Topologically Protecting Squeezed Light on a Photonic Chip

TL;DR

This paper demonstrates topologically protected generation of squeezed light on a silica photonic chip, enhancing quantum photonics by reducing imperfections and crosstalk in integrated systems.

Contribution

It introduces a topological approach to protect nonlinear quantum processes, enabling robust squeezed light generation on a chip with high fidelity.

Findings

Successful experimental demonstration of topologically protected four-wave mixing

High-fidelity measurement of non-classical squeezed states

Verification of protection against fabrication imperfections

Abstract

Squeezed light is a critical resource in quantum sensing and information processing. Due to the inherently weak optical nonlinearity and limited interaction volume, considerable pump power is typically needed to obtain efficient interactions to generate squeezed light in bulk crystals. Integrated photonics offers an elegant way to increase the nonlinearity by confining light strictly inside the waveguide. For the construction of large-scale quantum systems performing many-photon operations, it is essential to integrate various functional modules on a chip. However, fabrication imperfections and transmission crosstalk may add unwanted diffraction and coupling to other photonic elements, reducing the quality of squeezing. Here, by introducing the topological phase, we experimentally demonstrate the topologically protected nonlinear process of spontaneous four-wave mixing enabling the generation of squeezed light on a silica chip. We measure the cross-correlations at different evolution distances for various topological sites and verify the non-classical features with high fidelity. The squeezing parameters are measured to certify the protection of cavity-free, strongly squeezed states. The demonstration of topological protection for squeezed light on a chip brings new opportunities for quantum integrated photonics, opening novel approaches for the design of advanced multi-photon circuits.