Light Entanglement And Spin Squeezing In Detuned Quantum Beats

Quantum beat system is widely used in quantum optics, such as quantum beat laser, spontaneous emission cancellation and so on. The essence of quantum beats is atomic coherence. Due to the spontaneous emission, the coherence between the two excited states is rather vulnerable. Thus there is no long-lived coherence in quantum beat system. As a result, it is more difficult for us to obtain light entanglement and spin squeezing in quantum beat system. At present, quantum beats are little applied in obtaining light entanglement and spin squeezing. Owing to the importance of quantum beats in quantum optics, it is necessary for us to obtain light entanglement and spin squeezing in quantum beat system.Our work is to obtain light entanglement and spin squeezing in detuned quan-tum beats. We study an ensemble of V-type quantum beat atoms, which is coupled by two cavity fields. And symmetrical detuning is choosen to induce nonlineari-ties. Then we use dressed state presentation to describe the whole system. And the Bogoliubov modes of the fields and atom spins are introduced to our system. We can obtain two-mode squeezing and entanglement of the fields and atom spins by the dissipation effect of Bogoliubov modes. Based on the dissipation effect of the Bogoliubov modes, we have a qualitative analysis:the light entanglement and spin squeezing can be obtained when the parameter △/Ω are confined within the ranges of (-1,0), (0,(?)2/3), (1,+∞). At last we get the numerical results, which fit well with our qualitative analysis, explaining Bogoliubov modes dissipation is a direct mechanism to generate the squeezing and entanglement. According to the numerical results, we also find when the parameter is about△/Ω ≈(?)2/3, almost ideal two-mode squeezing and entanglement are achievable for the fields and atom spins under respective adiabatic conditions. Meanwhile, we also obtain the excited-state spin squeezing. Although the fluctuation is severely amplified by the spontaneous emission from the two excited states in quantum beats, the best spin squeezing of excited-state approaches 40%.