All-Optical Routing of Single Photons by a One-Atom Switch Controlled by a Single Photon

TL;DR

This paper demonstrates an all-optical single-photon switch using a single atom coupled to a microresonator, enabling routing of photons with high efficiency and minimal control photons, advancing quantum network technology.

Contribution

It presents the first realization of a single-photon activated all-optical switch using a single atom and fiber-coupled microresonator, compatible with scalable quantum architectures.

Findings

Switch toggles from 65% reflection to 90% transmission.

Average control photons per switch event is ~1.5.

Device operates with in-fiber, identical control and target photons.

Abstract

The prospect of quantum networks, in which quantum information is carried by single photons in photonic circuits, has long been the driving force behind the effort to achieve all-optical routing of single photons. Here we realize the most basic unit of such a photonic circuit: a single-photon activated switch, capable of routing a photon from any of its two inputs to any of its two outputs. Our device is based on a single 87Rb atom coupled to a fiber-coupled, chip-based microresonator, and is completely all-optical, requiring no other fields beside the in-fiber single-photon pulses. Nonclassical statistics of the control pulse confirm that a single reflected photon toggles the switch from high reflection (65%) to high transmission (90%), with average of ~1.5 control photons per switching event (~3 including linear losses). The fact that the control and target photons are both in-fiber and practically identical makes this scheme compatible with scalable architectures for quantum information processing.