Still More Squeezing of Optical Noise

Quantum optics experimenters have been pushing hard to generate greater “squeezing.” This drive was encouraged by last year's milestone demonstration at AT&T Bell Labs that the noise from an optical cavity had been measurably squeezed, that is, that the noise in one phase of the signal had been reduced below the level normally associated with quantum mechanical fluctuations in the vacuum field. Until then, that vacuum noise level had represented the fundamental quantum limit to precision in optical experiments. The Bell Labs experiment reduced the noise by 7–10% below this normal quantum limit (see PHYSICS TODAY, March 1986, page 17), and several experiments since then have achieved noise reductions of at least 20%. The most spectacular results to date have been obtained by a team at the University of Texas at Austin consisting of Ling‐An Wu, Min Xiao, H. Jeffrey Kimble, John L. Hall (of the Joint Institute for Laboratory Astrophysics) and Huifa Wu, who have observed noise reductions to more than 60% below the normal level.