Observation of backaction-evading measurement of an optical intensity in a three-level atomic nonlinear system

Philippe Grangier (1) , Jean-François Roch (1) , Gérard Roger (1)

1 Laboratoire Charles Fabry de l'Institut d'Optique / Optique quantique

Backaction-evading measurement of an optical intensity has been observed, using a three-level system in a sodium atomic beam as a nonlinear medium. The principle of this experiment is to use the cross-phase-modulation effect, which in principle allows one to read nondestructively the quantum intensity fluctuations of the ''signal'' beam when detecting the phase fluctuations of the ''meter'' beam. Using a cavity-enhancement scheme, the quantum noise measured when recombining the signal and meter photocurrents is 0.8 dB below the shot-noise level.

Domains: Quantum Physics [quant-ph]

Philippe Grangier, Jean-François Roch, Gérard Roger. Observation of backaction-evading measurement of an optical intensity in a three-level atomic nonlinear system. Physical Review Letters, 1991, 66, pp.1418-1421. ⟨10.1103/PhysRevLett.66.1418⟩. ⟨hal-00559097⟩