Topological Protection of Two-photon Quantum Correlation on a Photonic Chip

TL;DR

This paper demonstrates experimentally that topological boundary states on a photonic chip can protect two-photon quantum correlations from decoherence, showing high cross-correlation and violation of classical inequalities, advancing quantum topological photonics.

Contribution

It provides the first experimental demonstration of topological protection of two-photon quantum states on a photonic chip, combining topological photonics with quantum information.

Findings

High quantum correlation preserved in topological boundary states

Strong violation of Cauchy-Schwarz inequality up to 30 standard deviations

Potential for scalable quantum information processing using topological protection

Abstract

Low-decoherence regime plays a key role in constructing multi-particle quantum systems and has therefore been constantly pursued in order to build quantum simulators and quantum computers in a scalable fashion. Quantum error correction and quantum topological computing have been proved being able to protect quantumness but haven't been experimentally realized yet. Recently, topological boundary states are found inherently stable and are capable of protecting physical fields from dissipation and disorder, which inspires the application of such a topological protection on quantum correlation. Here, we present an experimental demonstration of topological protection of two-photon quantum states on a photonic chip. By analyzing the quantum correlation of photons out from the topologically nontrivial boundary state, we obtain a high cross-correlation and a strong violation of Cauchy-Schwarz inequality up to 30 standard deviations. Our results, together with our integrated implementation, provide an alternative way of protecting quantumness, and may inspire many more explorations in 'quantum topological photonics', a crossover between topological photonics and quantum information.