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We investigate the enhancement of optomechanically induced entanglement in a single-cavity optomechanical system via three coherent feedback configurations (pump-only, probe-only, and dual feedback configurations). Without feedback, the pump-probe entanglement is weak and exists in a narrow range of detuning. The feedback enhances the entanglement and broadens the entangled range of detuning for the three configurations. The dual feedback shows stronger entanglement than the pump-only/probe-only feedback. With moderate feedback coefficient, the entanglement degree between two beams reaches ∼6dB, much higher than ∼0.3dB without feedback. The entanglement exists mainly in the positive feedback region. Furthermore, two criteria are used, Duan-Giedke-Cirac-Zoller (DGCZ) and logarithmic negativity (LN). The entanglement region with the LN criterion is broader than the DGCZ criterion, which is consistent with the previous theory.
Hu et al. (Fri,) studied this question.