Article
Zeno and Anti Zeno effect for a two level system in a squeezed bath
Physical Review A (Impact Factor: 3.04). 10/2005; DOI:10.1103/PhysRevA.73.042113
Source: arXiv
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Article: Quantum Measurement
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ABSTRACT: In recent years advances in technology, especially in the field of quantum optics, have made possible repetitive quantum measurements on a single quantum object, an issue that remained an academic curiosity until 25 years ago. This book, first published in 1992, provides a tutorial introduction to this field. The book is coauthored by an experimentalist and a theorist: the former  Braginsky  was the first experimentalist after Weber to develop techniques for gravitationalwave detection; the latter  Khalili  contributed with Braginsky to develop the formal apparatus to describe the experimental devices for measurement schemes. After the first part, intended as a pedagogical appendix of a standard textbook, and devoted to the modern approach to quantum measurement, the second part is a review of some new methods of quantum measurements for macroscopic objects. The central problem is the detection of a small timedependent classical force that acts on a quantum probe. This is the typical situation that occurs in gravitationalwave detection, where the probe is a macroscopic moving mass weakly coupled to a classical wave. The problem of gravitationalwave detection and the limitation to accuracy of measurement of position of a moving mass  the socalled standard quantum limit (SQL), which is a consequence of the random backaction of the measuring device on the mass  triggered the development of new quantum nondemolition (QND) measurements, i.e. measurements where the measured quantity is left unperturbed after the measurement. SQL and QND measurements (both Braginsky inventions) permeate the whole book as a transversal chapter. The aim is to give simple criteria and recipes to design a measuring device in order to optimize the accuracy of the measurement, and, at the same time, to minimize the perturbation that the device exerts on the measured object, so that it will not interfere with successive measurements on the same object. The continuous measurements are regarded as the limiting case of a sequence of repeated discrete measurements, when the interval between the measurements is much smaller than the characteristic timescale on which the measured quantity changes. The analysis of continuous measurements give to the authors the opportunity to illustrate the watchdog effect and the quantum Zeno paradox (real effect), while deriving the master equation for the evolution of the object state. Then, an entire chapter is devoted to the analysis of devices for continuous measurement of small mechanical displacements. The book is easy to understand, and can serve as a complementary reading for graduate level courses in quantum mechanics. The material of the book can be useful for all scientists and engineers involved in researches related to highsensitive quantum measurements, quantum information theory and quantum computation. The reader, however, should be aware that this book presents a very particular point of view, with no room left to very relevant concepts in quantum measurement theory, as, for example, squeezing, quantum amplification, jointmeasurements of noncommuting observables and phasemeasurements. More regrettably, the list of references is unsatisfactorily incomplete, with no mention of alternative developments, for example, regarding the SQL for measuring the position of a free mass. Here, schemes to breach the SQL have been proposed in the literature (Yuen H P 1983 Phys. Rev. Lett. 51 719, Ozawa M 1988 Phys. Rev. Lett. 60 385), whereas from the book one could conclude that such SQL would be unsurpassable. Also, a criticism is in order of the way of deriving some SQL's, based solely on the Heisenberg relation, even in consideration that the aim of such derivations is mostly pedagogical.Measurement Science and Technology 07/2009; 8(7). · 1.44 Impact Factor 
Article: On Quantum Optics
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ABSTRACT: this paper is to show that in general for thermal radiation the correlation function does not decay completely to zero, but to a nonzero dindependent background value. This longrange correlation is smaller than the shortrange correlation by a factor (#/a) , and becomes dominant for d # r (#/a) 1/3 . It contains information on deviations of the thermal radiation from the blackbody limit10/2003;
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