connection device 1407. These components are hardware and are connected to each other via a bus 1408.

[0088] The memory 1402 is, for example, a semiconductor memory such as a Read Only Memory (ROM) or a Random Access Memory (RAM), and stores programs and data used in processing. The memory 1402 may operate as the storage unit 715 in FIGS.

[0089] The CPU 1401 (processor) executes a program using the memory 1402, for example, to operate as the update unit 712 in FIGS. 7 and 13 and the calculation unit 713 in FIG.

[0090] The input device 1403 is, for example, a keyboard, a pointing device, etc., and is used to input instructions or information from a user or operator. The output device 1404 is, for example, a display device, a printer, etc., and is used to output inquiries or instructions to a user or operator, and processing results. The processing results may be an expected value of a calculation target. The output device 1404 may operate as the output unit 714 in FIG. 7 and FIG. 13.

[0091] The auxiliary storage device 1405 is, for example, a magnetic disk device, an optical disk device, a magneto-optical disk device, a tape device, or the like. The auxiliary storage device 1405 may be a hard disk drive or a solid state drive (SSD). The information processing device can store programs and data in the auxiliary storage device 1405 and use them by loading them into the memory 1402. The auxiliary storage device 1405 may operate as the storage unit 715 in FIG. 7 and FIG. 13.

[0092] The medium drive device 1406 drives the portable recording medium 1409 and accesses the recorded contents. The portable recording medium 1409 is a memory device, a flexible disk, an optical disk, a magneto-optical disk, etc. The portable recording medium 1409 may be a CD-ROM (Compact Disk Read Only Memory), a DVD (Digital Versatile Disk), a USB (Universal Serial Bus) memory, etc. A user or operator can store programs and data in the portable recording medium 1409 and load them into the memory 1402 for use.

[0093] Thus, the computer-readable recording medium that stores the program and data used in the processing is a physical (non-transitory) recording medium such as the memory 1402, the auxiliary storage device 1405, or the portable recording medium 1409.

[0094] The network connection device 1407 is a communication circuit that is connected to the communication line 403 and the communication line 1202 and performs data conversion associated with communication. The network connection device 1407 may operate as the output unit 714 in Fig. 7 and Fig. 13. The information processing device can receive programs and data from an external device via the network connection device 1407 and load them into the memory 1402 for use.

[0095] It is not necessary for the information processing device to include all of the components in Fig. 14, and some of the components may be omitted depending on the purpose or conditions of the information processing device. For example, if an interface with a user or operator is not required, the input device 1403 and the output device 1404 may be omitted. If the portable recording medium 1409 is not used, the medium drive device 1406 may be omitted.

[0096] Although the disclosed embodiments and their advantages have been described in detail, it will be appreciated that those skilled in the art may make various modifications, additions and omissions therein without departing from the scope of the invention as clearly set forth in the claims.

