On-chip transverse-mode entangled photon pair source

TL;DR

This paper demonstrates an on-chip source of transverse-mode entangled photon pairs using silicon waveguides, achieving high fidelity and bandwidth, enabling advanced quantum photonic applications with multiple degrees of freedom.

Contribution

It introduces a novel integrated source of transverse-mode entangled photons with high fidelity, expanding the capabilities of quantum photonics in silicon platforms.

Findings

Verified transverse-mode photon pairs over 2 THz bandwidth.

Produced a maximally entangled Bell state with 0.96 fidelity.

Showed potential for converting entanglement to other degrees of freedom.

Abstract

Integrated entangled photon pair source is an essential resource for both fundamental investigations and practical applications of quantum information science. Currently there have been several types of entanglement, among which the transverse-mode entanglement is becoming attractive because of its unique advantages. Here, we report an on-chip transverse-mode entangled photon pair source via the spontaneous four-wave mixing processes in a multimode silicon waveguide. Transverse-mode photon pairs are verified over multiple frequency channels within a bandwidth of $\sim$2~THz, and a maximally entangled Bell state is also produced with a net fidelity of $0.96\pm0.01$. Our entangled photon pair source is the key element for quantum photonics based on transverse-mode, and also has the possibility to extend to higher-dimensional Hilbert space. Furthermore, the transverse-mode entanglement can be converted coherently to path and polarization entanglement, which paves the way to realizing highly complex quantum photonic circuits with multiple degrees of freedom.