Schrödinger Kittens from Optical Back-Action Evasion

John R. Gribbin

Bernard Yurke

Back-action evasion is a measurement technique originally devised to overcome certain limits imposed by quantum mechanics on the sensitivity of gravitational radiation detectors. The technique is, however, more generally applicable and can be used to improve the sensitivity of instrumentation with noise floors much greater than the quantum noise floor. The principle of back-action evasion is described here by means of a simple example. A comparison of back-action evasion with impedance matching is made to clarify when back-action evasion may be useful. Back-action evasion allows one to achieve a sensitivity comparable to that achieved by impedance matching.

Heather M. Hill

Arthur La Porta, R. E. Slusher, B. Yurke

The uncertainty principle in general requires that "back-action" noise is introduced into an optical field after it has been measured, so that the precision of subsequent measurements is progressively reduced. However, it has been shown that one quadrature component of the field can be measured without changing its quantum state; i.e. a quantum nondemolition, or more precisely, a back-action evasion measurement can be performed.

James D. Stein