Quantum memory for entangled two-mode squeezed states

TL;DR

This paper demonstrates a room-temperature quantum memory capable of storing entangled two-mode squeezed states with preserved quantum coherence, advancing the development of quantum information networks.

Contribution

It introduces a quantum memory for EPR-entangled states with verified quantum coherence and a 1 ms storage time using cesium atoms at room temperature.

Findings

Memory fidelity of 0.52 exceeds classical benchmark of 0.45

Successfully stored and preserved EPR entanglement

Memory operates at room temperature with 1 ms duration

Abstract

A quantum memory for light is a key element for the realization of future quantum information networks. Requirements for a good quantum memory are (i) versatility (allowing a wide range of inputs) and (ii) true quantum coherence (preserving quantum information). Here we demonstrate such a quantum memory for states possessing Einstein-Podolsky-Rosen (EPR) entanglement. These multi-photon states are two-mode squeezed by 6.0 dB with a variable orientation of squeezing and displaced by a few vacuum units. This range encompasses typical input alphabets for a continuous variable quantum information protocol. The memory consists of two cells, one for each mode, filled with cesium atoms at room temperature with a memory time of about 1msec. The preservation of quantum coherence is rigorously proven by showing that the experimental memory fidelity 0.52(2) significantly exceeds the benchmark of 0.45 for the best possible classical memory for a range of displacements.