Cutoff phenomenon and entropic uncertainty for random quantum circuits

Article Optics

Comparison of quantum advantage experiments using random circuit sampling

Sangchul Oh et al.

Summary: By comparing the bit strings sampled from classical computers using tensor network simulation with those from the Sycamore quantum processor, it is found that Kalachev et al.'s samples are statistically closer to the Sycamore samples than Pan et al.'s. This finding implies that further study is needed to certify or beat the claims of quantum advantage using random circuit sampling.

PHYSICAL REVIEW A (2023)

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Article Multidisciplinary Sciences

Quantum computational advantage via 60-qubit 24-cycle random circuit sampling

Qingling Zhu et al.

Summary: To maintain a long-term quantum computational advantage, upgrading quantum hardware is necessary to compete against continuously improved classical algorithms and hardware. Researchers have demonstrated a superconducting quantum computing system, Zuchongzhi 2.1, with 66 qubits in a tunable coupler architecture. The improved readout fidelity and more powerful quantum processor enable larger-scale random quantum circuit sampling, enhancing the quantum computational advantage significantly.

SCIENCE BULLETIN (2022)

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Article Chemistry, Physical

Statistical Properties of Bit Strings Sampled from Sycamore Random Quantum Circuits

Sangchul Oh et al.

Summary: This study analyzes the statistical properties of bit strings sampled from Sycamore random circuits and finds that they show stripe patterns at specific qubits and have more bit 1 than 0 compared to classical random bit strings. The calculation of random matrices and Wasserstein distances also reveals that the Sycamore bit strings are farther from bit strings sampled from Haar-measure random quantum circuits than classical random bit strings.

JOURNAL OF PHYSICAL CHEMISTRY LETTERS (2022)

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Article Optics

Statistical analysis on random quantum circuit sampling by Sycamore and Zuchongzhi quantum processors

Sangchul Oh et al.

Summary: The statistical properties of the outputs of random quantum circuit sampling by the Sycamore and Zuchongzhi processors are analyzed and compared. While both processors score similar values of linear cross-entropy fidelity for random circuit sampling, the statistical properties of Sycamore bit strings are quite different from those of Zuchongzhi bit strings. Zuchongzhi bit strings are much closer to classical uniform random bits than those of Sycamore.

PHYSICAL REVIEW A (2022)

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Article Physics, Multidisciplinary

Strong Quantum Computational Advantage Using a Superconducting Quantum Processor

Yulin Wu et al.

Summary: In this study, a two-dimensional programmable superconducting quantum processor named "Zuchongzhi" with 66 functional qubits was developed and used for random quantum circuits sampling to demonstrate quantum computational advantage. The high-precision and programmable quantum computing platform showed exponential outpacing of classical hardware and algorithmic improvements.

PHYSICAL REVIEW LETTERS (2021)

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Article Optics

Optimized entropic uncertainty relations for multiple measurements

Bo-Fu Xie et al.

Summary: The paper improved the lower bound of the entropic uncertainty relation for multiple measurements and proposed a tighter Simply Constructed Bound (SCB), which was optimized by considering mutual information and the Holevo quantity. The proposed bounds extrapolate the behavior of two measurements to a larger collection and are believed to shed light on entropy-based uncertainty relations and benefit security analysis in quantum key distributions.

PHYSICAL REVIEW A (2021)

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Article Optics