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Accueil du site > Séminaires > LKB > Synthetic Electric and Magnetic Fields for Ultracold Neutral Atoms

Synthetic Electric and Magnetic Fields for Ultracold Neutral Atoms

Séminaire de William Phillips (NIST, Gaithersburg)

Vendredi 19 novembre 2010, 9h15 dans la SALLE DES ACTES à l’ENS au 45 rue d’Ulm

ABSTRACT

Quantum degenerate neutral atomic gases have allowed the simulation of the quantum behavior of a number of models, Hamiltonians, and physical systems. One of the difficulties facing the simulation of certain interesting Hamiltonians with neutral atoms is in simulating the response of charged particles to external electromagnetic fields, particularly to magnetic fields. One approach has been to use rotation, where the Coriolis force mimics the Lorentz force. Another approach, discussed here, involves the simulation of a magnetic vector potential. The idea is that the Hamiltonian for a charged particle in a magnetic vector potential can be written as : H = (p-qA)^2/2m. The introduction of a vector potential is equivalent to displacing the particle’s energy-momentum dispersion curve.

Using a Bose-Einstein condensate of 87Rb atoms we produce an effective vector potential by coupling together different magnetic sublevels using Raman transitions that also transfer linear momentum to the atoms. This shifts the position of the minimum of the atoms’ dispersion curve, creating a non-zero, uniform, effective vector potential. A gradient of a true magnetic field shifts the Raman resonance in a space-dependent manner creating a curl of the effective vector potential and hence a synthetic magnetic field. This magnetic field creates vortices in the Rb cloud, just as if the cloud had been rotating. We have also extended the analog with a magnetic vector potential, producing a synthetic electric field from a time-varying effective vector potential. We measure the effect of this synthetic E-field on both the canonical and mechanical atomic momentum.

We hope to use the synthetic field approach to simulate Quantum Hall and Fractional Quantum Hall effects in our neutral bosonic system.

Post-scriptum :

La salle des actes se trouve dans le bâtiment principal de l’école au 45 rue d’Ulm, Paris 15e

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