Quantum interface between light and atomic ensembles

TL;DR

This paper reviews the development of quantum interfaces between light and atomic ensembles, highlighting mechanisms, experimental techniques, and key experiments in quantum memory, entanglement, and teleportation, emphasizing their role in quantum information processing.

Contribution

It provides a comprehensive theoretical and experimental overview of quantum light-atom interfaces, including mechanisms, techniques, and recent experimental achievements.

Findings

Demonstrated quantum memory for light

Achieved entanglement between light and atomic ensembles

Realized quantum teleportation with atomic ensembles

Abstract

During the past decade the interaction of light with multi-atom ensembles has attracted a lot of attention as a basic building block for quantum information processing and quantum state engineering. The field started with the realization that optically thick free space ensembles can be efficiently interfaced with quantum optical fields. By now the atomic ensemble - light interfaces have become a powerful alternative to the cavity-enhanced interaction of light with single atoms. We discuss various mechanisms used for the quantum interface, including quantum nondemolition or Faraday interaction, quantum measurement and feedback, Raman interaction and electromagnetically induced transparency. The paper provides a common theoretical frame for these processes, describes basic experimental techniques and media used for quantum interfaces, and reviews several key experiments on quantum memory for light, quantum entanglement between atomic ensembles and light, and quantum teleportation with atomic ensembles. We discuss the two types of quantum measurements which are most important for the interface: homodyne detection and photon counting. The paper concludes with an outlook on the future of atomic ensembles as an enabling technology in quantum information processing.