Düsseldorf 2007 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 41: Quanteninformation (Konzepte II)
Q 41.8: Vortrag
Mittwoch, 21. März 2007, 15:45–16:00, 5L
Coherent control in a decoherence-free subspace of a collective multi-level system — •Martin Kiffner, Jörg Evers, and Christoph H. Keitel — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
Decoherence-free subspaces (DFS) in a system of two dipole-dipole interacting multi-level atoms are investigated theoretically. The ground state of each atom is a S0 singlet state, and the excited state multiplet is a P1 triplet which consists of three Zeeman sublevels. Since we consider arbitrary geometrical alignments of the atoms, all Zeeman sublevels of the atomic multiplets have to be taken into account [1]. It is shown that the collective state space of the two dipole-dipole interacting four-level atoms contains a four-dimensional DFS [2]. We describe a method that allows to populate the antisymmetric states of the DFS by means of a laser field, without the need of a field gradient between the two atoms. These antisymmetric states are identified as long-lived entangled states. Further, we show that any single-qubit operation between two states of the DFS can be induced by means of a microwave field. Typical operation times of these qubit rotations can be significantly shorter than for a nuclear spin system.
[1] M. Kiffner, J. Evers, and C. H. Keitel, arXiv:quant-ph/0611071.
[2] M. Kiffner, J. Evers, and C. H. Keitel, arXiv:quant-ph/0611084.