Institut d’Optique, Palaiseau, France

A physicist hopes that cool techniques could show up quantum effects in ‘big’ systems.

When I was a postdoc in Bell Labs during the 1980s, many of the ideas stimulating our work in quantum optics came from researchers developing sensors for gravitational waves.

Gravitational waves propagate as distortions in space, and a passing wave is expected to have a subtle influence on the oscillation of a heavy bar, or to change by a fraction the separation of two mirrors.

To minimize the uncertainty in measurements of such effects, researchers developed new concepts for manipulating the quantum fluctuations that affect parameters such as an oscillator’s position.

Concepts they invented, such as ‘quantum non-demolition measurements’ and ‘squeezed states’, have since been demonstrated (sometimes with my help), but with light beams rather than massive objects.

Detecting quantum effects in ‘big’ systems has remained an elusive goal, despite experiments moving to smaller masses and higher oscillation frequencies to make the quantum noise larger. The stumbling block has been heat — thermal excitations overwhelm the well-hidden quantum noise.

Here, recent work suggests a way forward. Three papers published last autumn (S. Gigan et al. Nature 444, 67–70; O. Arcizet et al. Nature 444, 71–74; D. Kleckner & D. Bouwmeester Nature 444, 75–78; 2006) each show that the techniques used to measure a micromirror’s motion can cool the mirror at the same time, pushing its temperature close to absolute zero.

Such cold micromirrors could well become the first ‘heavy-weight’ quantum-mechanical objects — and the techniques developed in quantum optics may eventually feed back into the gravitational-wave detectors that got us started.