Coherent Optical Memory with High Storage Efficiency and Large Fractional Delay

TL;DR

This paper demonstrates a highly efficient and long-lived optical quantum memory using cold atomic media with record fractional delay and high fidelity, advancing quantum communication technology.

Contribution

It reports a 78% storage efficiency and a record fractional delay of 74 in EIT-based optical memory, with high phase coherence suitable for quantum applications.

Findings

78% light pulse storage efficiency achieved

Fractional delay of 74 recorded, best to date

Classical fidelity over 90%, stable over storage time

Abstract

A high-storage efficiency and long-lived quantum memory for photons is an essential component in long-distance quantum communication and optical quantum computation. Here, we report a 78% storage efficiency of light pulses in a cold atomic medium based on the effect of electromagnetically induced transparency (EIT). At 50% storage efficiency, we obtain a fractional delay of 74, which is the best up-to-date record. The classical fidelity of the recalled pulse is better than 90% and nearly independent of the storage time, as confirmed by the direct measurement of phase evolution of the output light pulse with a beat-note interferometer. Such excellent phase coherence between the stored and recalled light pulses suggests that the current result can be readily applied to single photon wave packets. Our work significantly advances the technology of EIT-based optical memory and may find practical applications in long-distance quantum communication and optical quantum computation.