M. Gärttner

Publications (4)3.57 Total impact

• Article: Finite-size effects in strongly interacting Rydberg gases

  M. Gärttner, K. P. Heeg, T. Gasenzer, J. Evers
  [show abstract] [hide abstract]
  ABSTRACT: The scaling of the number of Rydberg excitations in a laser-driven cloud of atoms with the interaction strength is found to be affected by the finite size of the system. The scaling predicted by a theoretical model is compared with results extracted from a numerical many-body simulation. We find that the numerically obtained scaling exponent in general does not agree with the analytical prediction. By individually testing the assumptions leading to the theoretical prediction using the results from the numerical analysis, we identify the origin of the deviations, and explain it as arising from the finite size of the system. Furthermore, finite-size effects in the pair correlation function $g^{(2)}$ are predicted. Finally, in larger ensembles, we find that the theoretical predictions and the numerical results agree, provided that the system is sufficiently homogeneous.
  05/2012;
• Article: Optimal self-assembly of Rydberg excitations for quantum gate operations

  M. Gärttner, K. P. Heeg, T. Gasenzer, J. Evers
  [show abstract] [hide abstract]
  ABSTRACT: We study off resonantly driven disordered gases of Rydberg atoms showing that strong correlation and non-trivial spatial ordering of excitations arise. As an application an implementation of the three-atom CSWAP or Fredkin gate with Rydberg atoms is discussed. The gate not only exploits the Rydberg blockade, but also utilizes the special features of an asymmetric geometric arrangement of the three atoms. We show that continuous-wave off-resonant laser driving alone is sufficient to create Rydberg excitations in the required spatial arrangement out of a homogeneous cloud of atoms, thus optimizing the gate fidelity automatically.
  03/2012;
• Source

  Available from: ArXiv

  Article: A hybrid model for Rydberg gases including exact two-body correlations

  K. P. Heeg, M. Gärttner, J. Evers
  [show abstract] [hide abstract]
  ABSTRACT: A model for the simulation of ensembles of laser-driven Rydberg-Rydberg interacting multi-level atoms is discussed. Our hybrid approach combines an exact two-body treatment of nearby atom pairs with an effective approximate treatment for spatially separated pairs. We propose an optimized evolution equation based only on the system steady state, and a time-independent Monte Carlo technique is used to efficiently determine this steady state. The hybrid model predicts features in the pair correlation function arising from multi-atom processes which existing models can only partially reproduce. Our interpretation of these features shows that higher-order correlations are relevant already at low densities. Finally, we analyze the performance of our model in the high-density case.
  02/2012;
• Source

  Available from: Juan J. Omiste

  Article: Theoretical description of adiabatic laser alignment and mixed-field orientation: the need for a non-adiabatic model.

  J J Omiste, M Gärttner, P Schmelcher, R González-Férez, L Holmegaard, J H Nielsen, H Stapelfeldt, J Küpper
  [show abstract] [hide abstract]
  ABSTRACT: We present a theoretical study of recent laser-alignment and mixed-field-orientation experiments of asymmetric top molecules. In these experiments, pendular states were created using linearly polarized strong ac electric fields from pulsed lasers in combination with weak electrostatic fields. We compare the outcome of our calculations with experimental results obtained for the prototypical large molecule benzonitrile (C(7)H(5)N) [J. L. Hansen et al., Phys. Rev. A, 2011, 83, 023406.] and explore the directional properties of the molecular ensemble for several field configurations, i.e., for various field strengths and angles between ac and dc fields. For perpendicular fields one obtains pure alignment, which is well reproduced by the simulations. For tilted fields, we show that a fully adiabatic description of the process does not reproduce the experimentally observed orientation, and it is mandatory to use a diabatic model for population transfer between rotational states. We develop such a model and compare its outcome to the experimental data confirming the importance of non-adiabatic processes in the field-dressed molecular dynamics.
  Physical Chemistry Chemical Physics 06/2011; 13(42):18815-24. · 3.57 Impact Factor