Ultrabright Polarization-Entangled Photon Pair Source for Frequency-Multiplexed Quantum Communication in Free-Space

TL;DR

This paper presents an ultrabright, wavelength-optimized polarization-entangled photon source designed for efficient long-distance free-space quantum communication via satellites, utilizing spectral correlations to overcome detector limitations.

Contribution

It introduces a novel, space-ready entangled photon source that leverages hyper-entanglement for wavelength multiplexing, enhancing long-distance satellite-based quantum networks.

Findings

Achieves high pair emission rates exceeding detector bandwidth

Utilizes spectral correlations for efficient wavelength demultiplexing

Demonstrates potential for broadband satellite quantum communication

Abstract

The distribution of entanglement via satellite links will drastically extend the reach of quantum networks. Highly efficient entangled photon sources are an essential requirement towards overcoming high channel loss and achieving practical transmission rates in long-distance satellite downlinks. Here we report on an ultrabright entangled photon source that is optimized for long-distance free-space transmission. It operates in a wavelength range that is efficiently detected with space-ready single photon avalanche diodes (Si-SPADs), and readily provides pair emission rates that exceed the detector bandwidth (i.e., the temporal resolution). To overcome this limitation, we demultiplex the photon flux into wavelength channels that can be handled by current single photon detector technology. This is achieved efficiently by using the spectral correlations due to hyper-entanglement in polarization and frequency as an auxiliary resource. Combined with recent demonstrations of space-proof source prototypes, these results pave the way to a broadband long-distance entanglement distribution network based on satellites.