Total control over ultracold interactions via electric and magnetic fields

The scattering length is commonly used to characterize the strength of ultracold atomic interactions, since it is the leading parameter in the low-energy expansion of the scattering phase shift. Its value can be modified via a magnetic field, by using a Feshbach resonance. However, the effective range term, which is the second parameter in the phase shift expansion, determines the width of the resonance and gives rise to important properties of ultracold gases. Independent control over this parameter is not possible by using a magnetic field only. We demonstrate that a combination of magnetic and electric fields can be used to get independent control over both parameters, which leads to full control over elastic ultracold interactions.Comment: 4 pages, 3 figure

Dissociation of Feshbach Molecules into Different Partial Waves

Ultracold molecules can be associated from ultracold atoms by ramping the magnetic field through a Feshbach resonance. A reverse ramp dissociates the molecules. Under suitable conditions, more than one outgoing partial wave can be populated. A theoretical model for this process is discussed here in detail. The model reveals the connection between the dissociation and the theory of multichannel scattering resonances. In particular, the decay rate, the branching ratio, and the relative phase between the partial waves can be predicted from theory or extracted from experiment. The results are applicable to our recent experiment in 87Rb, which has a d-wave shape resonance.Comment: Added Refs.[32-38

Reinforcement Learning of a Pneumatic Robot Arm Controller

We applied Reinforcement Learning (RL) on a real robot arm actuated by two pneumatic artificial muscles that expose a highly nonlinear behaviour. To facilitate learning, we developed an empirical model based on real robot observations. Using the learned simulation model, reinforcement learning was able to quickly learn good robot controllers. 1

Laser cooling and the highest bound states of the Na diatom system

Using a multichannel bound-state method we predict the highest bound states of the 23Na diatom system, which are closely related to the collisional behavior of ultracold atoms. The results agree well with a model where the hyperfine interaction is treated in first-order perturbation theory, except for the triplet level closest to the continuum, which we predict to be very weakly bound. This level is responsible for the large, positive scattering length of the mf=±f states of the lower hyperfine manifold. Its experimental observation would confirm our prediction of a stable Bose condensate

Time-dependent Feshbach resonance scattering and anomalous decay of a Na Bose-Einstein condensate

We study Feshbach resonance scattering in a time-dependent magnetic field. We explain the extremely rapid decay observed in a recent experiment investigating Feshbach resonances in a Na Bose-Einstein condensate. In our picture, the decay is stimulated by the formation of a molecular condensate of quasibound atom pairs. Another essential element is the concept of a global and a local resonance lifetime. The predicted decay rates are large, about 5 orders of magnitude larger than typical dipole decay rates, and 1 order larger than typical exchange decay rates. We point out the possible role of a Josephson-like oscillation between the atomic condensate and a long-range molecular condensate

Stability limit of the cryogenic hydrogen maser

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Unstable oscillation of the cryogenic H Maser

SCOPUS: ar.jinfo:eu-repo/semantics/publishe