Quantum gas mixtures and dual-species atom interferometry in space.

The capability to reach ultracold atomic temperatures in compact instruments has recently been extended into space1,2. Ultracold temperatures amplify quantum effects, whereas free fall allows further cooling and longer interactions time with gravity-the final force without a quantum description. On Earth, these devices have produced macroscopic quantum phenomena such as Bose-Einstein condensates (BECs), superfluidity, and strongly interacting quantum gases3. Terrestrial quantum sensors interfering the superposition of two ultracold atomic isotopes have tested the universality of free fall (UFF), a core tenet of Einstein's classical gravitational theory, at the 10-12 level4. In space, cooling the elements needed to explore the rich physics of strong interactions or perform quantum tests of the UFF has remained elusive. Here, using upgraded hardware of the multiuser Cold Atom Lab (CAL) instrument aboard the International Space Station (ISS), we report, to our knowledge, the first simultaneous production of a dual-species BEC in space (formed from 87Rb and 41K), observation of interspecies interactions, as well as the production of 39K ultracold gases. Operating a single laser at a 'magic wavelength' at which Rabi rates of simultaneously applied Bragg pulses are equal, we have further achieved the first spaceborne demonstration of simultaneous atom interferometry with two atomic species (87Rb and 41K). These results are an important step towards quantum tests of UFF in space and will allow scientists to investigate aspects of few-body physics, quantum chemistry and fundamental physics in new regimes without the perturbing asymmetry of gravity.

Observation of Bose-Einstein condensates in an Earth-orbiting research lab.

Quantum mechanics governs the microscopic world, where low mass and momentum reveal a natural wave-particle duality. Magnifying quantum behaviour to macroscopic scales is a major strength of the technique of cooling and trapping atomic gases, in which low momentum is engineered through extremely low temperatures. Advances in this field have achieved such precise control over atomic systems that gravity, often negligible when considering individual atoms, has emerged as a substantial obstacle. In particular, although weaker trapping fields would allow access to lower temperatures1,2, gravity empties atom traps that are too weak. Additionally, inertial sensors based on cold atoms could reach better sensitivities if the free-fall time of the atoms after release from the trap could be made longer3. Planetary orbit, specifically the condition of perpetual free-fall, offers to lift cold-atom studies beyond such terrestrial limitations. Here we report production of rubidium Bose-Einstein condensates (BECs) in an Earth-orbiting research laboratory, the Cold Atom Lab. We observe subnanokelvin BECs in weak trapping potentials with free-expansion times extending beyond one second, providing an initial demonstration of the advantages offered by a microgravity environment for cold-atom experiments and verifying the successful operation of this facility. With routine BEC production, continuing operations will support long-term investigations of trap topologies unique to microgravity4,5, atom-laser sources6, few-body physics7,8 and pathfinding techniques for atom-wave interferometry9-12.

Author Correction: Observation of Bose-Einstein condensates in an Earth-orbiting research lab.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Pathfinder experiments with atom interferometry in the Cold Atom Lab onboard the International Space Station.

Deployment of ultracold atom interferometers (AI) into space will capitalize on quantum advantages and the extended freefall of persistent microgravity to provide high-precision measurement capabilities for gravitational, Earth, and planetary sciences, and to enable searches for subtle forces signifying physics beyond General Relativity and the Standard Model. NASA's Cold Atom Lab (CAL) operates onboard the International Space Station as a multi-user facility for fundamental studies of ultracold atoms and to mature space-based quantum technologies. We report on pathfinding experiments utilizing ultracold 87Rb atoms in the CAL AI. A three-pulse Mach-Zehnder interferometer was studied to understand the influence of ISS vibrations. Additionally, Ramsey shear-wave interferometry was used to manifest interference patterns in a single run that were observable for over 150 ms free-expansion time. Finally, the CAL AI was used to remotely measure the Bragg laser photon recoil as a demonstration of the first quantum sensor using matter-wave interferometry in space.

A highly miniaturized vacuum package for a trapped ion atomic clock.

We report on the development of a highly miniaturized vacuum package for use in an atomic clock utilizing trapped ytterbium-171 ions. The vacuum package is approximately 1 cm(3) in size and contains a linear quadrupole RF Paul ion trap, miniature neutral Yb sources, and a non-evaporable getter pump. We describe the fabrication process for making the Yb sources and assembling the vacuum package. To prepare the vacuum package for ion trapping, it was evacuated, baked at a high temperature, and then back filled with a helium buffer gas. Once appropriate vacuum conditions were achieved in the package, it was sealed with a copper pinch-off and was subsequently pumped only by the non-evaporable getter. We demonstrated ion trapping in this vacuum package and the operation of an atomic clock, stabilizing a local oscillator to the 12.6 GHz hyperfine transition of (171)Y b(+). The fractional frequency stability of the clock was measured to be 2 × 10(-11)/τ(1/2).

Multistage two-dimensional magneto-optical trap as a compact cold atom beam source.

A compact cold atom beam source based on a multistage two-dimensional magneto-optical trap (MOT) has been demonstrated and characterized. The multiple-stage design greatly reduces the overall size of the source apparatus while providing a high flux of atoms. The cold atom beam was used to load a separate MOT in ultrahigh vacuum, and we obtained an actual trap loading rate of 1.5 x 109 atoms/s while using only 20 mW of total laser power for the source. The entire source apparatus, including optics, can fit into a 4 cm x 4 cm x 13 cm volume.