Synopsis: Turning backaction around

Signal amplification in an optical interferometer may push the sensitivity of measurements beyond the standard quantum limit.
Synopsis figure
Illustration: Courtesy of A. Heidmann, Laboratoire Kastler Brossel

Optical techniques that have been developed to measure small displacements are important for gravitational wave astronomy, the detection of currents in superconductors, and the study of quantum effects in mechanical systems. Optical interferometry is unsurpassed in its ability to detect small displacements, but runs into a sensitivity limit known as the standard quantum limit, which results from quantum fluctuations in the light probe itself disturbing the object being measured.

In a paper appearing in Physical Review Letters, Pierre Verlot and colleagues at Laboratoire Kastler Brossel in Paris demonstrate that radiation pressure induced “backaction” fluctuations of the mirror position in an optical interferometer can amplify a signal imprinted on the interferometer light. An amplification factor greater than six was observed by tuning the signal modulation frequency close to the frequency of a cavity mechanical resonance. Although the sensitivity of the current experiment was limited by thermal noise, the amplification technique has the potential to surpass the standard-quantum limit, which would open up new frontiers in precision optical interferometry. – Mark Saffman


Features

More Features »

Announcements

More Announcements »

Subject Areas

Quantum InformationOptics

Previous Synopsis

Fluid Dynamics

Drying out in 3D

Read More »

Next Synopsis

Related Articles

Focus: Atomic Impersonator
Optics

Focus: Atomic Impersonator

Calculations show that a carefully engineered laser pulse can induce an atom to emit light as if it were a different atom. Read More »

Viewpoint: Transportable Clocks Move with the Times
Optics

Viewpoint: Transportable Clocks Move with the Times

Transportable atomic clocks are now operating with fractional-frequency uncertainties below one part in 1016, opening up new applications. Read More »

Synopsis: Superdense Coding over Optical Fiber
Quantum Information

Synopsis: Superdense Coding over Optical Fiber

Researchers have demonstrated the fiber transmission of quantum information in which each quantum bit carries nearly two bits of classical information. Read More »

More Articles