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  • Open Access

Quantum Storage of Qubits in an Array of Independently Controllable Solid-State Quantum Memories

Markus Teller1,*, Susana Plascencia1, Samuele Grandi1, and Hugues de Riedmatten1,2

  • *Contact author: markus.teller@icfo.eu
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Phys. Rev. X 15, 031053 – Published 25 August, 2025

DOI: https://doi.org/10.1103/z6lc-qw2d

Abstract

Random-access quantum memories may offer computational advantages for quantum computers and networks. In this paper, we advance arrays of solid-state quantum memories toward their usage as random-access quantum memory. We perform quantum storage of path and time-bin qubits implemented with weak coherent states at the single-photon level, in an array of ten temporally multiplexed memory cells with controllable addressing. The qubits can be stored in arbitrary combinations of memory cells, from which they are read out on demand. We find average fidelities of 95−2+2% for path qubits and 91−2+2% for time-bin qubits. The measured fidelities violate the classical bounds for both encodings and for all ten cells. We also sequentially store a time-bin qubit in two different memory cells, maintain both qubits simultaneously in the array, and perform a collective readout. The individual control paired with high storage fidelity represents a significant advance toward a solid-state random-access quantum memory for quantum repeaters and photonic quantum processors.

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Popular Summary

Classical computers use random-access memory to temporarily store information for later processing. Similarly, photonic quantum processors could benefit from a quantum version of RAM to hold quantum information, particularly as they generate and process entangled cluster states one photon at a time. A random-access quantum memory would enable flexible storage of these photons until the quantum state grows large enough for computation. In this work, we move a step closer to this vision by demonstrating quantum storage in an array of individually controlled quantum memories.

Our setup uses a rare-earth ion-doped crystal cooled in a cryostat and paired with two acoustic-optical deflectors to create an array of ten independently addressable quantum memory cells. These cells store quantum bits, or qubits, encoded in either the path or time parameter. Using weak laser pulses at the single-photon level, we assess the performance of the memory array and find that all ten cells violate classical benchmarks, confirming they operate in the quantum regime. Additionally, we successfully store two sequential time-bin qubits and retrieve them simultaneously, showing the system’s ability to handle more complex quantum information storage and retrieval tasks.

Looking forward, improved memory efficiency could allow this array to be integrated with photonic cluster-state sources, forming the basis for scalable quantum computing. The demonstrated control over individual memory cells would also support advanced operations such as collective measurements or selective, sequential readout of quantum states.

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Outline

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Phys. Rev. X 15, 031053– Published 25 August, 2025
  • Received 27 February 2025
  • Revised 13 June 2025
  • Accepted 8 July 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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