Curator's Take
This breakthrough represents a crucial step toward building practical quantum internet infrastructure by demonstrating the first on-chip quantum memory in thin-film lithium niobate, a material that has become increasingly important for integrated quantum photonics. The ability to store telecom-band qubits with 96.8% fidelity while maintaining quantum coherence addresses one of the key bottlenecks in quantum communication networks, where quantum memories are essential for synchronizing photons and enabling quantum repeaters. What makes this particularly significant is the integration on a TFLN chip, which offers exceptional optical properties and could enable mass production of quantum memory devices using existing semiconductor fabrication techniques. While the 400 nanosecond storage time and 1.95% efficiency still need improvement for practical applications, this work establishes TFLN as a viable platform for the quantum memory components that will be critical for scaling quantum networks beyond laboratory demonstrations.
— Mark Eatherly
Summary
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 first on-chip quantum memory using erbium ions doped TFLN. The developed quantum memory achieves a storage time of 400 ns with an efficiency of 1.95%, 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% , surpassing the classical limit achievable by measure-and-prepare strategy. Our results demonstrate the first on-chip quantum memory for telecom-band time-bin qubits in TFLN, providing a key building block toward integrated quantum registers and repeaters for scalable quantum information processing.