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EP-4742116-A1 - QUANTUM COMPUTING PROGRAM, QUANTUM COMPUTING METHOD, AND INFORMATION PROCESSING DEVICE

EP4742116A1EP 4742116 A1EP4742116 A1EP 4742116A1EP-4742116-A1

Abstract

To reduce errors caused by various types of noise. An information processing apparatus (10) obtains a plurality of equivalent circuits (2a, 2b, and so on), which is equivalent to a two-qubit gate (1a to 1f) included in a first quantum circuit (1) and is generated using respective ones of a plurality of MS gates (3a, 3b, and so on) whose parameter values differ. The information processing apparatus (10) generates a plurality of second quantum circuits (4a, 4b, and so on) by converting the two-qubit gate (1a to 1f) included in the first quantum circuit (1) into each of the equivalent circuits (2a, 2b, and so on). The information processing apparatus (10) causes a quantum computer to execute quantum computations respectively in accordance with the generated second quantum circuits (4a, 4b, and so on). Then, the information processing apparatus (10) outputs, as a computation result of the first quantum circuit (1), a value obtained by averaging results of the quantum computations executed respectively in accordance with the second quantum circuits (4a, 4b, and so on).

Inventors

  • ISHII, MASATOSHI

Assignees

  • FUJITSU LIMITED

Dates

Publication Date
20260513
Application Date
20230703

Claims (7)

  1. A quantum computation program that causes a computer to execute a process comprising: obtaining a plurality of equivalent circuits, the plurality of equivalent circuits being equivalent to a two-qubit gate included in a first quantum circuit and being generated using respective ones of a plurality of Mølmer-Sørenson (MS) gates whose parameter values differ; generating a plurality of second quantum circuits by converting the two-qubit gate included in the first quantum circuit into each of the plurality of equivalent circuits; causing a quantum computer to execute quantum computations respectively in accordance with the plurality of second quantum circuits generated; and outputting, as a computation result of the first quantum circuit, a value obtained by averaging results of the quantum computations executed by the quantum computer in accordance with the plurality of second quantum circuits.
  2. The quantum computation program according to claim 1, wherein: the generating of the plurality of second quantum circuits includes, when the two-qubit gate included in the first quantum circuit includes a plurality of two-qubit gates of the same type, generating the plurality of second quantum circuits, in which, for each of the plurality of second quantum circuits, each of the plurality of two-qubit gates is converted into the same one of the plurality of equivalent circuits.
  3. The quantum computation program according to claim 1, wherein: the generating of the plurality of equivalent circuits includes designating, as two or more target candidate-value sequences, candidate-value sequences generable by selecting two times, with duplication allowed, from among a plurality of candidate values that are boundary angles obtained by dividing 360° into n, where n is an integer of 2 or greater, and generating, for each of the two or more target candidate-value sequences, the plurality of equivalent circuits using one of the plurality of MS gates, in which a first candidate value and a second candidate value indicated by the target candidate-value sequence are respectively set as a value of a first parameter and a value of a second parameter.
  4. The quantum computation program according to claim 3, wherein: the generating of the plurality of equivalent circuits includes, among the candidate-value sequences generable, designating, as one of the two or more target candidate-value sequences, one of two candidate-value sequences in which, for each of the two candidate-value sequences, an angle obtained by adding the first candidate value and the second candidate value included in the candidate-value sequence and an angle obtained by subtracting the second candidate value from the first candidate value included in the candidate-value sequence are both equal between the two candidate-value sequences.
  5. The quantum computation program according to claim 1, wherein: the generating of the plurality of equivalent circuits includes randomly generating angles within a range from 0° to 360°, and generating the plurality of equivalent circuits using the respective ones of the plurality of MS gates in which the randomly generated angles are used as the parameter values.
  6. A quantum computation method executed by a computer, the quantum computation method comprising: obtaining a plurality of equivalent circuits, the plurality of equivalent circuits being equivalent to a two-qubit gate included in a first quantum circuit and being generated using respective ones of a plurality of Mølmer-Sørensen (MS) gates whose parameter values differ; generating a plurality of second quantum circuits by converting the two-qubit gate included in the first quantum circuit into each of the plurality of equivalent circuits; causing a quantum computer to execute quantum computations respectively in accordance with the plurality of second quantum circuits generated; and outputting, as a computation result of the first quantum circuit, a value obtained by averaging results of the quantum computations executed by the quantum computer in accordance with the plurality of second quantum circuits.
  7. An information processing apparatus comprising: a processing unit for: obtaining a plurality of equivalent circuits, the plurality of equivalent circuits being equivalent to a two-qubit gate included in a first quantum circuit and being generated using respective ones of a plurality of Mølmer-Sørensen (MS) gates whose parameter values differ, generating a plurality of second quantum circuits by converting the two-qubit gate included in the first quantum circuit into each of the plurality of equivalent circuits, causing a quantum computer to execute quantum computations respectively in accordance with the plurality of second quantum circuits generated, and outputting, as a computation result of the first quantum circuit, a value obtained by averaging results of the quantum computations executed by the quantum computer in accordance with the plurality of second quantum circuits.

