(Archives) Vendredi 22 Juillet 2011 à 13h30 (amphi Ponte, institut Fresnel) - Time reversal symmetry in optics – coupling a photon to an atom

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(Archives) Vendredi 22 Juillet 2011 à 13h30 (amphi Ponte, institut Fresnel) - Time reversal symmetry in optics – coupling a photon to an atom

par Gerd Leuchs
Max Planck Institut für die Physik des Lichts,
Universität Erlangen-Nürnberg, Erlangen, Germany


There is a general recipe for achieving optimum coupling of light to resonant optical material systems, such as Fabry Perot resonators, super and sub wavelength antenna structures. The extreme case for the latter is a single atom, which will be treated in detail. This coupling between light and a single atom is probably the most fundamental process in quantum optics. The best strategy for efficiently coupling light to a single atom in free space depends on the goal. If the goal is to maximally attenuate a laser beam, narrow band on resonance laser radiation is required as well as a wave front approaching the atom from a 2pi solid angle. If, on the other hand, the goal is to fully absorb the light bringing the atom to the excited state with its Bloch vector pointing fully upwards one will have to provide a single photon, designed to represent the time reversed wave packet which the atom would emit in a spontane¬ous emission process. Among other conditions this requires the single photon wave packet impinging from a full 4pi solid angle and having the correct temporal shape. Any deviation from the perfect shape will reduce the efficiency. The state of the art is reviewed and the experimental progress is discussed. If the interaction is strong enough it will allow for building a few photon quantum gate without a cavity with possible applications in quantum information processing, such as a quantum repeater.


Prof. Gerd Leuchs is the founding director of the Max Planck Institute (MPI) for the Science of Light in Erlangen and the head of the Optics & Information Division of the MPI. The range of topics that he investigates includes classical optics (optical 3D metrology, interferometry, high-resolution interferometry, etc.) as well as quantum information processing. Prof. Leuchs held the chair of optics at the University of Erlangen-Nuremberg, which is now integrated in the MPL.

Invitation : H. Giovannini, A. Sentenac (SEMO)