Single-particle interference versus two-particle collisions

We consider a mesoscopic circuit in the quantum Hall effect regime comprising two synchronized single-particle sources emitting particles into a Mach-Zehnder interferometer. While particles from one source can possibly interfere at the interferometer output, particles from the second source are injected directly into one of the interferometer's arms and are used to create tunable and coherent suppression of interference. If particles from the two different sources collide at the interferometer output the magnetic-flux dependence of the charge transferred to one of the output contacts is suppressed. In contrast the interference pattern in the current at a fixed time is preserved and the impact of the second source manifests itself in a time-dependent phase-shift.