In this tutorial article the authors provide a discussion of squeezed states of light from an elementary point of view. An outline of the topics considered is provided in the contents list below. Following the presentation of topics 1-3, which are of a general nature, they discuss two kinds of nonclassical light: quadrature-squeezed light (topics 4-6) and photon-number-squeezed light (topics 7-9). In the last part of the article they provide a listing of early nonclassical light experiments and consider a number of applications (and potential applications) of squeezed light. Finally, they provide a survey of the available general literature.
In this tutorial article the authors provide a discussion of squeezed states of light from an elementary point of view. An outline of the topics considered is provided in the contents list below. Following the presentation of topics 1-3, which are of a general nature, they discuss two kinds of nonclassical light: quadrature-squeezed light (topics 4-6) and photon-number-squeezed light (topics 7-9). In the last part of the article they provide a listing of early nonclassical light experiments and consider a number of applications (and potential applications) of squeezed light. Finally, they provide a survey of the available general literature.
This chapter reviews theoretical and experimental aspects of non-classical states of light, e.g., squeezed states and number states. The definition of squeezed states and a review of their general properties is followed by a discussion of special kinds of squeezing, e.g., squeezed coherent states, displaced squeezed states, and amplitude or phase squeezing. An overview of photon counting statistics and robustness of squeezed states is followed by a theoretical model of their generation and a description of their experimental production. The chapter ends with a brief discussion of the experimental generation of number states, including methods for generation of single-photon states on demand, which have applications to quantum information processing.
The generation of nonclassical light has recently received a great deal of attention because three forms of it have now been observed in the laboratory: antibunched light, photon-number-squeezed (or sub-Poisson) light, and quadrature-squeezed light. These characteristics may, but need not, accompany each other in any given light source. Nonclassical light has been produced in experiments using resonance fluorescence, the Franck-Hertz effect, parametric interact ions, and semiconductor light sources. It is likely to be useful in providing new insights in various physical and biological processes, and in applications such as lightwave communications. Some of the characteristics, methods of generation, and expected uses of squeezed light will be addressed.
This Resource Letter provides a brief introduction and an annotated guide to the literature about the roles of quantum coherence in quantum optics. Books, conference proceedings, and selected journal articles are listed for the following topics: Early history, lasers, in particular novel systems such as lasers without inversion, nonclassical states of light including squeezed states, cavity quantum electrodynamics, cooling and trapping of atomic samples, atom optics, and quantum optical tests of the foundations of quantum mechanics.
Electromagnetic fields, with the noise on one quadrature component reduced to below the quantum mechanical zero-point fluctuation level and the noise on the other quadrature component enhanced to above it, are currently of great interest in quantum optics because of their potential applications to various precision measurements. Such squeezed states of light are usually produced by imposing nonlinear unitary evolution on coherent (or vacuum) states. On the other hand, squeezed states with reduced photon number noise and enhanced phase noise are generated directly by a constant current-driven semiconductor laser. This is the simplest scheme for the generation of nonclassical light, and so far it has yielded the largest quantum noise reduction. The mutual coupling between a lasing junction and an external electrical circuit provides opportunities for exploring the macroscopic and microscopic quantum effects in open systems.
Seventy five years ago, three remarkable papers by Schrödinger, Kennard and Darwin were published. They were devoted to the evolution of Gaussian wave packets for an oscillator, a free particle and a particle moving in uniform constant electric and magnetic fields. From the contemporary point of view, these packets can be considered as prototypes of the coherent and squeezed states, which are, in a sense, the cornerstones of modern quantum optics. Moreover, these states are frequently used in many other areas, from solid state physics to cosmology. This paper gives a review of studies performed in the field of so-called `nonclassical states' (squeezed states are their simplest representatives) over the past seventy five years, both in quantum optics and in other branches of quantum physics. My starting point is to elucidate who introduced different concepts, notions and terms, when, and what were the initial motivations of the authors. Many new references have been found which enlarge the `standard citation package' used by some authors, recovering many undeservedly forgotten (or unnoticed) papers and names. Since it is practically impossible to cite several thousand publications, I have tried to include mainly references to papers introducing new types of quantum states and studying their properties, omitting many publications devoted to applications and to the methods of generation and experimental schemes, which can be found in other well known reviews. I also mainly concentrate on the initial period, which terminated approximately at the border between the end of the 1980s and the beginning of the 1990s, when several fundamental experiments on the generation of squeezed states were performed and the first conferences devoted to squeezed and `nonclassical' states commenced. The 1990s are described in a more `squeezed' manner: I have confined myself to references to papers where some new concepts have been introduced, and to the most recent reviews or papers with extensive bibliographical lists.