Proposal for measuring topological invariants in photonic system in Physical Review Letters

Recently, quantum Hall Hamiltonians have been implemented in photonic systems and their corresponding topological edge states have been observed. In electronic systems, it is known that the existence of topological order leads to "quantized conductance''. However, what is not clear is that how the integer values of such topological invariants manifest themselves in an optical realization. In this letter, we propose a scheme to measure the integer topological invariants of a photonic system and elucidate the connection between the quantized conductance in electronic systems and topological invariants in photonic systems.