Project A4:
Tunable decoherence in atomic quantum dots (2005-2009)
Summary
In this joint project we will explore experimentally and theoretically atomic quantum dot (AQD) systems with the aim to probe and influence the effects of decoherence. AQDs are based on degenerate atomic quantum gases in optical potentials and serve as model systems for solid state quantum impurity problems. One atom in a specific internal state within a strongly confining optical potential forms the AQD and is used as a quantum optical probe for decoherence processes that are induced by the presence of a Bose-Einstein condensate (BEC) of atoms in a distinct internal state. Therefore, the occupation of the strong optical potential with one or no atom is interpreted as spin S and the BEC mimics the environment E. We will realize such an AQD system and explore dissipation, relaxation and decoherence by studying the dynamics of the spin-boson model for a huge parameter range. Experimentally, S will be driven coherently with lasers and observed via state dependent detection. The coupling between S and E is based on atomic collisions and can be widely tuned using Feshbach resonances. Furthermore, the environment E can be tailored since its density of states can be modified by the trapping potentials. By this, the characteristics of dissipation can be changed from ohmic to super-ohmic. We will form and investigate not only single AQDs but also ensembles of a few coupled AQDs that are coupled to E. Further studies will then be devoted to stochastic resonance phenomena in the quantum regime at ultra-low temperatures.
Project leaders
Prof. Dr. Tilman Pfau, 5. Physikalisches Institut, Universität Stuttgart
Dr. Jürgen Stuhler, TOPTICA Photonics AG, Gräfelfing (München)
Prof. Dr. Ulrich Weiss, Institut für Theoretische Physik II, Universität Stuttgart
Refs & Publications
U. Raitzsch, R. Heidemann, H. Weimer, B. Butscher, P. Kollmann, R Löw, H.P. Büchler, and T. Pfau"Investigation of dephasing rates in an interacting Rydberg gas"
New J. Phys. 11, 055014 (2009); arXiv: 0811.4185 [quant-ph]
M. Müller, I. Lesanovsky, H. Weimer, H. P. Büchler, and P. Zoller
"Mesoscopic Rydberg Gate Based on Electromagnetically Induced Transparency"
Phys. Rev. Lett. 102, 170502 (2009); doi: 10.1103/PhysRevLett.102.170502
E. Paladino, M. Sassetti, G. Falci, and U. Weiss
"Characterization of coherent impurity effects in solid-state qubits"
Phys. Rev. B 77, 041303(R), (2008)
R. Heidemann, U. Raitzsch, V. Bendkowsky, B. Butscher, R. Löw, and T. Pfau
"Rydberg excitation of Bose-Einstein condensates"
Phys. Rev. Lett. 100, 033601 (2008)
U. Raitzsch, V. Bendkowsky, R. Heidemann, B. Butscher, R. Löw, and T. Pfau
"An echo experiment in a strongly interacting Rydberg gas"
Phys. Rev. Lett. 100 , 013002 (2008)
E. Paladino, A.G. Maugeri, M. Sassetti, G. Falci, and U. Weiss
"Structured environments in solid-state systems: crossover from Gaussian to non-Gaussian behaviour"
Physica E 40, 198 (2007)
R. Heidemann, U. Raitzsch, V. Bendkowsky, B. Butscher, R. Löw, L. Santos, and T. Pfau
"Evidence for coherent collective Rydberg excitation in the strong blockade regime"
Phys. Rev. Lett. 99, 163601 (2007)
E. Paladino, M. Sassetti, G. Falci, and U. Weiss
"Pure dephasing due to damped bistable quantum impurities"
Chem. Phys. 322, 98 (2006)
A. Grabowski, R. Heidemann, R. Löw, J. Stuhler, and T. Pfau
"High Resolution Rydberg Spectroscopy of ultracold Rubidium Atoms"
Fortschr. Phys. 54, 765 (2006)
R. Löw, R. Gati, J. Stuhler, and T. Pfau
"Probing the light-induced dipole-dipole interaction in momentum space"
Europhys. Lett. 71, 214 (2005)