Physics: Light squeezing

Bryan J. Dalton, Z. Ficek, S. Swain

Squeezed light is of interest as an example of a non-classical state of the electromagnetic field and because of its applications both in technology and in fundamental quantum physics. This review concentrates on one aspect of squeezed light, namely its application in atomic spectroscopy. The general properties, detection and application of squeezed light are first reviewed. The basic features of the main theoretical methods (master equations, quantum Langevin equations, coupled systems) used to treat squeezed light spectroscopy are then outlined. The physics of squeezed light interactions with atomic systems is dealt with first for the simpler case of two-level atoms and then for the more complex situation of multi-level atoms and multi-atom systems. Finally the specific applications of squeezed light spectroscopy are reviewed.

K. N. Alekseev

Roman Schnabel

Abstract The detectors of the international gravitational‐wave (GW) observatory network are currently taking data with sensitivities improved via squeezing the photon counting noise of the laser light used. Several GW candidate events, such as black‐hole mergers, are already in the pipeline to be analyzed in detail. While the brand‐new field of GW astronomy relies on squeezed light for reaching higher sensitivities, the physical understanding of such light, although being well described by quantum theory, is still under discussion. Herein, a physical description of why squeezed light, as now being exploited by GW observatories, constitutes rather remarkable physics is presented. Consideration of the Fourier transform seems to provide an argument why the measurement of squeezed photon statistics from quasi‐monochromatic light is “weird.” It is further argued that the measurement of squeezed photon statistics is related to the famous gedanken experiment formulated by Einstein, Podolsky, and Rosen in 1935. This work illuminates “quantum weirdness” in a clear way and might be the starting point for finding the physics of quantum correlations in general, which scientists have been seeking for decades.

P. Tzallas

Richart E. Slusher, Bernard Yurke

Matthew E. Anderson, Michael G. Raymer

Years after its first observation, squeezed light is still the premiere vehicle for demonstrating the importance of quantum mechanics in optics; it is an inherently "non-classical" signal field which eludes explanation by classical physics. Current progress in squeezing is being fueled by advances in nonlinear devices and measurement theory. Here we will briefly review the history of squeezed light and discuss the advantages of generating squeezed light in waveguides.