Non destructive photon counting and quantum feedback experiments in Cavity Quantum Electrodynamics

TYPETheor./Math. Physics Seminar
Speaker:Prof. S. Haroche
Parent Event:Fundamental tests of quantum physics with atoms and photons in a box.
Location:Lewiner Seminar Room (412)
Abstract:Cavity Quantum Electrodynamics (CQED) – in the spirit of the "photon box" thought experiment imagined by Bohr and Einstein – illustrates the fundamental principles of quantum theory. A beam of Rydberg atoms is used to manipulate and probe non-destructively microwave photons trapped in a very high-Q superconducting cavity. We realize ideal quantum non-demolition (QND) measurements of photon numbers, observe the radiation quantum jumps due to cavity relaxation and prepare non-classical fields such as photon number states (Fock states) and Schrödinger cat states. The reconstruction of these states and the study of their evolution, either spontaneous, or controlled by quantum feedback procedures, provides a striking illustration of the phenomenon of decoherence responsible for the transition from the quantum to the classical worlds. The colloquium will present a broad overview and the two specialized lectures will give more details on specific aspects of this research which may find applications in quantum information.