Non-Hermitian Bulk-Boundary Correspondence in Quantum-Walk Dynamics

报告摘要：Bulk-boundary correspondence, a central principle in topological matter relating bulk topological invariants to edge states, fails in a general class of non-Hermitian systems. In this talk, we show that the breakdown of bulk-boundary correspondence also occurs for discrete-time quantum walks, a particular type of Floquet dynamics, when an appropriate form of non-unitarity is introduced. Based on the understanding of static non-Hermitian topological models, we define non-Bloch topological invariants for the quantum-walk dynamics, which give rise to the non-Hermitian bulk-boundary correspondence. We experimentally confirm our theoretical predictions by observing non-Hermitian skin effect and non-Hermitian bulk-boundary correspondence in discrete-time non-unitary quantum-walk dynamics of single photons. Our work unequivocally establishes the non-Hermitian bulk-boundary correspondence as a general principle underlying non-Hermitian topological systems, and paves the way for a complete understanding of topological matter in open systems.