[0097] The following supplementary notes are further disclosed regarding the embodiment described with reference to FIGS. (Appendix 1) A quantum computer that calculates the expected value of a computation target using a quantum circuit; an update unit that obtains a specific parameter by performing an update process a predetermined number of times, the update unit obtains the expected value from the quantum computer, updates the parameters of the quantum circuit based on the expected value to obtain updated parameters, and controls the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; An expected value calculation system comprising: (Appendix 2) 2. The expected value calculation system according to claim 1, wherein the calculation unit calculates the expected value using a quantum simulator. (Appendix 3) The expected value calculation system according to claim 1, wherein the calculation unit is a quantum computer having an error correction function. (Appendix 4) The expected value calculation system according to any one of claims 1 to 3, characterized in that the update unit determines, as the specific parameter, the parameter when the expected value obtained from the quantum computer converges. (Appendix 5) The expected value calculation system according to any one of claims 1 to 3, characterized in that the quantum circuit includes a first circuit that generates a quantum state using parameters of the quantum circuit, and a second circuit that calculates the expected value from the quantum state. (Appendix 6) an update unit that obtains specific parameters by performing an update process a predetermined number of times, the update unit acquiring an expected value from a quantum computer that calculates an expected value of a calculation target using a quantum circuit, updating parameters of the quantum circuit based on the expected value to obtain updated parameters, and controlling the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; An expected value calculation device comprising: (Appendix 7) 7. The expected value calculation device according to claim 6, wherein the calculation unit calculates the expected value using a quantum simulator. (Appendix 8) 8. The expected value calculation device according to claim 6 or 7, wherein the update unit determines, as the specific parameter, a parameter when the expected value obtained from the quantum computer converges. (Appendix 9) The expected value calculation device according to claim 6 or 7, wherein the quantum circuit includes a first circuit that generates a quantum state using parameters of the quantum circuit, and a second circuit that calculates the expected value from the quantum state. (Appendix 10) The quantum computer calculates the expected value of the computation target using a quantum circuit, an update unit obtains the expected value from the quantum computer, updates the parameters of the quantum circuit based on the expected value to obtain updated parameters, and controls the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied, performing this update process a predetermined number of times to obtain specific parameters; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; Expected value calculation method. (Appendix 11) 11. The expected value calculation method according to claim 10, wherein the process of calculating the expected value with higher accuracy than the quantum computer includes a process of calculating the expected value using a quantum simulator. (Appendix 12) The expected value calculation method according to claim 10, wherein the calculation unit is a quantum computer having an error correction function. (Appendix 13) 13. The expected value calculation method according to any one of claims 10 to 12, wherein the process of calculating the specific parameter includes a process of calculating, as the specific parameter, a parameter when the expected value obtained from the quantum computer converges. (Appendix 14) 13. The expected value calculation method according to any one of claims 10 to 12, wherein the quantum circuit includes a first circuit that generates a quantum state using parameters of the quantum circuit, and a second circuit that calculates the expected value from the quantum state. [Explanation of symbols]

[0098] 101, 311, 401 Quantum Computers 102 Classical Computers 201 Quantum Simulator 301 Expected Value Calculation System 312, 712 update section 313, 713 calculation section 402 Server 403, 1202 communication lines 501 Ansatz 502 Operator Circuit 503 Measurement circuit 511 Initialization circuit 512 Generation circuit 611 Communication Interface 612 Control device 613 Quantum Systems 711 Communications Department 714 Output section 715 Storage section 721 Parameter 801, 901 dashed line 802, 902 curve 803 Final Value 903, 904 Expected value 1001~1003, 1011~1013 bar 1401 CPU 1402 Memory 1403 Input Device 1404 Output Device 1405 Auxiliary storage device 1406 Media Drive Unit 1407 Network connection device 1408 Bus 1409 Portable recording media

Claims

1. A quantum computer that calculates the expected value of a computation target using a quantum circuit; an update unit that obtains a specific parameter by performing an update process a predetermined number of times, the update unit obtains the expected value from the quantum computer, updates the parameters of the quantum circuit based on the expected value to obtain updated parameters, and controls the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; An expected value calculation system comprising:

2. 2. The expected value calculation system according to claim 1, wherein the calculation unit calculates the expected value using a quantum simulator.

3. 2. The expected value calculation system according to claim 1, wherein the calculation unit is a quantum computer having an error correction function.

4. 4. The expected value calculation system according to claim 1, wherein the update unit determines, as the specific parameter, a parameter when the expected value obtained from the quantum computer has converged.

5. an update unit that obtains specific parameters by performing an update process a predetermined number of times, the update unit acquiring an expected value from a quantum computer that calculates an expected value of a calculation target using a quantum circuit, updating parameters of the quantum circuit based on the expected value to obtain updated parameters, and controlling the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; An expected value calculation device comprising:

6. The quantum computer calculates the expected value of the computation target using a quantum circuit, an update unit obtains the expected value from the quantum computer, updates the parameters of the quantum circuit based on the expected value to obtain updated parameters, and controls the quantum computer to calculate the expected value using the quantum circuit to which the updated parameters have been applied, performing this update process a predetermined number of times to obtain specific parameters; a calculation unit that calculates the expected value with higher accuracy than the quantum computer by using the quantum circuit to which the specific parameters are applied; Expected value calculation method.

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