title: Freezing coherent field growth in a cavity by the quantum zeno effect.
abstract: We have frozen the coherent evolution of a field in a cavity by repeated measurements of its photon number. We use circular Rydberg atoms dispersively coupled to the cavity mode for an absorption-free photon counting. These measurements inhibit the growth of a field injected in the cavity by a classical source. This manifestation of the quantum Zeno effect illustrates the backaction of the photon number determination onto the field phase. The residual growth of the field can be seen as a random walk of its amplitude in the two-dimensional phase space. This experiment sheds light onto the measurement process and opens perspectives for active quantum feedback.
authors.affiliation: Laboratoire Kastler Brossel, Ecole Normale Supérieure, CNRS, Université P. et M. Curie, 24 rue Lhomond, F-75231 Paris Cedex 05, France.
authors.forename: J
authors.initials: J
authors.lastname: Bernu
authors.forename: S
authors.initials: S
authors.lastname: Deléglise
authors.forename: C
authors.initials: C
authors.lastname: Sayrin
authors.forename: S
authors.initials: S
authors.lastname: Kuhr
authors.forename: I
authors.initials: I
authors.lastname: Dotsenko
authors.forename: M
authors.initials: M
authors.lastname: Brune
authors.forename: J M
authors.initials: JM
authors.lastname: Raimond
authors.forename: S
authors.initials: S
authors.lastname: Haroche