Effect of an auxiliary mode on bipartite entanglement in a dissipative three-mode optomechanical system

The influence of a fast damped auxiliary mode on the creation of bipartite entanglement in a dissipative three-mode optomechanical system is investigated. We show how the reduction of fluctuations of the modes and the creation of the entanglement depend on the type of the coupling between the auxiliary and the other modes. A detailed calculation of the inseparability parameter is presented for three different types of couplings possible in the system: (a) nonlinear parametric-type, (b) linear-type, and (c) linear-type coupling to one of the two modes and parametric-type coupling to the other mode. Our calculations reveal the necessity of having a parametric-type coupling in the system. We find, however, that the presence of the linear-type rather than the parametric-type coupling protects the modes from excess noise. In particular, we show that in (a)–(c) cases a strong linear-type coupling between some of the mode leads to a significant reduction of the fluctuations of the modes, and in the (b) and (c) cases the presence of a strong linear-type coupling between the auxiliary and the other modes results in an entanglement between the modes. Graphical abstract