Long-distance atom-photon entanglement

TL;DR

This paper demonstrates entanglement between a single trapped atom and a photon over 300 meters, analyzing coherence and dephasing, advancing the development of long-distance quantum networks.

Contribution

It reports the first observation of remote atom-photon entanglement with coherence verification after fiber transmission and measures atomic dephasing times.

Findings

Successful entanglement over 300 m fiber link

Atomic dephasing time of 150 microseconds

Verification of coherence via local correlation measurements

Abstract

We report the observation of entanglement between a single trapped atom and a single photon at remote locations. The degree of coherence of the entangled atom-photon pair is verified via appropriate local correlation measurements, after communicating the photon via an optical fiber link of 300 m length. In addition we measured the temporal evolution of the atomic density matrix after projecting the atom via a state measurement of the photon onto several well defined spin states. We find that the state of the single atom dephases on a timescale of 150 $\mu$s, which represents an important step toward long-distance quantum networking with individual neutral atoms.