A solid state light-matter interface at the single photon level

TL;DR

This paper demonstrates a coherent, reversible quantum light-matter interface in a solid state medium capable of storing and retrieving single-photon-level light pulses with high fidelity, advancing solid-state quantum memory technology.

Contribution

It presents the first demonstration of a solid-state quantum interface that coherently maps and stores single-photon-level light in a large atomic ensemble, enabling multimode quantum memories.

Findings

Achieved >95% interference visibility, confirming high coherence.

Stored and retrieved light in multiple temporal modes.

Demonstrated collective enhancement at the single photon level.

Abstract

Coherent and reversible mapping of quantum information between light and matter is an important experimental challenge in quantum information science. In particular, it is a decisive milestone for the implementation of quantum networks and quantum repeaters. So far, quantum interfaces between light and atoms have been demonstrated with atomic gases, and with single trapped atoms in cavities. Here we demonstrate the coherent and reversible mapping of a light field with less than one photon per pulse onto an ensemble of 10 millions atoms naturally trapped in a solid. This is achieved by coherently absorbing the light field in a suitably prepared solid state atomic medium. The state of the light is mapped onto collective atomic excitations on an optical transition and stored for a pre-programmed time up of to 1 mu s before being released in a well defined spatio-temporal mode as a result of a collective interference. The coherence of the process is verified by performing an interference experiment with two stored weak pulses with a variable phase relation. Visibilities of more than 95% are obtained, which demonstrates the high coherence of the mapping process at the single photon level. In addition, we show experimentally that our interface allows one to store and retrieve light fields in multiple temporal modes. Our results represent the first observation of collective enhancement at the single photon level in a solid and open the way to multimode solid state quantum memories as a promising alternative to atomic gases.