Abstract

A hallmark of topological band theory in periodic media is that bulk properties are not affected by boundary conditions. Remarkably, in certain non-Hermitian lattices, the bulk properties are affected largely by boundaries, leading to such major effects as the non-Hermitian skin effect and violation of the bulk-boundary correspondence. Here, we unveil that non-unitary discrete-time quantum walks of photons in systems involving gain and loss show rather generally non-Bloch parity-time symmetry-breaking phase transitions and suggest a bulk probing method to detect such boundary-driven phase transitions.

© 2019 Optical Society of America

Quantum statistical signature of $ {\cal P}{\cal T} $PT symmetry breaking

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Transmission through a one-dimensional photonic lattice modulated by the side-coupled PT-symmetric non-Hermitian Su–Schrieffer–Heeger chain

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