Some studies in coherent states and squeezed coherent States.

Thomas Godsk Jørgensen

Koushik Mandal, Pooja Jethwani, Satyanarayana, M. Venkata

Coherent signal containing squeezed noise in a mixed state of radiation field is considered here as a non-Gaussian mixture of a coherent state density operator and a squeezed state density operator, as opposed to the usual well known squeezed coherent state. Both these states are `quantum' noise-included signal states. Effects of these two distinct ways of adding squeezing to a coherent state are compared and contrasted. The main objective of this work is to study the mixed state version of the Jaynes-Cummings model in the context of a two-level atom interacting with a mixed field state of a squeezed vacuum and a coherent state. The pure squeezed coherent state (PSCS) and the mixed squeezed coherent state (MSCS) are used as the states of the radiation field. The photon-counting distribution (PCD), the atomic inversion and the entanglement dynamics of atom-field interaction for both the radiation fields are investigated and compared with each other. We observe that depending on the state of the field, squeezing has very different effects on coherent photons. Mild squeezing on the coherent photons strongly localizes the PCD for PSCS; however, for MSCS there is no such localization observed - instead squeezing manifests for MSCS as oscillations in the PCD. The effects of squeezing on the atomic inversion and the entanglement dynamics for MSCS are contrasting in comparison with the corresponding quantities associated with PSCS. It is well known in the literature that for PSCS, increasing the squeezing increases the well-known ringing revivals in the atomic inversion, and also increases irregularity in the entanglement dynamics. However, increasing the squeezing in MSCS very significantly alters the collapse-revival pattern in the atomic inversion and the entanglement dynamics of the Jaynes-Cummings model.

M. Venkata Satyanarayana

Roy and Virendra Singh showed that the harmonic oscillator possesses an infinite string of exact shape-preserving coherent wave-packet states \ensuremath{\Vert}n,\ensuremath{\alpha}〉 having classical motion. In this paper it is shown that the states \ensuremath{\Vert}n,\ensuremath{\alpha}〉 could be obtained from the coherent state \ensuremath{\Vert}\ensuremath{\alpha}〉 and it is also shown how a coherent state \ensuremath{\Vert}\ensuremath{\alpha}〉 could be expanded in the basis of \ensuremath{\Vert}n,\ensuremath{\alpha}〉's. Further, the possibility of ``squeezing'' the state \ensuremath{\Vert}n〉 is investigated and the ``generalized squeezed coherent states'' are obtained. The squeezed coherent states for the displaced oscillator are also defined. The physical meaning of squeezing is also pointed out.

Willi-Hans Steeb

Anhua Zou

We mainly examine the nonclassical statistical properties of both squeezed even and Squeezed odd coherent states defined by the superposed states involving two squeezed coherent states with a phase difference n between their displacement parameters. We demonstrate that the fields in squeezed even coherent state can exhibit remarkably enhanced squeezing level and mean photon number in comparison with the input squeezed coherent state. We also point out the examples of the physical processes leading to such a superpotition.