Non-Abelian Thouless pumping in photonic waveguides

Non-Abelian Thouless pumping, whose outcome depends on the order of pumping operations, has been observed in photonic waveguides with degenerate flat bands. Thouless pumping enables topological transport and the direct measurement of topological invariants. So far, realizations of Thouless pumping rely on the adiabatic evolution of a physical system following a non-degenerate band, but it has been predicted that pumping can become non-Abelian in nature when degenerate bands exist. The resulting non-Abelian gauge fields and associated non-commutative operations would be promising for applications related to unitary matrices, such as photonic quantum logic. Here we propose the experimental realization of non-Abelian Thouless pumping in an on-chip photonic platform. By modulating the coupling coefficients within photonic waveguides with degenerate flat bands, we observe non-Abelian Thouless pumping in a three-step pumping device where the outcomes depend on the sequence of the pumping operations. We anticipate our versatile platform to reveal more complex non-Abelian topological physics and realize on-chip non-Abelian photonic devices in the future.

Automated summary

Non-Abelian Thouless pumping has been experimentally realized in an on-chip photonic platform, where the outcome depends on the sequence of pumping operations. This study can reveal more complex non-Abelian topological physics and has the potential to realize on-chip non-Abelian photonic devices.