Implementation of nonlocal multiphoton interference by mode swapping

Multiphoton interference can be observed using independently generated photons as input. In the most simple case, these photons meet up at a beam splitter, resulting in quantum interference between transmission and reflection of the photons. Here, we show that non-local multiphoton interference can be implemented by using a mode swap operation to generate entanglement between the photons detected in the outputs of two spatially separated interferometers. The spatial separation of the output photons makes this implementation of multiphoton interference particularly suitable for quantum protocols that distribute quantum information to different parties.