Near perfect two-photon interference out a down-converter on a silicon photonic chip

TL;DR

This paper demonstrates a silicon-based integrated source of entangled photon pairs with near-perfect two-photon interference, advancing scalable quantum photonic technologies.

Contribution

First implementation of an energy-time entangled photon-pair source using spontaneous parametric down-conversion in silicon with high visibility interference.

Findings

Coincidence-to-accidental ratio of 1635 at 8 μW pump power

Two-photon interference visibility of 99.36%

High-quality entanglement without excess noise

Abstract

Integrated entangled photon-pair sources are key elements for enabling large-scale quantum photonic solutions, and addresses the challenges of both scaling-up and stability. Here we report the first demonstration of an energy-time entangled photon-pair source based on spontaneous parametric down-conversion in silicon-based platform through an optically induced second-order ($\chi^{(2)}$) nonlinearity, ensuring type-0 quasi-phase-matching of fundamental harmonic and its second-harmonic inside the waveguide. The developed source shows a coincidence-to-accidental ratio of 1635 at 8 of $\mu$W pump power. Remarkably, we report two-photon interference with near-perfect visibility of 99.36$\pm1.94\%$, showing high-quality photonic entanglement without excess background noise. This opens a new horizon for quantum technologies requiring the integration of a large variety of building functionalities on single chips.