A millisecond quantum memory for scalable quantum networks

TL;DR

This paper demonstrates a significant advancement in quantum memory technology by extending the storage time of single excitations to 1 millisecond, crucial for scalable quantum networks.

Contribution

The authors experimentally extended quantum memory storage time for single excitations to 1 ms using clock states and long-wavelength spin waves, surpassing previous limits.

Findings

Achieved 1 ms storage time for quantum memory of single excitations.

Identified mechanisms of decoherence in atomic ensemble quantum memories.

Utilized clock states and long-wavelength spin waves to suppress dephasing.

Abstract

Scalable quantum information processing critically depends on the capability of storage of a quantum state. In particular, a long-lived storable and retrievable quantum memory for single excitations is of crucial importance to the atomic-ensemble-based long-distance quantum communication. Although atomic memories for classical lights and continuous variables have been demonstrated with milliseconds storage time, there is no equal advance in the development of quantum memory for single excitations, where only around 10 $\mu$s storage time was achieved. Here we report our experimental investigations on extending the storage time of quantum memory for single excitations. We isolate and identify distinct mechanisms for the decoherence of spin wave (SW) in atomic ensemble quantum memories. By exploiting the magnetic field insensitive state, ``clock state", and generating a long-wavelength SW to suppress the dephasing, we succeed in extending the storage time of the quantum memory to 1 ms. Our result represents a substantial progress towards long-distance quantum communication and enables a realistic avenue for large-scale quantum information processing.