Dipole squeezing in the Jaynes-Cummings model with and without the rotating wave approximation (RWA) has been numerically studied when restricted to the following initial conditions: the field in the superposition of the vacuum and one-photon state, and the atom in the ground state. Numerical results show that even if under the condition for which the RWA is considered to be valid, there is a significant effect caused by the virtual-photon field on the dipole squeezing; in the cases of sufficiently strong coupling of the atom-field interaction, the interference between the virtual-photon processes and the real-photon processes quenches the dipole squeezing.
We have studied the influence of thermal photons on the symmetry between the field and atomic squeezing (SFAS) exposed in the resonant vacuum-field Jaynes-Cummings model with an initially coherent atom. We have shown that when the number of thermal photons ( N av ) is less than 0.01, the SFAS is not sensitive to the presence of thermal photons; when N av ⩾ 0.01, the broken SFAS can be seen; when N av ⩾ 0.1, the squeezed atom cannot radiate a squeezed field any longer. Also, we have discussed the possibility of detection of the boken symmetry in superconducting maser cavity.
We use the recently-established asymptotic solution (AS) for large fields to study squeezing in the Jaynes-Cummings model. Arbitrary initial atomic states (including atomic coherence) are considered. We find that most features of squeezing can be understood from the properties of the asymptotic field states, and from the observation, which we establish numerically, that for large fields the interference between the two branches of the wavefunction does not contribute significantly to the squeezing (not even near the revival times, when the two field states being superposed have very nearly the same phase). We obtain a limit on the time over which the field may show any squeezing and find that it scales as the 3/4 power of the number of photons. We also obtain a bound on the maximum achievable squeezing for a given number of photons, which is an improvement over earlier estimates. Finally, we discuss some of the shortcomings of the AS, and in particular the existence of a small ghost peak in the field Q function for initial conditions where the AS predicts a single peak, which is enough to destroy the squeezing for certain times.
We study interaction between a pair of indistinguishable two-level atoms and the single-mode cavity field. It is supposed that the pair of two-level atoms is laser cooled and trapped into the ground vibrational state, in which vibrational quantum number
⟨nv⟩=0 . Two Jaynes–Cummings models are investigated. One is the Jaynes–Cummings model with intensity-dependent coupling and the another is the two-photon Jaynes–Cummings model of a pair of indistinguishable two-level atoms. It should be noted that in the present model, at initial moment
t=0 , in intensity-dependent Jaynes–Cummings model the cavity field is prepared in Holstein–Primakoff SU(1,1) CS, while in two-photon Jaynes–Cummings model it is prepared in the squeezed vacuum state. Moreover, at initial moment
t=0 , pair of atoms is supposed to be in the first excited state
∣e1⟩ in both models. By using exact analytical solutions for state-vectors of the coupled atom-field systems amplitude-squared squeezing of the quantized cavity field is examined as a function of the
∣ξ∣ parameter. In this situation, in both models higher-order squeezing has the tendency towards oscillations, but exact periodicity of these oscillations is violated by the analogy with the second-order squeezing.