A monolithically integrated polarization entangled photon pair source on a silicon chip

TL;DR

This paper presents the first integrated silicon chip that generates polarization-entangled photon pairs with high fidelity, advancing scalable quantum photonic technologies.

Contribution

It introduces a monolithically integrated polarization-entangled photon pair source on a silicon chip, enabling scalable quantum information processing.

Findings

Achieved 91% fidelity in entangled photon pair generation.

Implemented a stable silicon-on-insulator photonic circuit.

Provided versatile interfaces for polarization manipulation.

Abstract

Integrated photonic circuits are one of the most promising platforms for large-scale photonic quantum information systems due to their small physical size and stable interferometers with near-perfect lateral-mode overlaps. Since many quantum information protocols are based on qubits defined by the polarization of photons, we must develop integrated building blocks to generate, manipulate, and measure the polarization-encoded quantum state on a chip. The generation unit is particularly important. Here we show the first integrated polarization-entangled photon pair source on a chip. We have implemented the source as a simple and stable silicon-on-insulator photonic circuit that generates an entangled state with 91 \pm 2% fidelity. The source is equipped with versatile interfaces for silica-on-silicon or other types of waveguide platforms that accommodate the polarization manipulation and projection devices as well as pump light sources. Therefore, we are ready for the full-scale implementation of photonic quantum information systems on a chip.