Markovian-feedback-controlled entanglement and Einstein-Podolsky-Rosen steering in a nondegenerate optical parametric oscillator

We propose a scheme to manipulate entanglement and the direction of asymmetric Einstein-Podolsky-Rosen (EPR) steering between two interacting bosonic modes in a nonlinear optical apparatus, in which a pumped Fabry-Pérot cavity system containing two nonlinear waveguides is coupled to two feedback loops. It is found that Markovian feedback plays a key role in controlling both entanglement and EPR steering, the maximal entanglement can only be achieved through two symmetric feedback loops, while one-way EPR steering can only occur when both asymmetric feedback loops and an unbalanced beam-splitter are satisfied simultaneously. Furthermore, in terms of an unequal beam-splitter and two different feedback loops, it is demonstrated that the directionality and extent of the asymmetric EPR steering can be readily controlled under certain conditions. A simple and sufficient condition is also revealed for generating two-way EPR steering. Moreover, the entanglement and EPR steering can be effectively enhanced by performing Markovian feedback. In addition, By choosing appropriate feedback strengths, two cavity modes can be driven into a pure two-mode squeezed vacuum state rather than a mixed two-mode Gaussian entangled state or a pure entangled dark state. We hope the proposed scheme will enhance our understanding of the fundamental asymmetry of EPR steering, and it may have potential applications in quantum computation and quantum communication.