Approaches for a quantum memory at telecommunication wavelengths

TL;DR

This paper demonstrates experimental quantum storage and retrieval of weak light states at telecommunication wavelengths using erbium-doped solid-state media with two photon echo protocols, advancing solid state quantum memory technology.

Contribution

It introduces and compares two photon echo based protocols, CRIB and AFC, for quantum memory at telecom wavelengths, including phase preservation verification and noise analysis.

Findings

Successful storage and retrieval of weak coherent states.

CRIB protocol enables on-demand retrieval with electric field control.

AFC protocol preserves phase coherence, confirmed by interference experiments.

Abstract

We report experimental storage and retrieval of weak coherent states of light at telecommunication wavelengths using erbium ions doped into a solid. We use two photon echo based quantum storage protocols. The first one is based on controlled reversible inhomogeneous broadening (CRIB). It allows the retrieval of the light on demand by controlling the collective atomic coherence with an external electric field, via the linear Stark effect. We study how atoms in the excited state affect the signal to noise ratio of the CRIB memory. Additionally we show how CRIB can be used to modify the temporal width of the retrieved light pulse. The second protocol is based on atomic frequency combs (AFC). Using this protocol we also verify that the reversible mapping is phase preserving by performing an interference experiment with a local oscillator. These measurements are enabling steps towards solid state quantum memories at telecommunication wavelengths. We also give an outlook on possible improvements.