Abstract

Photons are unsurpassed as qubits in terms of decoherence times, mobility, and achievability of high-fidelity single-qubit operations. Thus far, entanglement experiments in optics have been very clean, and an optical quantum processor would obviously have an advantage in connecting to a quantum "network" (no need to convert between stationary and flying qubits). Nowadays, the limits of the original KLM [1] linear optics quantum computing proposal, as well as the more recent cluster and graph-state approaches [2], in addition to various nonlinear optical approaches are explored, but several challenges must be overcome: the logic devices are often probabilistic, large numbers of ancillae photons must be generated in entangled states, and high-efficiency detectors are required. Other research programs are developing single-photon sources and detectors. The most important issue is the practical scalability of quantum circuits, the ability to perform quantum logic gates with error rates below the fault-tolerant threshold and incorporate them into large-scale quantum circuits with realistic physical resources and single-photon detectors packed on an optical chip. Optical integrated circuits offer great potential for realizing previously unfeasible large-scale quantum circuits. The monolithic nature of these devices means both miniaturization of the circuits and also that the correct phase can be stably realized in what would otherwise be an unstable interferometer. Recently, different groups [3-4] demonstrated integrated circuits based on silica-on-silicon waveguides to implement quantum-information components. This flexible architecture can be used to implement key quantum-computation elements, including CNOT gates based on integrated directional couplers and reconfigurable single-qubit operations using phase controllers based on the thermo-optical effect of silica. We propose a novel architecture to implement a scalable quantum processor based on silicon-photonics overcoming the overhead due to multiple single photon sources and detectors.

© 2015 IEEE