Tripartite entanglement via coherently enhanced six-wave mixing

In this paper, we show that the tripartite continuous-variable entanglement can be obtained by using coherently enhanced six-wave mixing process in a triple ΛΛ atomic system. Multiphoton resonances condition must be satisfied for the scheme. Due to atomic coherence, two of the cavity modes are pulled into a quantum beat and in the mixing interaction with the third cavity mode. This yields entanglement between the quantum-beat components and the third cavity mode. The pair of the beat modes is not entangled with each other, but they are both entangled with the third cavity mode. The generated tripartite entanglement is significantly dependent on the normalized detunings of the external coherent fields and the cooperativity parameters.