Quantum-state engineering using nonlinear optical Sagnac loops

Abstract

The Kerr nonlinearity of an optical-fibre Sagnac loop can be utilized to engineer a variety of two-photon quantum states. These include correlated, identical photon pairs as well as degenerate, maximally entangled states - both of which are used in quantum information processing. In fact, their underlying principle - the reverse Hong-Ou-Mandel effect - can also be applied to free-space, down-conversion-based analogues of either identical or entangled photon-pair sources. Due to their simple structure, such versatile devices are expected to find widespread applications in quantum-state engineering. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.