Abstract

Quantum-entangled photon pair sources are one of the key building blocks for applications in quantum metrology [1], quantum information processing and computing [2], and quantum key distribution (QKD) [3]. The generation of entangled photon pairs in various forms (i.e. polarization entanglement, energy-time entanglement and time-bin entanglement) has been demonstrated through spontaneous parametric down-conversion (SPDC) in diverse second-order nonlinear media (e.g. bulk nonlinear crystals) [4]. To deliver the compactness, scalability and efficiency required by future optical quantum circuit devices, solutions focusing on an integrated (on-chip) approach have been recently studied and developed exploiting spontaneous four wave-mixing (SFWM) [5]. Integrated micro-ring resonators with narrow resonances and high Q-factors, are of special interest since, in contrast to waveguide structures, they offer an enhancement in photon pair generation efficiency as well as a narrow photon pair bandwidth, rendering them compatible with quantum optical devices (e.g. high time resolution single photon detectors and quantum memories). More importantly, resonant nonlinear cavities such as ring resonators offer the possibility of generating photon pairs on multiple signal/idler frequency channels [6] due to the periodic and equidistant resonance structure, especially useful for exploiting multiplexed communication. However, up to now the generation of entangled photon pairs, a property that is required for quantum key distribution, has not been demonstrated for more than one signal-idler frequency pair.

© 2015 IEEE