G. Nandi

Bose-Einstein Condensation in Microgravity

Going Down the Tube Two pillars of modern physics are quantum mechanics and general relativity. So far, both have remained apart with no quantum mechanical description of gravity available. Van Zoest et al. (p. 1540; see the Perspective by Nussenzveig and Barata) present work with a macroscopic quantum mechanical system—a Bose-Einstein condensate (BEC) of rubidium atoms in which the cloud of atoms is cooled into a collective quantum state—in microgravity. By dropping the BEC down a 146-meter-long drop chamber and monitoring the expansion of the quantum gas under these microgravity conditions, the authors provide a proof-of-principle demonstration of a technique that can probe the boundary of quantum mechanics and general relativity and perhaps offer the opportunity to reconcile the two experimentally. Studies of atomic quantum states in free-fall conditions may provide ways to test predictions of general relativity. Albert Einstein’s insight that it is impossible to distinguish a local experiment in a “freely falling elevator” from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

Dropping cold quantum gases on Earth over long times and large distances

We analyze the evolution of a degenerate quantum gas (bosons and fermions) falling in Earths gravity during long times

Realization of a magneto-optical trap in microgravity

(10\phantom{\rule{0.3em}{0ex}}\mathrm{s})

RUBIDIUM BOSE–EINSTEIN CONDENSATE UNDER MICROGRAVITY

and over large distances

ATOMIC QUANTUM SENSORS IN SPACE

(100\phantom{\rule{0.3em}{0ex}}\mathrm{m})

Developments toward atomic quantum sensors

. This models an experiment that is currently performed by the QUANTUS Collaboration at ZARM drop tower in Bremen, Germany. Starting from the classical mechanics of the drop capsule and a single particle trapped within, we develop a quantum field theoretical description for this experimental situation in an inertial frame, the corotating frame of the Earth, as well as the comoving frame of the drop capsule. Suitable transformations eliminate noninertial forces, provided all external potentials (trap, gravity) can be approximated with a second-order Taylor expansion around the instantaneous trap center. This is an excellent assumption, and the harmonic potential theorem applies. As a first application, we study the quantum dynamics of a cigar-shaped Bose-Einstein condensate in the Gross-Pitaevskii mean-field approximation. Due to the instantaneous transformation to the rest frame of the superfluid wave packet, the long-distance drop can be studied easily on a numerical grid.

Collective Feshbach scattering of a superfluid droplet from a mesoscopic two-component Bose-Einstein condensate

We report on the first realization of magneto-optically cooled atoms in microgravity as a first result of the collaboration project ATKAT (atom catapult). We present the compact and robust setup for cooling and trapping neutral 87Rb atoms in microgravity conditions in the drop tower in Bremen⊥ and discuss the specific requirements the setup has to meet. In particular we present a small size and mechanically stable laser system and discuss the specifics of the ultra high vacuum chamber. A free falling magneto-optical trap (MOT) as realized in this project provides a basis for further experiments which aim at investigating cold quantum matter in microgravity. ⊥www.zarm.uni-bremen.de

QUANTUS - degenerate quantum gases in microgravity

Weightlessness promises to substantially extend the science of quantum gases toward presently inaccessible regimes of low temperatures, macroscopic dimensions of coherent matter waves, and enhanced duration of unperturbed evolution. With the long-term goal of studying cold quantum gases on a space platform, we currently focus on the implementation of an 87Rb Bose–Einstein condensate (BEC) experiment under microgravity conditions at the ZARM drop tower in Bremen (Germany). Special challenges in the construction of the experimental setup are posed by a low volume of the drop capsule (< 1 m3) as well as critical vibrations during capsule release and peak decelerations of up to 50 g during recapture at the bottom of the tower. All mechanical and electronic components have thus been designed with stringent demands on miniaturization, mechanical stability and reliability. Additionally, the system provides extensive remote control capabilities as it is not manually accessible in the tower two hours before and during the drop. We present the robust system and show results from first tests at the drop tower.

Bose–Einstein condensates in microgravity

In this article we present actual projects concerning high resolution measurements developed for future space missions based on ultracold atoms at the Institut fur Quantenoptik (IQ) of the University of Hannover. This work involves the realization of a Bose–Einstein condensate in a microgravitational environment and of an inertial atomic quantum sensor.

A freely falling magneto-optical trap drop tower experiment

In this proceeding we present ongoing projects concerning high resolution measurements developed for future space missions based on ultracold atoms at the Institut fur Quantenoptik (IQ) of the Leibniz-Universitat Hannover. This work involves the realization of a Bose Einstein condensate in microgravitational environment and an inertial atomic quantum sensor.