Experimental realization of the bucket-brigade quantum random access memory

Fanhao Shen; Yujie Ji; Debin Xiang; Yanzhe Wang; Ke Wang; Chuanyu Zhang; Aosai Zhang; Yiren Zou; Yu Gao; Zhengyi Cui; Gongyu Liu; Jianan Yang; Yihang Han; Jinfeng Deng; Anbang Wang; Zhihong Zhang; Hekang Li; Qiujiang Guo; Pengfei Zhang; Chao Song; Liqiang Lu; Zhen Wang; Jianwei Yin

arXiv · 2506.16682

Experimental realization of the bucket-brigade quantum random access memory

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Abstract

Quantum random access memory (QRAM) enables efficient classical data access for quantum computers -- a prerequisite for many quantum algorithms to achieve quantum speedup. Despite various proposals, the experimental realization of QRAM remains largely unexplored. Here, we experimentally investigate the circuit-based bucket-brigade QRAM with a superconducting quantum processor. To facilitate the experimental implementation, we introduce a hardware-efficient gate decomposition scheme for quantum routers, which effectively reduces the depth of the QRAM circuit by more than 30% compared to the conventional controlled-SWAP-based implementation. We further propose an error mitigation method to boost the QRAM query fidelity. With these techniques, we are able to experimentally implement the QRAM architectures with two and three layers, achieving query fidelities up to 0.800 $\pm$ 0.026 and 0.604$\pm$0.005, respectively. Additionally, we study the error propagation mechanism and the scalability of our QRAM implementation, providing experimental evidence for the noise resilience nature of the bucket-brigade QRAM architecture. Our results highlight the potential of superconducting quantum processors for realizing a scalable QRAM architecture.

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Fanhao Shen, Yujie Ji, Debin Xiang, Yanzhe Wang, Ke Wang, Chuanyu Zhang, Aosai Zhang, Yiren Zou, Yu Gao, Zhengyi Cui, Gongyu Liu, Jianan Yang, Yihang Han, Jinfeng Deng, Anbang Wang, Zhihong Zhang, Hekang Li, Qiujiang Guo, Pengfei Zhang, Chao Song, Liqiang Lu, Zhen Wang, Jianwei Yin. 2025-06-20. Experimental realization of the bucket-brigade quantum random access memory. https://arxiv.org/abs/2506.16682

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