Entangling Color-Different Photons via Time-Resolved Measurement and Active Feed-Forward

TL;DR

This paper demonstrates the first entanglement of color-different photons using time-resolved measurement and active feed-forward, overcoming frequency mismatch issues for quantum networks.

Contribution

It introduces a novel method combining time-resolved measurement and active feed-forward to entangle photons of different colors, with successful experimental validation.

Findings

Entangled photons with 16 times larger frequency separation than linewidths.

Identified varying entanglement in different two-photon temporal modes.

Converted varying entanglement into uniform using active feed-forward.

Abstract

Entangling independent photons is not only of fundamental interest but also of crucial importance for quantum information science. Two-photon interference is a major method to entangle independent identical photons. If two photons are color-different, perfect two-photon coalescence cannot happen anymore, which makes the entangling of color-different photons difficult to realize. In this letter by exploring and developing time-resolved measurement and active feed-forward, we have entangled two independent photons of different colors for the first time. We find that entanglement with a varying form can be identified for different two-photon temporal modes through time-resolved measurement. By using active feed-forward we are able to convert the varying entanglement into uniform. Adopting these measures, we have successfully entangled two photons with a frequency separation of 16 times larger than their linewidths. In addition to its fundamental interest, our work also provides an approach to solve the frequency mismatch problem for future quantum networks.