Ken Mochizuki

TL;DR: In this article, spontaneous parity and topological edge states are observed in a photonic non-Hermitian system with a quantum walk interferometer, where topological parity is achieved by time symmetry breaking.

TL;DR: In this article, the authors study the symmetry of the time-evolution operator of nonunitary quantum walks and provide a necessary and sufficient condition that the non-unitary walk retains symmetry even when parameters of the model depend on position.

TL;DR: In this article, a procedure to calculate topological numbers from non-unitary time-evolution operators with chiral symmetry is presented, and the topological number obtained from the derived procedure gives correct predictions of the emergent edge states.

TL;DR: The eigenvalue statistics of a non-Hermitian version of the Su-Schrieffer-Heeger model, with imaginary on-site potentials and randomly distributed hopping terms, find that eigenvalues can be purely real in a certain range of parameters, even in the absence of parity and time-reversal symmetry.

TL;DR: In this article, the stability of topologically protected edge states has been studied for a quantum walk with nonlinear effects, which is akin to time-periodically driven systems (Floquet systems), and the authors find additional bifurcations at which edge states change from stable attractors to unstable repellers with increasing the strength of nonlinearity in nonlinear quantum walks.