Quantum Fluctuations

by Peter W. Milonni (Author)
This is an introduction to the quantum theory of light and its broad implications and applications. A significant part of the book covers material with direct relevance to current basic and applied research, such as quantum fluctuations and their role in laser physics and the theory of forces between macroscopic bodies (Casimir effects)

The concept of squeezing is intimately related to the idea of vacuum fluctu­ ations, once thought to place an absolute limit to the accuracy of measure­ ment. However, vacuum fluctuations are not unchangeable. By recognizing that these quantum fluctuations always occur in two complementary observ­ ables, physicists have been able to make an intriguing trade-off. Reduced fluctuations in one variable can be realized - at the expense of increased fluctuations in another, according to Heisenberg. This Heisenberg 'horse-trade' - originally predicted by theorists - was first accomplished experimentally by R. Slusher in 1985. Since then, the var­ ious techniques and applications of quantum squeezing have metamorphosed into a central tool in the wider field of quantum information. This book is a summary of the main ideas, methods and applications of quantum squeezing, written by those responsible for some of the chief developments in the field. The book is divided into three parts, to recognize that there are three areas in this research. These are the fundamental physics of quantum fluc­ tuations, the techniques of generating squeezed radiation, and the potential applications. Part I of the book, giving the fundamentals, is arranged as follows. • Chapter 1 introduces the basic ideas about what squeezing of quantum fluctuations is from the quantized free-field perspective. This chapter es­ tablishes the definitions and notations used throughout. • Chapter 2 explains how to quantize radiation in a dielectric, which is the basic technique that is used to make squeezed radiation.

As a graduate student working in quantum optics I encountered the question that might be taken as the theme of this book. The question definitely arose at that time though it was not yet very clearly defined; there was simply some deep irritation caused by the work I was doing, something quite fundamental I did not understand. Of course, so many things are not understood when one is a graduate student. However, my nagging question was not a technical issue, not merely a mathematical concept that was difficult to grasp.

This book presents a complete encyclopedia of superconducting fluctuations, summarising the last thirty-five years of work in the field.