Description

Technical Field The present disclosure relates to a quantum computation program, a quantum computation method, and an information processing apparatus. Background Art Currently, available quantum computers are of the type referred to as Noisy Intermediate-Scale Quantum Computers (NISQ), which use superconducting quantum bits (qubits) or ion-trap qubits. In these quantum devices, the error rate is approximately 1%, and the number of qubits is about 10 to 1000. Such small-scale quantum computers are incapable of completely correcting errors. Therefore, when executing quantum computation on a quantum computer, it is important to perform the quantum computation with a quantum circuit that reduces errors as much as possible. In addition, quantum computers are equipped with one-qubit gates and two-qubit gates as quantum gates for operating qubits. These quantum gates are referred to as native gates. Which two-qubit gate is supported as a native gate depends on the type of quantum device adopted in the quantum computer. On the other hand, a quantum circuit constructed for solving a target problem may include quantum gates other than native gates. In such cases, quantum gates other than native gates are converted into equivalent circuits composed of native gates, and are then implemented in a qubit control apparatus that performs gate operations on qubits. For example, a three-qubit gate such as a CCX (Toffoli) gate is implemented using a plurality of two-qubit gates. A CnX gate or a CnZ gate (where n is an integer of 3 or more) having three or more control bits is converted into a plurality of CCX gates and then further converted into native gates. In current NISQ devices, the noise of two-qubit gates is about an order of magnitude greater than that of one-qubit gates. Accordingly, two-qubit gates have a greater impact on the accuracy of quantum computation compared with one-qubit gates. A typical example of such noise is over-rotation noise, which is referred to as coherent noise. Regarding coherent noise, it has been proposed to use randomized compiling (RC) to reduce unpredictable errors attributable to coherent noise. RC converts coherent errors into stochastic noise, substantially reduces unpredictable errors in quantum algorithms, and enables accurate prediction of algorithm performance from error rates measured by cycle benchmarking. Citation List Non-Patent Literature NPTL1: Akel Hashim, Ravi K. Naik, Alexis Morvan, Jean-Loup Ville, Bradley Mitchell, John Mark Kreikebaum, Marc Davis, Ethan Smith, Costin Iancu, Kevin P. O'Brien, Ian Hincks, Joel J. Wallman, Joseph Emerson, Irfan Siddiqi, "Randomized compiling for scalable quantum computing on a noisy superconducting quantum processor", arXiv:2010.00215v2, 12 May 2021 Summary of Invention Technical Problem RC is effective for reducing errors arising from over-rotation noise (quantum error mitigation); however, RC is not effective for other types of noise. In practical quantum computation performed by a quantum computer, various types of noise occur. Accordingly, there is a need for a quantum error mitigation technique that reduces errors even in practical quantum computation in which various types of noise are present. In one aspect, the present disclosure is directed to reducing errors attributable to various types of noise. Solution to Problem In one aspect, a quantum computation program is provided that causes a computer to execute the following processing. The computer obtains a plurality of equivalent circuits, the plurality of equivalent circuits being equivalent to a two-qubit gate included in a first quantum circuit and being generated using respective ones of a plurality of Mølmer-Sørenson (MS) gates whose parameter values differ. The computer generates a plurality of second quantum circuits by converting the two-qubit gate included in the first quantum circuit into each of the plurality of equivalent circuits. The computer causes a quantum computer to execute quantum computations respectively in accordance with the plurality of second quantum circuits generated. The computer outputs, as a computation result of the first quantum circuit, a value obtained by averaging results of the quantum computations executed by the quantum computer in accordance with the plurality of second quantum circuits. Advantageous Effects of Invention In one aspect, errors attributable to various types of noise are reduced. The above and other objects, features, and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, which illustrate preferred embodiments of the present invention by way of example. Brief Description of Drawings FIG. 1 illustrates an example of a quantum computation method according to a first embodiment.FIG. 2 illustrates an example of a configuration of a quantum computation system.FIG. 3 illustrates an example of a hardware configuration of a quantum computer device