Seminarium KMMF "Teoria Dwoistości"

We present an inequality relating visibility and which-wayinformation for a particle equipped with an internal degree of freedomtravelling through a Mach-Zehnder interferometer. The inequality paintsan unexpectedly intricate picture of wave-particle duality in thegeneral case. Strikingly, in some instances which-way informationbecomes erased by introducing classical uncertainty in the internaldegree of freedom. Furthermore, even imperfect interference visibilitymeasured for a suitable set of inputs can be sufficient to infer absenceof which-way information.