This special issue is composed mainly of extended versions of talks and papers
presented at the Seventh International Conference on Squeezed
States and Uncertainty Relations held in Boston, Massachusetts, USA, on 4-8 June 2001.
The conference was hosted by Boston University.
The first meeting of this kind took place in College
Park, Maryland, USA in 1991 as a small workshop. The second and third meetings were
held in Moscow, Russia and Baltimore, USA in 1992 and 1993,
respectively. The fourth meeting took place in Taiyuan, Shanxi
Province, China in 1995 as an international conference sponsored by the
International Union of Pure and Applied Physics. The fifth
and sixth meetings were held in Balatonfüred, Hungary and
Naples, Italy in 1997 and 1999, respectively. The eighth
conference will take place in Puebla, Mexico in 2003.
The contributions to this special issue address, in the first instance, the foundations of quantum mechanics and quantum optics, and
several modern topics which have been intensively developed during
the last decade. Quantum fluctuations, squeezing phenomena and
different kinds of nonclassical states of light represent some of
the most intensively discussed subjects. In particular, several
papers deal with the properties of different kinds of `Schrödinger cat states' modelled in the simplest case by the
even and odd coherent states. This paradigm exhibits in
the most distinct form such cornerstone properties of quantum
mechanics as the superposition principle, which manifests itself
in quantum interference and entanglement.
The quantum entanglement phenomenon has been studied intensively
for the past few years due to its importance, for example, in
quantum computer projects. In spite of the fact that this concept was known
from the beginning of quantum mechanics, its properties, for example, the most appropriate entanglement measures, are still areas
of discussion. Another related aspect of quantum nature is
teleportation, which is also a subject of intensive study.
The phenomena of dissipations and decoherence of the initial pure
states are also very important, because fast decoherence can
destroy all the advantages of quantum processes in quantum
computing, teleportation and image processing. Due to these aspects, papers concerning various methods of controlling
the decoherence, for example, by means of using different kinds
of nonlinearities and deformations, are also presented here.
From the very beginning of quantum mechanics, the uncertainty
relations were basic inequalities distinguishing the classical and
quantum worlds. Developing a deeper understanding of the well-known
uncertainty relations and striving to find new ones (connected with purity
parameters of states, entropy, etc.) is an important aspect of modern research. Recently developed tomographic methods of
measuring quantum states (in terms of the Wigner function or other
phase-space characteristics) have resulted in the formulation of
quantum mechanics in which the standard probability density
describes the quantum states in an alternative way to the density matrix or
wave function. Some papers devoted to tomographic methods of measuring quantum states and studying
different sorts of uncertainty relations are presented here.
Group-theoretical methods of studying quantum-mechanical
and quantum-optical phenomena, including the group-representation
description of light polarization, also attract ongoing interest in the conference series discussions.
We hope that this special issue will help readers to
obtain an overview of the current trends in modern quantum optics,
both experimental and theoretical.
Young S KimUniversity of Maryland, College Park, USAMargarita A Man'koP.N. Lebedev Physical Institute, Moscow, RussiaAlexander Sergienko Boston University, MA, USA
Guest Editors