In the presence of a complex classical dynamics associated with a mixed phase space, a quantum wave function can tunnel between two stable islands through the chaotic sea, an effect that has no classical counterpart. This phenomenon, referred to as c
haos assisted tunneling, is characterized by large fluctuations of the tunneling rate when a parameter is varied. To date the full extent of this effect as well as the associated statistical distribution have never been observed in a quantum system. Here we analyze the possibility of characterizing these effects accurately in a cold atom experiment. Using realistic values of the parameters of an experimental setup, we examine through analytical estimates and extensive numerical simulations a specific system that can be implemented with cold atoms, the atomic modulated pendulum. We assess the efficiency of three possible routes to observe in detail chaos assisted tunneling properties. Our main conclusion is that due to the fragility of the symmetry between positive and negative momenta as a function of quasimomentum, it is very challenging to use tunneling between classical islands centered on fixed points with opposite momentum. We show that it is more promising to use islands symmetric in position space, and characterize the regime where it could be done. The proposed experiment could be realized with current state-of-the-art technology.
We explore the manipulation in phase space of many-body wavefunctions that exhibit self-similar dynamics, under the application of sudden force and/or in the presence of a constant acceleration field. For this purpose, we work out a common theoretica
l framework based on the Wigner function. We discuss squeezing in position space, phase space rotation and its implications in cooling for both non-interacting and interacting gases, and time reversal operation. We discuss various optical analogies and calculate the role of spherical-like aberration in cooling protocols. We also present the equivalent of a spin-echo technique to improve the robustness of velocity dispersion reduction protocols.
We present measurements of the hyperfine coefficients and isotope shifts of the Dy I $683.731 $nm transition, using saturated absorption spectroscopy on an atomic beam. A King Plot is drawn resulting in an updated value for the specific mass shift $d
elta u_mathrm{684,sms}^mathrm{164-162}=-534 pm 17 MHz$. Using fluorescence spectroscopy we measure the excited state lifetime $tau_{684}=1.68(5) mu$s, yielding a linewidth of $gamma_mathrm{684} = 95 pm 3 kHz$. We give an upper limit to the branching ratio between the two decay channels from the excited state showing that this transition is useable for optical pumping into a dark state and demagnetization cooling.
We report on the observation of the confinement-induced collapse dynamics of a dipolar Bose-Einstein condensate (dBEC) in a one-dimensional optical lattice. We show that for a fixed interaction strength the collapse can be initiated in-trap by loweri
ng the lattice depth below a critical value. Moreover, a stable dBEC in the lattice may become unstable during the time-of-flight dynamics upon release, due to the combined effect of the anisotropy of the dipolar interactions and inter-site coherence in the lattice.
