Coherent and squeezed states on physical basis

Vladimir P Bykov

The physical picture of the properties of light in squeezed and in other nonclassical states is presented and compared with the properties of light in the classical coherent state. The theoretical basis of the description and the generation of squeezed light is presented, and a practical scheme for obtaining light in other of its nonclassical states is discussed. The general nature of the phenomenon is emphasized, as well as the possibility of its transfer to other fields such as acoustics, mechanics, and various Bose fields.

Willi-Hans Steeb

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.

Amir Karimi, Mohammad Kazem Tavassoly

Tamíris R. Calixto, Pablo L. Saldanha

Coherent states are normally used to describe the state of a laser field in experiments that generate and detect squeezed states of light. Nevertheless, since the laser field absolute phase is unknown, its quantum state can be described by a statistical mixture of coherent states with random phases, which is equivalent to a statistical mixture of Fock states. Here we describe single-mode squeezed vacuum experiments using this mixed quantum state for the laser field. Representing the laser state in the Fock basis, we predict the usual experimental results without using the squeezing concept in the analysis and concluding that no squeezed state is generated in the experiments. We provide a general physical explanation for the noise reduction in the experiments in terms of a better definition of the relative phase between the signal and local oscillator fields. This explanation is valid in any description of the laser field (in terms of coherent or Fock states), thus providing a deeper understanding of the phenomenon.