Integrated bright source of polarization-entangled photons using lithium niobate photonic chips

TL;DR

This paper presents a compact, high-brightness source of polarization-entangled photon pairs on lithium niobate photonic chips, achieving superior generation rates and high entanglement quality, advancing integrated quantum photonics.

Contribution

First demonstration of polarization entanglement on thin film lithium niobate photonic chips with record brightness and high entanglement quality.

Findings

Photon pair generation rate of 508.5 MHz/mW

High entanglement fidelity of 0.944

High purity and concurrence of entangled photon pairs

Abstract

Quantum photonics has rapidly advanced as a key area for developing quantum technologies by harnessing photons' inherent quantum characteristics, particularly entanglement. Generation of entangled photon pairs, known as Bell states, is crucial for quantum communications, precision sensing, and quantum computing. While bulk quantum optical setups have provided foundational progress, integrated quantum photonic platforms now offer superior scalability, efficiency, and integrative potential. In this study, we demonstrate a compact and bright source of polarization-entangled Bell state utilizing continuous-wave pumping on thin film lithium niobate (TFLN) integrated photonics. Our periodically poled lithium niobate device achieves on-chip brightness of photon pair generation rate of 508.5 MHz/mW, surpassing other integrated platforms including silicon photonics. This demonstration marks the first realization of polarization entanglement on TFLN platforms. Experimentally measured metrics confirm high-quality entangled photon pairs with a purity of 0.901, a concurrence of 0.9, and a fidelity of 0.944. We expect our compact quantum devices to have great potential for advancing quantum communication systems and photonic quantum technologies.