Quantum Gases in Microgravity

QUANTUS-Logo-BEC

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Introduction

Within the QUANTUS and BECCAL consortia we are aiming at enabling applications for quantum technologies outside of the laboratory.

This is done in several DLR-funded projects within which different experimental setups are developed for different microgravity platforms ranging from the drop tower in Bremen over suborbital sounding rockets to experiments for the International Space Station (ISS).

The focus of these experiments lies in the realization of robust quantum sensors based on cold and ultra-cold atoms.

To this end we are developing the hardware required to perform those highly delicate experiments in the harsh surroundings of space missions, as well as the scientific techniques that make use of the unique surrounding of weightlessness.

Especially experiments with atom interferometry are aimed for as the precision of those measurements scales quadratically with the interrogation time, which in microgravity is only limited by the expansion velocity of the atomic ensemble. Compared to experiments on ground where the interrogation time is usually limited by the free fall time, this promises for a massively increased precision.

Atom interferometers can be used for the determination of inertial forces like accelerations or rotations, or fundamental constants like the fine structure constant or the gravitational constant. Even applications in the search for gravitational waves are possible.

Technical developments

Renderings of Zerodur-based optical and opto-mechanical components including (a) fiber collimator, (b) fiber coupler, (c) fixed mirror, (d) adjustable mirror, (e) dichroic mirror, (f) polarization beam splitter, (g) waveplate holder, (h) holder for shutter (from J. P. Marburger et al, Proceedings 1118052 (2019))

At the Johannes Gutenberg University Mainz, we are focusing on the development of the required hardware to enable these highly delicate experiments in the harsh surroundings of microgravity, namely the optical systems required for laser cooling, manipulation, atom interferometry and detection.

Thus, we developed a toolset for fiber-coupled optical systems based on the glass ceramic Zerodur initially for the sounding rocket mission MAIUS-1. This toolset was  subsequently extended in the framework of the missions MAIUS-2/3 and BECCAL. Zerodur is a glass ceramic manufactured by SCHOTT AG featuring a vanishing coefficient of thermal expansion as well as a high degree of mechanical robustness, making it suitable as base material for optical systems.

This toolset allows for the realization of intensity switching, overlapping and splitting of different light fields, power monitoring and pulse shaping of pulses in the microsecond range.

It includes optical components like fixed and adjustable mirrors, mounts for waveplates, polarizing beam splitters, acousto-optical modulators, optical isolators, mechanical shutters and photo diodes.

Current Projects

Currently, we are working on three different experiments within the scope of this project

  • QUANTUS-2, a drop-tower experiment.
  • MAIUS-II and MAIUS-III, a sounding rocket experiment and successor of the MAIUS experiment. MAIUS-II will enable dual-species atom interferometry with rubidium and potassium, hereby enabling a high-fidelity test of the weak equivalence principle.
  • The BECCAL experiment is a multi-user experimental facility to be launched to the ISS that will enable a multitude of quantum-optic experiments.

Past Projects

We have successfully completed the following experiments within this project:

  • FOKUS (launched 23/04/2015), a sounding rocket experiment that contained a module to enable frequency stabilization of a DFB laser to the 87Rb D2 transition.
  • KALEXUS (launched 23/01/2016), a sounding rocket experiment that contained the first 39K spectroscopy in space.
  • MAIUS (launches 23/01/2017), a sounding rocket mission that created the first artificially created BEC in space, as well as a preparation of magnetic substates.
  • QUANTUS-I

Team Members

Currently working on QUANTUS missions are Jean-Pierre Marburger, Moritz Mihm, Peter Stromberger, André Wenzlawski, Sören Boles and Janka Söhn.

Project Partners

The QUANTUS (QUANTengase Unter Schwerelosigkeit) project is a DLR-funded joint collaboration between seven German universities (University of Mainz, University of Hanover, Humboldt-University of Berlin, University of Hamburg, University of Bremen, University of Ulm and the Technical University of Darmstadt), the Ferdinand-Braun Institute in Berlin and DLR research institutes in Oberpfaffenhofen, Brunswick and Bremen, aiming for the study of ultra-cold quantum gases in microgravity.

Funding

The MAIUS, KALEXUS, FOKUS and BECCAL projects are supported by the German Space Agency DLR with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) under grant number 50 WP 1433, 50 WM 1345, 50 WM 1238 and 50 WP 1703, respectively.