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Solving the Sampling Problem of the Sycamore Quantum Circuits

Feng Pan, Keyang Chen, and Pan Zhang
Phys. Rev. Lett. 129, 090502 – Published 22 August 2022
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Abstract

We study the problem of generating independent samples from the output distribution of Google’s Sycamore quantum circuits with a target fidelity, which is believed to be beyond the reach of classical supercomputers and has been used to demonstrate quantum supremacy. We propose a method to classically solve this problem by contracting the corresponding tensor network just once, and is massively more efficient than existing methods in generating a large number of uncorrelated samples with a target fidelity. For the Sycamore quantum supremacy circuit with 53 qubits and 20 cycles, we have generated 1×106 uncorrelated bitstrings s which are sampled from a distribution P^(s)=|ψ^(s)|2, where the approximate state ψ^ has fidelity F0.0037. The whole computation has cost about 15 h on a computational cluster with 512 GPUs. The obtained 1×106 samples, the contraction code and contraction order are made public. If our algorithm could be implemented with high efficiency on a modern supercomputer with ExaFLOPS performance, we estimate that ideally, the simulation would cost a few dozens of seconds, which is faster than Google’s quantum hardware.

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  • Received 20 November 2021
  • Accepted 20 July 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.090502

© 2022 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

Feng Pan1,2, Keyang Chen1,3, and Pan Zhang1,4,5,*

  • 1CAS Key Laboratory for Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Yuanpei College, Peking University, Beijing 100871, China
  • 4School of Fundamental Physics and Mathematical Sciences, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310024, China
  • 5International Centre for Theoretical Physics Asia-Pacific, Beijing/Hangzhou, China

  • *panzhang@itp.ac.cn

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Issue

Vol. 129, Iss. 9 — 26 August 2022

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