Listening with a ‘quantum ear’

Published in Physics World, 9 Feb 2012

Physicists are very good at making measurements with single photons of light. Soon, however, they may also be doing routine studies of single phonons – single quanta of sound. That is the claim of physicists in Sweden and Germany, who say they have detected acoustic waves that are so weak they are – almost – at the quantum limit.

Recent years have seen a great effort to work with mechanical oscillations in the quantum regime. In such a regime, a mechanical device would be able to both emit and detect single phonons – just as optoelectronic devices are already able to emit and detect single photons. In 2010 a group at the University of California, Santa Barbara, US, demonstrated that it could create single phonons using a cryogenically cooled mechanical oscillator, thereby taking the first step on the quantum road. […]

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