arXiv subjects

Alexander Herbst

Publications and source records attributed to Alexander Herbst.

5 recordsLinked to original sources

arXiv2024

Matter-wave collimation to picokelvin energies with scattering length and potential shape control

The sensitivity of atom interferometers depends on their ability to realize long pulse separation times and prevent loss of contrast by limiting the expansion of the atomic ensemble within the interferometer beam through matter-wave collimation. Here we investigate the impact of atomic interactions on collimation by applying a lensing protocol to a $^{39}$K Bose-Einstein condensate at different scattering lengths. Tailoring interactions, we measure energies corresponding to $340 \pm 12$ pK in one direction. Our results are supported by an accurate simulation, which allows us to extrapolate a 2D ballistic expansion energy of $438 \pm 77$ pK. Based on our findings we propose an advanced scenario, which enables 3D expansion energies below $16$ pK by implementing an additional pulsed delta-kick. Our results pave the way to realize ensembles with more than $1\times10^5$ atoms and 3D energies in the two-digit pK range in typical dipole trap setups without the need for micro-gravity or long baseline environments.

physics.atom-ph↗

arXiv2023

A high-flux source system for matter-wave interferometry exploiting tunable interactions

Atom interferometers allow determining inertial effects to high accuracy. Quantum-projection noise as well as systematic effects impose demands on large atomic flux as well as ultra-low expansion rates. Here we report on a high-flux source of ultra-cold atoms with free expansion rates near the Heisenberg limit directly upon release from the trap. Our results are achieved in a time-averaged optical dipole trap and enabled through dynamic tuning of the atomic scattering length across two orders of magnitude interaction strength via magnetic Feshbach resonances. We demonstrate BECs with more than $6\times 10^{4}$ particles after evaporative cooling for $170$ ms and their subsequent release with a minimal expansion energy of $4.5$ nK in one direction. Based on our results we estimate the performance of an atom interferometer and compare our source system to a high performance chip-trap, as readily available for ultra-precise measurements in micro-gravity environments.

cond-mat.quant-gas↗

arXiv2022

Rapid generation of all-optical $^{39}$K Bose-Einstein condensates using a low-field Feshbach resonance

Ultracold potassium is an interesting candidate for quantum technology applications and fundamental research as it allows controlling intra-atomic interactions via low-field magnetic Feshbach resonances. However, the realization of high-flux sources of Bose-Einstein condensates remains challenging due to the necessity of optical trapping to use magnetic fields as free parameter. We investigate the production of all-optical $^{39}$K Bose-Einstein condensates with different scattering lengths using a Feshbach resonance near $33$ G. By tuning the scattering length in a range between $75\, a_0$ and $300\, a_0$ we demonstrate a trade off between evaporation speed and final atom number and decrease our evaporation time by a factor of $5$ while approximately doubling the evaporation flux. To this end, we are able to produce fully condensed ensembles with $5.8\times10^4$ atoms within $850$ ms evaporation time at a scattering length of $232\, a_0$ and $1.6\times10^5$ atoms within $3.9$ s at $158\, a_0$, respectively. We deploy a numerical model to analyse the flux and atom number scaling with respect to scattering length, identify current limitations and simulate the optimal performance of our setup. Based on our findings we describe routes towards high-flux sources of ultra-cold potassium for inertial sensing.

cond-mat.quant-gas↗

arXiv2021

The Antenna Base Plays a Crucial Role in Mosquito Courtship Behavior

Mosquitoes are vectors of diseases like malaria, dengue fever, yellow fever, chikungunya and Zika. For mosquito control it is crucial to understand their hearing system, as mosquitoes' courting behavior is mostly auditory. Many nonlinear characteristics of the mosquito hearing organ have been observed through behavioral studies and neural measurements. These enable mosquitoes to detect and synchronize to other mosquitoes. Many hypotheses concerning the role of the flagellum and the fibrillae of the antenna in mosquito hearing have been made, and neural processes have been considered as the origin of the nonlinearities. In this study we introduce a geometric model based on the morphology of the mosquito antenna base. The model produces many of the observed nonlinear characteristics, providing evidence that the base of the antenna plays a crucial role in mosquito hearing. Even without neural processing, the antenna response to sound produces behaviorally relevant cues that can inform about the presence, location and sex of other mosquitoes.

nlin.AO↗

arXiv2021

Red- and blue-detuned magneto-optical trapping with liquid crystal variable retarders

We exploit red- and blue-detuned magneto optical trapping (MOT) of $^{87}$Rb benefitting from a simplified setup based on liquid crystal variable retarders (LCVR). To maintain the trapping forces when switching from a red- to a blue-detuned MOT, the circularity of the cooling beams needs to be reversed. LCVRs allow fast polarization control and represent compact, simple and cost-efficient components which can easily be implemented in existing laser systems. This way, we achieve a blue-detuned type-II MOT for $^{87}$Rb atoms with sub-Doppler temperatures of 44.5 $μ$K. The phase space density is increased by more than two orders of magnitude compared to the standard red-detuned type-I MOT. The setup can readily be transferred to any other system working with $^{87}$Rb.

physics.atom-ph↗