Coherent Nonlinear Quantum Feedback with Applications to On-Chip Quantum Optics

Abstract

AbstractIn the control of classical mechanical systems, the feedback has been successfully applied to the production of desired nonlinear dynamics. However, how much this can be done is still an open problem in quantum mechanical systems. This paper proposes a novel scheme of generating strong nonlinear quantum effects via the recently developed coherent feedback technique, which outperforms the measurement-based quantum feedback scheme that can only generate pseudo-nonlinear quantum effects. Such advantage is demonstrated by two application examples in quantum optics on chip. In the first example, we show that in a transmission line resonator (TLR), the nonlinear Kerr effect can be generated and amplified to be comparable with the linear effect. In the second example, we show that by tuning gains of quantum amplifiers in a TLR coherent feedback network, non-Gaussian light can be generated and manipulated via the nonlinear effects featured by fully quantum sub-Poisson photoncount statistics and photon antibunching phenomenon. The scheme opens up promising applications in demonstrating strong nonlinear quantum optics on chip, which is extremely weak and inflexible in traditional quantum optical devices.