Robert Niffenegger

Tunable Landau-Zener transitions in a spin-orbit-coupled Bose-Einstein condensate

The Landau-Zener (LZ) transition is one of the most fundamental phenomena in quantum dynamics. It describes nonadiabatic transitions between quantum states near an avoided crossing that can occur in diverse physical systems. Here we report experimental measurements and tuning of LZ transitions between the dressed eigenlevels of a Bose-Einstein condensate (BEC) that is synthetically spin-orbit (SO) coupled. We measure the transition probability as the BEC is accelerated through the SO avoided crossing and study its dependence on the coupling between the diabatic (bare) states, eigenlevel slope, and eigenstate velocity--the three parameters of the LZ model that are independently controlled in our experiments. Furthermore, we performed time-resolved measurements to demonstrate the breaking down of the spin-momentum locking of the spin-orbit-coupled BEC in the nonadiabatic regime, and we determined the diabatic switching time of the LZ transitions. Our observations show quantitative agreement with the LZ model and numerical simulations of the quantum dynamics in the quasimomentum space. The tunable LZ transition may be exploited to enable a spin-dependent atomtronic transistor.

Optimizing the efficiency of evaporative cooling in optical dipole traps

We present a combined computational and experimental study to optimize the efficiency of evaporative cooling for atoms in optical dipole traps. By employing a kinetic model of evaporation, we provide a strategy for determining the optimal relation between atom temperature, trap depth, and average trap frequency during evaporation given experimental initial conditions. We then experimentally implement a highly efficient evaporation process in an optical dipole trap, showing excellent agreement between the theory and experiment. This method has allowed the creation of pure Bose-Einstein condensates of

Stueckelberg interferometry using periodically driven spin-orbit-coupled Bose-Einstein condensates

^{87}

Spin Current Generation and Relaxation in a Quenched Spin-Orbit Coupled Bose-Einstein Condensate.

Rb with 2

Engineering an atom-interferometer with modulated light-induced

\times 10^4

3 \pi

atoms starting from only

spin-orbit coupling

5\times 10^5

Experimental studies of collective excitations of a BEC in light-induced gauge fields

atoms initially loaded in the optical dipole trap, achieving an evaporation efficiency,

Transport behaviors of BEC in synthetic spin-orbit and gauge fields

\gamma_{eff}

Spin Transport in Spin Orbit Coupled Bose Einstein Condensates

, of 4.0 during evaporation.