Invisible non-Hermitian potentials in discrete-time photonic quantum walks

Discrete-time photonic quantum walks on a synthetic lattice, where both spatial and temporal evolution of light are discretized, have recently provided fascinating platform for the observation wealth non-Hermitian physical phenomena control scattering in complex media. A rather open question is whether invisible potentials, analogous to ones known continuous optical media, do exist such discretized systems. Here it shown that, under certain conditions, slowly drifting Kramers–Kronig potentials behave as discrete-time walks.