On-chip generation of heralded photon-number states

Abstract

Quantum photonics is a thriving field of research, investigating fundamental quantum phenomena as well as a variety of disruptive quantum technologies. In this framework, integrated-optic technologies permit the realization of complex and scalable quantum circuits, finding striking repercussions in quantum sensing, teleportation-based communication, as well as in quantum computation and simulation, otherwise unreachable using bulk approaches. Beyond the use of genuine monolithic platforms, we exploit a hybrid strategy enabling, for the first time, on-chip generation of configurable heralded two-photon states. Through real-time device manipulation capabilities, a variety of path-coded heralded two-photon states can be produced, ranging from product to entangled states. Those states are engineered with high levels of purity, assessed by fidelities of 99.5\(\pm\)% and 95.0\(\pm\)8%, respectively, obtained via interferometric measurements. Our strategy therefore stands as a milestone for further exploiting entanglement-based protocols, relying on engineered quantum states, and enabled by scalable and compatible photonic circuits.