Light-matter entanglement for hybrid quantum networks

Abstract

This research aims to establish a key element of hybrid quantum networks by demonstrating remote entanglement between disparate quantum systems, specifically a cold atomic ensemble and a rare-earth ion-doped crystal, on a long-term project. In this work, we focused on two important aspects towards this goal: the development of a qubit converter and quantum frequency conversion techniques. The qubit converter is built to transform polarization qubits from the cold atoms system into time-bin qubits to ensure compatibility with photons from the solid-state system. Then, quantum frequency conversion based on non-linear effects is studied to shift the 780nm entangled photon of the atomic system to the telecom C-band, aligning it with photons from the rare-earth ion-doped crystal experiment. This process is essential for conducting the Bell-state measurement required for remote entanglement generation.