All-optical switching of photonic entanglement

TL;DR

This paper demonstrates an all-optical switch capable of routing entangled photons at high speed with minimal loss and no measurable impact on entanglement fidelity, advancing quantum network technology.

Contribution

It introduces a novel all-optical switch that preserves entanglement and enables high-speed routing, with potential for encoding multiple qubits on a single photon.

Findings

Achieves 200-ps switching window and 120:1 contrast.

Induces less than 0.002 fidelity degradation in entangled states.

Demonstrates demultiplexing of quantum channels from entangled photon streams.

Abstract

Future quantum optical networks will require the ability to route entangled photons at high speeds, with minimal loss and added in-band noise, and---most importantly---without disturbing the photons' quantum state. Here we present an all-optical switch which fulfills these requirements and characterize its performance at the single photon level. It exhibits a 200-ps switching window, 120:1 contrast, 1.5-dB loss, and induces no measurable degradation in the switched photons' entangled-state fidelity (< 0.002). As a proof-of-principle demonstration of its capability, we use the switch to demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream. Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit quantum states on a single photon.