Applied Physics

Calling for a Quantum Hush

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Science  01 Oct 2010:
Vol. 330, Issue 6000, pp. 13
DOI: 10.1126/science.330.6000.13-c

Too loud out there?

CREDIT: ISTOCKPHOTO.COM

Coupling the mechanical and optical degrees of freedom of a system, in for example an atomic force microscope, provides the ability to measure displacements on exquisitely small length scales and to image surface height variations of just a single atom. As the systems are designed with better sensitivity (as required for the potential detection of gravity waves in large interferometers) noise can become an increasingly dominant issue. This noise can arise from back-action, whereby the radiation pressure caused by the probe light can perturb the motion of the mechanical system. Optomechanical systems are now entering a sensitivity regime where the light and mechanical motion can be described quantum-mechanically. In analogy to the operation of noise reduction headphones, which record the ambient noise and then play it back with the amplitude negated to prompt destructive interference, Tsang and Caves propose a route to develop quantum noise cancellation for applications in optomechanical sensor systems. They break the problem down into a number of components and in a flowchart representation deal with each component separately, introducing an anti-noise path. In their admittedly idealized system they show how such an approach can deal with the back-action noise and should lead ultimately to improved sensors.

Phys. Rev. Lett. 105, 123601 (2010).

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