Quantum Computation and Information Seminar 

14/11/2014, 14:00 — 15:00 — Room P9, Mathematics Building
Jean-Michel Raimond, École Normale Supérieure

Quantum measurement and feedback with atoms and cavities

Quantum non-demolition information on the number of microwave photons stored in a superconducting cavity can be obtained by sending trough the mode circular Rydberg atoms, interacting dispersively with the field. This information can be used to reveal the quantum jumps of light. We will describe an optimal use of this information, based on the past quantum state formalism. Photon number measurement can also be used to stabilize a non-classical photon number state against decoherence, in a quantum feedback process operating in the steady state. Finally, the principle of quantum feedback can be applied to an improved adaptive QND measurement of the photon number. We shall report on these recent experiments and on the perspectives they open for non-classical state manipulations.