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Journal of Modern Optics

Representations of Squeezed States with Thermal Noise

H. Fearn, Matthew J. Collett

Published Mar 1, 1988• 107 citations
Publisher

Abstract

Some of the possible representations of squeezed states with thermal noise are discussed and their various physical interpretations elucidated. Both thermofield techniques and a density operator description are employed, and their results related to one another where possible.
DOI
10.1080/09500348814550571

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The thermofield introduced by Takahashi and Umezawa [Collect. Phenom. 2, 55 (1975)] is used to represent the thermal noise; it is generated from the absolute vacuum by a so-called thermalizing operator and serves as the initial state for generating two-mode squeezed states by squeeze and displacement operators. The ones obtained by applying the squeeze operator first followed by the displacement operator are called coherent squeezed states, while the others obtained by applying the displacement operator first are called squeezed coherent states. A criterion for the existence of nonclassical photon statistics in a two-mode radiation introduced by us in a previous paper [Phys. Rev. A 42, 1609 (1990)] is then used to study the conditions for the two types of squeezed states to be nonclassical states. Several three-dimensional plots are presented to illustrate the effects of thermal noise on squeezed states.