Storage of Telecom-Band Time-Bin Qubits in Thin-Film Lithium Niobate

Abstract Integrated photonics has emerged as a promising platform for quantum communication and quantum computation. Thin-film lithium niobate (TFLN) has gained significant attention in this field due to its exceptional optical properties, enabling the realization of numerous integrated photonic devices. However, quantum memory, which serves as a universal building block for the quantum internet, has not yet been demonstrated in TFLN. In this study, we realized the on-chip quantum memory using erbium ions (Er3+) doped TFLN. The developed quantum memory achieves a storage time of 400 ns with an efficiency of 1.95 ± 0.04%, significantly outperforming conventional waveguide delay lines. The multimode capability is demonstrated by successfully storing four temporal modes. Furthermore, single-photon-level coherent pulses are encoded into time-bin qubits and stored with a fidelity of 96.8 ± 0.3%, surpassing the classical limit achievable by the measure-and-prepare strategy. Our results demonstrate the on-chip quantum memory for telecom-band time-bin qubits in Er3+:TFLN, providing a key building block toward integrated quantum registers and repeaters for scalable quantum information processing.