Theoretical development of control devices to manipulate and prepare the motion and the internal state of ultra-cold atoms
Final Report Abstract
Currently, there is much interest in controlling the motion of cold atoms motivated by fundamental physical phenomena, quantum information processing, atom laser generation, metrology, interferometry, or the achievement of lower temperatures. Cold atoms are relatively easy to produce and offer many possibilities for coherent manipulation with lasers, magnetic fields, or mechanical interactions.. They may be trapped in artificial lattices, can be guided in effectively one-dimensional wires, adopt interesting collective behavior, and their mutual interactions can be controlled. All this fiexibility facilitates the translation of some of the concepts and applications of electronic circuits into the atom-optical realm, for example in analogy with the electronic diode, an atom diode, a laser device which lets the neutral atom in its ground state pass in one direction but not in the opposite direction. During this project, we have developed an application of this atom diode to cool and trap atoms on a ring. Another question was the following: if one has a gas of atoms trapped in a harmonic potential and one is imprinting an unknown phase on half of the trap by illumination it with a detuned laser, is it possible to measure the phase from the momentum distribution of the atoms? We have shown that this actually works and might lead to a new and promising method for momentum-space interferometry. An important milestone was the surprising discovery that there is a trajectory,such that a wall moving along it stops a classical particle independent of its velocity by collision, or, put differently, a whole ensemble of particles with a velocity distribution can be stopped. We have generalized this idea, which we have named "quantum catcher", to the stopping of quant um-mechanical particles and especially have shown that is is superior to a linear-in-time trajectory used in current experiments. Another milestone was the discovery of a shortcut to adiabaticity. An adiabatic expansion of a harmonic trap can be used to reduce the energy of the trapped particles. The main problem is that for adiabatic processes long times might be needed, which can make them useless or, quite simply, a faster process is preferred, e.g, to increase the repetition rate of a cycle. We have found a new method to achieve a perfect adiabatic expansion of a harmonic trap in an arbitrary short time by imposing a special time-dependence of the trap frequency. The project has lead to six papers published in refereed journals, one of them is even published in Physical Review Letters.
Publications
- "Control of atomic motion with an atom-optical diode on a ring". Journal of Physics B: At. Mol. Opt. Phys, 41, 205503 (2008)
A. Ruschhaupt and J. G. Muga
- "Atom cooling by nonadiabatic expansion", Physical Review A 80, 063421 (2009)
X. Chen, J. G. Muga, A. del Campo and A. Ruschhaupt
- "Frictionless dynamics of Bose-Einstein condensates under fast trap variations". Journal of Physics B: At. Mol. Opt. Phys. 42, 241001 (2009)
. G. Muga, Xi Chen, A. Ruschhaupt and D, Guery-Odelin
- "Momentum-space interferometry with trapped ultracold atoms", Physical Review A 79, 023616 (2009)
A. Ruschhaupt, A, del Campo, and J. G. Muga
- "Stopping particles of arbitrary velocities with an accelerated wall", Physical Review A 80, 023406 (2009)
S. Schmidt, J. G. Muga, and A. Ruschhaupt
- "Fast Optimal Frictionless Atom Cooling in Harmonic Traps: Shortcut to Adiabaticity". Physical Review Letters 104, 063002 (2010)
X, Chen, A. Ruschhaupt, S. Schmidt, A. del Campo, D. Guery-Odelin and J, G. Muga
