Validating quantum-supremacy experiments with exact and fast tensor network contraction

Abstract

The quantum supremacy experiment, such as Google Sycamore [Nature \textbf{574}, 505 (2019)], poses great challenge for classical verification due to the exponentially-increasing compute cost. Using a new-generation Sunway supercomputer within $8.5$ days, we provide a direct verification by computing three million exact amplitudes for the experimentally generated bitstrings, obtaining an XEB fidelity of $0.191\%$ (the estimated value is $0.224\%$). The leap of simulation capability is built on a multiple-amplitude tensor network contraction algorithm which systematically exploits the ``classical advantage" (the inherent ``store-and-compute" operation mode of von Neumann machines) of current supercomputers, and a fused tensor network contraction algorithm which drastically increases the compute efficiency on heterogeneous architectures. Our method has a far-reaching impact in solving quantum many-body problems, statistical problems as well as combinatorial optimization problems.

arXiv comment5 pages, 3 figures, comments are welcome!

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Cited by in corpus (10)

• Phase transition in Random Circuit Sampling
• Stabilizer Tensor Networks: universal quantum simulator on a basis of stabilizer states
• Certified randomness using a trapped-ion quantum processor
• The computational power of random quantum circuits in arbitrary geometries
• Tensor networks for quantum computing
• Quantum cryptography beyond key distribution: theory and experiment
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• State of practice: evaluating GPU performance of state vector and tensor network methods
• New quantum codes from homothetic-BCH codes
• Sampling (noisy) quantum circuits through randomized rounding