Semiclassical limit Bose-Einstein condensate dynamics

• Applicants: Professor Dr. Markus Kurt Oberthaler; Privatdozent Dr. Sandro Wimberger
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 24367642

• Final Report Year: 2014

Final Report Abstract

Ultracold Bose gases have proven to be an ideal experimental test bed for many different contexts. The theoretical description of interacting Bose gases in designed spatial time-dependent potentials is very challenging. In this project, both aspects have been addressed. On the experimental side different breakthroughs have been achieved. While the results on spin changing collisions and the demonstration of coherent matterwave beamsplitter by spontaneous emission have received international visibility (published in the Nature journal and Nature physics journal) the underlying physics cannot be captured by semiclassics nevertheless the have been possible due to the funding by the DFG. A major breakthrough motivated by the research within this research consortium is the successful demonstration of counting mesoscopic atom numbers with single particle accuracy. Up to 1200 atoms have been detected with single particle resolution. The recent results on dynamics in a driven quantum dimer are conclusive and reveal the behavior predicted by the semiclassical description. We could show the basics features of the Poincare Birkhoff scenario by carefully analysing the dynamics of the distribution function and especially the temporal evolution of the variance. Additional the situation of mixed phase space was studied and the basic properties of chaotic sea, transporting island and stationary islands have been demonstrated. Semiclassical methods prove very powerful in many fields of physics. In the context of ultracold bosons, one semiclassical limit is the mean-field description valid for small interactions and large particle numbers. In our project we developed efficient methods how to go beyond mean-field in the solution of dynamical and non-equilibrium transport problems of ultracold bosons. Together with exact diagonalisations and respective consistency checks we gained a good understanding about the validity of our methods. The highlight of our work was the finding and characterization of stable many-body structures in dissipative optical lattices. Our results are embedded in the global context of open quantum many-body systems whose implementation with ultracold atoms has just started. Therefore, the here studied setup of particle transport between two reservoirs connected by a Bose-Hubbard chain provides interesting perspectives for future projects in this directions. We could present the project to a broader audience within an article in the Ruperto Carola Research Magazine, Heidelberg University (2011) 3, pp. 44-45.

Publications

• Atomic homodyne detection of continuous variable entangled twin-atom states, Nature 480, 219 (2011)
  C. Gross, H. Strobel, E. Nicklas, T. Zibold, N. Bar-Gill, G. Kurizki and M.K. Oberthaler
  
• Beyond mean-field dynamics in open Bose-Hubbard chains, Phys. Rev. A 83, 063608 (2011)
  D. Witthaut, F. Trimborn, H. Hennig, G. Kordas, T. Geisel, and S. Wimberger
  
• Local and spatially extended sub-Poisson atom-number fluctuations in optical lattices, Phys. Rev. A 84, 011609 (2011)
  C. Gross, J. Esteve, M. K. Oberthaler, A. D. Martin and J. Ruostekoski
  
• Rabi flopping induces spatial demixing dynamics, Phys. Rev. Lett. 107, 193001 (2011)
  E. Nicklas, H. Strobel, T. Zibold, C. Gross, B. A. Malomed, P. G. Kevrekidis and M. K. Oberthaler
  
• Single spontaneous photon as a coherent beamsplitter for an atomic matter-wave, Nature Physics 7, 379 (2011)
  J. Tomkovic, M. Schreiber, J. Welte, M. Kiffner, J. Schmiedmayer, and M.K. Oberthaler
  
• Dissipation induced macroscopic entanglement in an open optical lattice, Europhys. Lett. 100, 30007 (2012)
  G. Kordas, S. Wimberger, and D. Witthaut
  
• Accurate Atom Counting in Mesoscopic Ensembles, Phys. Rev. Lett. 111, 253001 (2013)
  D. B. Hume, I. Stroescu, M. Joos, W. Muessel, H. Strobel, and M. K. Oberthaler
  
• Bosonic transport through a chain of quantum dots, Eur. Phys. J. B 86, 345 (2013)
  A. Ivanov, G. Kordas, A. Komnik, and S. Wimberger
  
• Optimized absorption imaging of mesoscopic atomic clouds, Appl. Phys. B 113, 69 (2013)
  W. Muessel, H. Strobel, M. Joos, E. Nicklas, I. Stroescu, J. Tomkovic, D.B. Hume and M.K. Oberthaler