Coherent state expansion of squeezed states

Петер Адам, József Janszky, Aleksandr V Vinogradov

Xiang-You Chen, Yuyu Zhang, Libin Fu +1 more

We develop a coherent-squeezed-state expansion for the ground state of the quantum phase transition in the quantum Rabi model. The wave function undergoes a transition from a localized state in the normal phase to a two-peaks delocalized state in the super-radiant phase. Interestingly, the two displaced wave packets are squeezed in the momentum space, and overlap strongly to form a correlated state. We develop a superposition of coherent-squeezed states to describe the phase transition correctly, which includes the higher-order excitations at the critical value. The corresponding ground-state energy and the average photon number are in agreement with numerical ones, exhibiting an improvement over previous coherent-state expansions. Moreover, our method successfully captures the reduced quantum fluctuations in momentum variable in the phase transition.

Chon‐Fai Kam, Wei-Min Zhang, D.H. Feng

Pradip Das

Jiaxin Gong, P. K. Aravind

An analytic expression is obtained for the expansion coefficients of a single-mode squeezed coherent state in the number state (or Fock) basis. This is done by deriving a set of coupled recursion relations for the coefficients that are solved in closed form. The result coincides with that of Stoler and Yuen but the present method has the advantage (for neophytes) that it does not involve any sophisticated operator ordering techniques. Thus the present approach is suitable for inclusion in a course on quantum mechanics dealing with squeezed states.

A. D. Jannussis, Vasileios Bartzis, E. Vlahos