Long-time storage of a decoherence-free subspace logical qubit in a dual-type quantum memory

Y. L. Xu; L. Zhang; C. Zhang; Y. K. Wu; Y. Y. Chen; C. X. Huang; Z. B. Cui; R. Yao; W. Q. Lian; J. Y. Ma; W. X. Guo; B. X. Qi; P. Y. Hou; Y. F. Pu; Z. C. Zhou; L. He; L. M. Duan

arXiv · 2507.13320

Long-time storage of a decoherence-free subspace logical qubit in a dual-type quantum memory

Y. L. Xu·L. Zhang·C. Zhang·Y. K. Wu·Y. Y. Chen·C. X. Huang·Z. B. Cui·R. Yao·W. Q. Lian·J. Y. Ma·W. X. Guo·B. X. Qi·P. Y. Hou·Y. F. Pu·Z. C. Zhou·L. He·L. M. Duan

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Abstract

A quantum memory is an essential element for quantum computation, quantum network and quantum metrology. Previously, a single-qubit quantum memory with a coherence time of about an hour has been realized in a dual-species setup where a coolant ion provides sympathetic cooling for a memory ion of different species. However, the frequent random position hopping between the ions in the room-temperature trap limits the technique there only applicable to single-qubit storage. Here we report a multi-ion quantum memory in a cryogenic trap based on the dual-type scheme, and demonstrate a coherence time above two hours for a logical qubit encoded in the decoherence-free subspace, i.e. two-ion entangled states, after correcting the dominant leakage error. Our scheme alleviates the necessity of an ultra-stable frequency reference for the stored qubit, and has a preferable scalability owing to the same mass of the metastable-state memory ions and the ground-state coolant ion.

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Y. L. Xu, L. Zhang, C. Zhang, Y. K. Wu, Y. Y. Chen, C. X. Huang, Z. B. Cui, R. Yao, W. Q. Lian, J. Y. Ma, W. X. Guo, B. X. Qi, P. Y. Hou, Y. F. Pu, Z. C. Zhou, L. He, L. M. Duan. 2025-07-17. Long-time storage of a decoherence-free subspace logical qubit in a dual-type quantum memory. https://arxiv.org/abs/2507.13320

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