Researchers have made significant advancements in quantum technology by successfully demonstrating integrated spin-wave quantum memory, addressing longstanding issues related to noise and storage capacity. This development is crucial for establishing large-scale quantum networks that connect short-distance entanglements into longer ones, effectively mitigating photon transmission losses. Traditional quantum memories have had limitations due to reliance on optically excited states, which restrict on-demand retrieval and are bound by the state lifetimes. The new spin-wave storage technique allows for on-demand retrieval and extended storage times by converting photons into spin-wave excitations in ground states.
The research conducted by Chuan-Feng Li’s team at the University of Science and Technology of China involved creating a circularly-symmetric waveguide in a Eu:YSO crystal, enhancing noise suppression through polarization-based filtering. They successfully implemented two spin-wave storage protocols—modified noiseless photon echo (NLPE) and atomic frequency comb (AFC)—with NLPE achieving over four times the efficiency of AFC. The fidelity of storing and retrieving time-bin qubits was measured at 94.9±1.2%, surpassing limits of classical devices. This breakthrough paves the way for multiplexed quantum repeaters and advanced quantum memory systems.
