title: Multimode quantum interference of photons in multiport integrated devices.
abstract: Photonics is a leading approach in realizing future quantum technologies and recently, optical waveguide circuits on silicon chips have demonstrated high levels of miniaturization and performance. Multimode interference (MMI) devices promise a straightforward implementation of compact and robust multiport circuits. Here, we show quantum interference in a 2 × 2 MMI coupler with visibility of V=95.6 ± 0.9%. We further demonstrate the operation of a 4 × 4 port MMI device with photon pairs, which exhibits complex quantum interference behaviour. We have developed a new technique to fully characterize such multiport devices, which removes the need for phase-sensitive measurements and may find applications for a wide range of photonic devices. Our results show that MMI devices can operate in the quantum regime with high fidelity and promise substantial simplification and concatenation of photonic quantum circuits.
authors.affiliation: Centre for Quantum Photonics, H. H. Wills Physics Laboratory & Department of Electrical and Electronic Engineering, University of Bristol, Merchant Venturers Building, Woodland Road, Bristol BS8 1UB, UK.
authors.forename: Alberto
authors.initials: A
authors.lastname: Peruzzo
authors.forename: Anthony
authors.initials: A
authors.lastname: Laing
authors.forename: Alberto
authors.initials: A
authors.lastname: Politi
authors.forename: Terry
authors.initials: T
authors.lastname: Rudolph
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: O'Brien