Can Phonons Squeeze their Way Into the Company of Photons?

JUN 01, 1997

The noise can be squeezed out of a light signal until it falls considerably below the quantum, or shot, limit. Now researchers are trying to use a similar trick to reduce the noise associated with phonons.

DOI: 10.1063/1.881762

Barbara Goss Levi

Twelve years ago, Richart Slusher and his colleagues at AT&T Bell Labs produced light whose noise was below the vacuum quantum fluctuations, at least in part of the signal. Since then, researchers have been trying to squeeze the uncertainties out of other systems as well. So far they have succeeded in quieting a classical mechanical oscillator and both classical and nonclassical states of a vibrating, trapped ion. Now comes a report of squeezed phonons: By striking a crystal with a femtosecond laser pulse, a group at the University of Michigan believes it has excited an acoustic mode whose variance falls below the standard quantum limit. So far, the noise has been reduced by only 0.01% (the earliest experiments on optical squeezing yielded 20%), but just the concept of squeezed phonons has intrigued many observers.