Entanglement Assisted Non-local Optical Interferometry in a Quantum Network

The sensitivity of non-local optical measurements at low light intensities, such as those involved in long baseline telescope arrays, can be improved by using remote entanglement. Here, we demonstrate the use of entangled quantum memories in a quantum network of Silicon-vacancy centers in diamond nano-cavities to experimentally perform such non-local phase measurements. Specifically, we combine the generation of event-ready remote quantum entanglement, photon mode erasure that hides the "which-path" information of temporally and spatially separated incoming optical modes, and non-local, non-destructive photon heralding enabled by remote entanglement to perform a proof-of-concept entanglement-assisted differential phase measurement of weak incident light between two spatially separate stations. Demonstrating successful operation of the remote phase sensing protocol with a fiber link baseline up to 1.55 km, our results open the door for a new class of quantum enhanced imaging applications.