Incoherent Non-Hermitian Skin Effect in Photonic Quantum Walks

The non-Hermitian skin effect describes the concentration of an extensivenumber of eigenstates near the boundaries of certain dissipative systems. Thisphenomenon has raised a huge interest in different areas of physics, includingphotonics, deeply expanding our understanding of non-Hermitian systems andopening up new avenues in both fundamental and applied aspects of topologicalphenomena. The skin effect has been associated to a nontrivial point-gapspectral topology and has been experimentally demonstrated in a variety ofsynthetic matter systems, including photonic lattices. In most of physicalmodels exhibiting the non-Hermitian skin effect full or partial wave coherenceis generally assumed. Here we push the concept of skin effect into the fullyincoherent regime and show that rather generally (but not universally) thenon-Hermitian skin effect persists under dephasing dynamics. The results areillustrated by considering incoherent light dynamics in non-Hermitian photonicquantum walks.