Unambiguous quantum measurement of nonorthogonal states

Generalized quantum measurements can be used to separate deterministically two nonorthogonal quantum states. However, such measurements also lead to inconclusive results, where the initial state remains unknown. We introduce a particular type of generalized quantum measurement, which we term loss induced generalized (LIGe) quantum measurement, and present an experimental realization. This LIGe measurement achieves optimal deterministic separation of two nonorthogonally polarized single photons. \textcopyright{} 1996 The American Physical Society.