Optical storage for 0.53 seconds in a solid-state atomic frequency comb memory using dynamical decoupling

TL;DR

This paper demonstrates a significant increase in quantum memory storage time from milliseconds to over half a second in a solid-state atomic frequency comb memory by applying magnetic fields, spin-echo, and dynamical decoupling techniques.

Contribution

The authors developed a AFC spin-wave memory with extended storage time using magnetic fields and dynamical decoupling, achieving a 530 ms coherence time, surpassing previous limits.

Findings

Achieved 40 ms storage time with a simple spin-echo sequence.

Extended coherence time to 530 ms using dynamical decoupling.

Demonstrated potential for long-duration quantum information storage.

Abstract

Quantum memories with long storage times are key elements in long-distance quantum networks. The atomic frequency comb (AFC) memory in particular has shown great promise to fulfill this role, having demonstrated multimode capacity and spin-photon quantum correlations. However, the memory storage times have so-far been limited to about one millisecond, realized in a Eu${}^{3+}$ doped Y${}_2$SiO${}_5$ crystal at zero applied magnetic field. Motivated by studies showing increased spin coherence times under applied magnetic field, we developed a AFC spin-wave memory utilizing a weak 15 mT magnetic field in a specific direction that allows efficient optical and spin manipulation for AFC memory operations. With this field configuration the AFC spin-wave storage time increased to 40 ms using a simple spin-echo sequence. Furthermore, by applying dynamical decoupling techniques the spin-wave coherence time reaches 530 ms, a 300-fold increase with respect to previous AFC spin-wave storage experiments. This result paves the way towards long duration storage of quantum information in solid-state ensemble memories.