A lithium-niobate chip stores quantum signals in four time slots

The device held telecom-band time-bin qubits for 400 nanoseconds and recovered them with 96.8% fidelity.

Editorial illustration — not from the study.

The study demonstrated a quantum memory made from erbium ions in thin-film lithium niobate, an integrated optical material. The device stored incoming signals for 400 nanoseconds, with a storage efficiency of 1.95 ± 0.04%, and held four separate temporal modes.

The researchers also encoded single-photon-level coherent pulses as time-bin qubits—quantum information represented by different arrival times. The retrieved qubits had a fidelity of 96.8 ± 0.3%, higher than the classical limit for a measure-and-prepare strategy.

What the chip stored

The erbium-doped thin-film lithium-niobate device functioned as an on-chip quantum memory. It stored signals for 400 nanoseconds with an efficiency of 1.95 ± 0.04%, and it stored four temporal modes. Telecom-band time-bin qubits encoded in single-photon-level coherent pulses were recovered with a fidelity of 96.8 ± 0.3%, exceeding the classical measure-and-prepare limit.

Why the memory matters

Quantum memories are used to temporarily store quantum information and are a proposed building block for quantum communication networks and processors. Demonstrating this function in thin-film lithium niobate adds a memory component to an integrated photonics platform already used for other optical devices, supporting the development of integrated quantum registers and repeaters.

Evidence and limits

The evidence comes from an experimental demonstration reported in a research article in ACS Photonics. The device was tested with four temporal modes and single-photon-level coherent pulses, rather than a full quantum network. Its reported storage time was 400 nanoseconds and its efficiency was 1.95%, so the abstract does not establish long storage times, high-efficiency operation or scalability beyond the demonstrated conditions.

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