Single-photon interferometry with orbital angular momentum circumvents standard wave-particle duality

The wave-like behavior of single quantum particles is suppressed whenever we try to learn more about their complementary particle-like property. For twopath interferometers, e.g., the Mach-Zehnder interferometer (MZI), a relation describing such complementary behavior was derived and subsequently experimentally tested for massive particles as well as for photons. This relation sets an upper bound on possible joint observation of particle-like properties, quantified by the paths’ distinguishability, and wave-like properties, quantified by the visibility, which is very closely related to the sensitivity of the fringes to small phase changes. This duality relation reduces to a tradeoff between our which-way and which-phase knowledge, the latter being our ability to discern different phase shifts between the MZI arms. In this Letter, we propose a scheme that is predicted to yield, counterintuitively, considerably more accurate results for simultaneous path-distinguishability and phase-sensitivity of a photon emerging from a MZI than those predicted by the conventional complementarity relation.