We present a compact and robust setup to optically transport ultracold atoms over long distances. Using a focus-tunable Moire lens that has recently appeared on the market, we demonstrate transport of up to a distance of 465 mm. A transfer efficiency of 70% is achieved with negligible temperature change at 11 $mu$K. With its high thermal stability and low astigmatism, the Moire lens is superior to fluid-based varifocal lenses. It is much more compact and stable than a lens mounted on a linear translation stage, allowing for simplified experimental setups.
We present an all-optical method to load 174Yb atoms into a single layer of an optical trap near the surface of a solid immersion lens which improves the numerical aperture of a microscope system. Atoms are transported to a region 20 um below the surface using a system comprised by three optical dipole traps. The optical accordion technique is used to create a condensate and compress the atoms to a width of 120 nm and a distance of 1.8 um away from the surface. Moreover, we are able to verify that after compression the condensate behaves as a two-dimensional quantum gas.
Transporting cold atoms between distant sections of a vacuum system is a central ingredient in many quantum simulation experiments, in particular in setups, where a large optical access and precise control over magnetic fields is needed. In this work, we demonstrate optical transport of cold cesium atoms over a total transfer distance of about $43,$cm in less than $30,$ms. The high speed is facilitated by a moving lattice, which is generated via the interference of a Bessel and a Gaussian laser beam. We transport about $3times 10^6$ atoms at a temperature of a few $mu$K with a transport efficiency of about $75%$. We provide a detailed study of the transport efficiency for different accelerations and lattice depths and find that the transport efficiency is mainly limited by the potential depth along the direction of gravity. To highlight the suitability of the optical-transport setup for quantum simulation experiments, we demonstrate the generation of a pure Bose-Einstein condensate with about $2times 10^4$ atoms. We find a robust final atom number within $2%$ over a duration of $2.5,$h with a standard deviation of $<5%$ between individual experimental realizations.
Simple models of interacting spins play an important role in physics. They capture the properties of many magnetic materials, but also extend to other systems, such as bosons and fermions in a lattice, systems with gauge fields, high-Tc superconductors, and systems with exotic particles such as anyons and Majorana fermions. In order to study and compare these models, a versatile platform is needed. Realizing such a system has been a long-standing goal in the field of ultracold atoms. So far, spin transport has only been studied in the isotropic Heisenberg model. Here we implement the Heisenberg XXZ model with adjustable anisotropy and use this system to study spin transport far from equilibrium after quantum quenches from imprinted spin helix patterns. In the non-interacting XX model, we find ballistic behavior of spin dynamics, while in the isotropic XXX model, we find diffusive behavior. For positive anisotropies, the dynamics ranges from anomalous super-diffusion to sub-diffusion depending on anisotropy, whereas for negative anisotropies, we observe a crossover in the time domain from ballistic to diffusive transport. This behavior contrasts with expectations for the linear response regime and raises new questions in understanding quantum many-body dynamics far away from equilibrium.
We report the experimental observation of tunable, non-reciprocal quantum transport of a Bose-Einstein condensate in a momentum lattice. By implementing a dissipative Aharonov-Bohm (AB) ring in momentum space and sending atoms through it, we demonstrate a directional atom flow by measuring the momentum distribution of the condensate at different times. While the dissipative AB ring is characterized by the synthetic magnetic flux through the ring and the laser-induced loss on it, both the propagation direction and transport rate of the atom flow sensitively depend on these highly tunable parameters. We demonstrate that the non-reciprocity originates from the interplay of the synthetic magnetic flux and the laser-induced loss, which simultaneously breaks the inversion and the time-reversal symmetries. Our results open up the avenue for investigating non-reciprocal dynamics in cold atoms, and highlight the dissipative AB ring as a flexible building element for applications in quantum simulation and quantum information.
Ultracold atomic gases have realised numerous paradigms of condensed matter physics where control over interactions has crucially been afforded by tunable Feshbach resonances. So far, the characterisation of these Feshbach resonances has almost exclusively relied on experiments in the threshold regime near zero energy. Here we use a laser-based collider to probe a narrow magnetic Feshbach resonance of rubidium above threshold. By measuring the overall atomic loss from colliding clouds as a function of magnetic field, we track the energy-dependent resonance position. At higher energy, our collider scheme broadens the loss feature, making the identification of the narrow resonance challenging. However, we observe that the collisions give rise to shifts in the centre-of-mass positions of outgoing clouds. The shifts cross zero at the resonance and this allows us to accurately determine its location well above threshold. Our inferred resonance positions are in excellent agreement with theory.