Non-Abelian braiding on photonic chips

TL;DR

This paper demonstrates the first on-chip photonic system capable of non-Abelian braiding of multiple modes, using geometric phases in waveguide arrays, with potential applications in quantum information processing.

Contribution

It presents the experimental realization of non-Abelian braiding on photonic chips, a significant step towards photonic quantum computing and topological photonics.

Findings

Successful on-chip non-Abelian braiding of five photonic modes

Sequence-dependent photon swapping observed in classical and quantum regimes

Photonic platform is versatile and expandable for non-Abelian physics studies

Abstract

Non-Abelian braiding has attracted significant attention because of its pivotal role in describing the exchange behaviors of anyons--a candidate for realizing quantum logics. The input and outcome of non-Abelian braiding are connected by a unitary matrix which can also physically emerge as a geometric-phase matrix in classical systems. Hence it is predicted that non-Abelian braiding should have analogues in photonics, but a feasible platform and the experimental realization remain out of reach. Here, we propose and experimentally realize an on-chip photonic system that achieves the non-Abelian braiding of up to five photonic modes. The braiding is realized by controlling the multi-mode geometric-phase matrix in judiciously designed photonic waveguide arrays. The quintessential effect of braiding--sequence-dependent swapping of photon dwell sites is observed in both classical-light and single-photon experiments. Our photonic chips are a versatile and expandable platform for studying non-Abelian physics, and we expect the results to motivate next-gen non-Abelian photonic devices.