Electromagnetically-induced transparency and entanglement dynamics of a strongly driven trapped atom

• Antragsteller: Professor Dr. Hanspeter Helm
• Fachliche Zuordnung: Optik, Quantenoptik und Physik der Atome, Moleküle und Plasmen
• Förderung: Förderung von 2010 bis 2011
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 168164125

• Erstellungsjahr: 2011

Zusammenfassung der Projektergebnisse

We have studied the entanglement dynamics in EIT laser cooling of trapped atoms, employing the negativity as a measure for entanglement. We have demonstrated that essential features of the dynamical behavior of the negativity can be explained in terms of a conceptually simple model which is based on Landau-Zener state pairs at avoided crossings in the spectrum of the full atom-field Hamiltonian. As we have seen by the comparison with numerical simulations of the full master equation, the model correctly describes the entanglement oscillations and their decay in the early stage of the cooling process, as well as the revival of entanglement towards the final stationary state of the atom. While these features can be explained qualitatively and quantitatively on the basis of the Landau-Zener model, a deeper understanding of other features, like the observed power law decay of negativity and its precipitous drop in the transient regime of cooling, is still lacking. This requires a more sophisticated treatment of the dynamical transfer of negativity between different Landau-Zener state pairs induced by spontaneous emission processes. The theoretical picture developed in this project points towards fundamental distinctions between the entanglement which is generated by laser cooling of atoms in the EIT scheme investigated here, and that based on velocity-selective coherent population trapping of free atoms on the other hand. We have investigated schemes for the freezing of the entanglement between internal and external atomic degrees of freedom by controlled turnoff of the laser fields. This scheme may find further interesting applications in the entanglement control of a much more general class of physical systems which are driven by external fields. It appears worthwhile to study in more detail other control methods involving adiabatic turn-on and turn-off, and / or suitably designed pulse shapes and sequences of pulses of the external driving fields.

Projektbezogene Publikationen (Auswahl)

• Dissipative Light Scattering by a Trapped Atom approaching EIT Conditions. Phys. Rev. A 81, 033418 (2010)
  M. Roghani, H.-P. Breuer and H. Helm
  
• Dynamics of entanglement between internal and external degrees of freedom in EIT cooling. Quantum Efficiency Colloquium, Freiburg Institute of Advanced Studies, June 2010
  M. Roghani
  
• Entanglement and Quantum Correlations. Quantum Efficiency Seminar, Freiburg Institute for Advanced Studies, April 2010
  H.-P. Breuer
  
• Entanglement between internal and external degrees of freedom of a driven trapped atom. Physica Scripta T140, 014034 (2010)
  M. Roghani, H. Helm and H.-P. Breuer
  
• Memory and Information Flow in Open Quantum Systems. Institute for Theoretical Physics, University of Göttingen, May 2010
  H.-P. Breuer
  
• Memory and Information Flow in Open Quantum Systems. International Workshop on Statistical Physics of Quantum Systems, University of Tokyo, Japan, August 2010
  H.-P. Breuer
  
• Memory and Information Flow in Open Quantum Systems. University of Ulm, November 2010
  H.-P. Breuer
  
• Memory and Information Flow in Open Quantum Systems. Workshop on Quantum Mechanics: Foundations and Open Systems, University of Turku, Finland, October 2010
  H.-P. Breuer
  
• Entanglement dynamics of a strongly driven trapped atom. Phys. Rev. Lett. 106, 040502 (2011)
  M. Roghani, H. Helm and H.-P. Breuer
  
• Quantum measures for non-Markovianity. Institute for Theoretical Physics, University of Innsbruck, July 2011
  H.-P. Breuer