Some of the most sensitive and precise measurements to date are based on matterwave interferometry with freely falling atomic clouds. Examples include high-precision measurements of inertia 1 , gravity 2 and rotation 3 . In order to achieve these very high sensitivities, the interrogation time has to be very long and consequently the experimental apparatus has to be very tall, in some cases reaching ten or even one hundred meters 4, 5 . Cancelling gravitational acceleration, e.g. in atomtronic circuits 6, 7 and matterwave guides 8 , will result in compact devices having much extended interrogation times and thus much increased sensitivity both for fundamental and practical measurements. In this letter, we demonstrate extremely smooth and controllable matterwave guides by transporting Bose-Einstein condensates (BEC) over macroscopic distances: We use a novel neutral-atom accelerator ring to bring BECs to very high speeds (16x their velocity of sound) and transport them in a magnetic matterwave guide for 15 cm whilst fully preserving their internal coherence. The high angular momentum of more than 40000h per atom gives access to the higher Landau levels of quantum Hall states. The hypersonic velocities combined with our ability to control the potentials with pico-Kelvin precision open new perspectives in the study of superfluidity and give rise to new regimes of tunnelling and transport 9-11 . Coherent matterwave guides are expected to enable interaction times of several seconds in highly compact devices. These developments will result in portable guided-atom interferometers for applications such as inertial navigation and gravity mapping.

We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning the status of cold atom technologies, the prospective scientific and societal opportunities offered by their deployment in space, and the developments needed before cold atoms could be operated in space. The cold atom technologies discussed include atomic clocks, quantum gravimeters and accelerometers, and atom interferometers. Prospective applications include metrology, geodesy and measurement of terrestrial mass change due to, e.g., climate change, and fundamental science experiments such as tests of the equivalence principle, searches for dark matter, measurements of gravitational waves and tests of quantum mechanics. We review the current status of cold atom technologies and outline the requirements for their space qualification, including the development paths and the corresponding technical milestones, and identifying possible pathfinder missions to pave the way for missions to exploit the full potential of cold atoms in space. Finally, we present a first draft of a possible road-map for achieving these goals, that we propose for discussion by the interested cold atom, Earth Observation, fundamental physics and other prospective scientific user communities, together with the European Space Agency (ESA) and national space and research funding agencies.

This approach permits much finer adjustments of the beam direction and position when compared to other beam steering techniques of the same mechanical precision. This results in a much increased precision, accuracy and mechanical stability. A precision of better than 5 µrad and 5 µm is demonstrated, resulting in a resolution in coupling efficiency of 0.1%. Together with the added flexibility of an additional beam steering element, this allows a great simplification of the design of the fiber coupler, which normally is the most complex and sensitive element on an optical fiber breadboard. We demonstrate a fiber to fiber coupling efficiency of more than 89.8%, with a stability of 0.2% in a stable temperature environment and 2% fluctuations over a temperature range from 10°C to 40°C over a measurement time of 2 G. Drougakis et al.14 hours. Furthermore, we do not observe any non-reversible change in the coupling efficiency after performing a series of tests over large temperature variations. This technique finds direct application in proposed missions for quantum experiments in space [1, 2, 3], e.g. where laser beams are used to cool and manipulate atomic clouds. IntroductionActive optics play a rapidly increasing role in space instrumentation, for example in satellite systems that have started to use LIDAR [4,5,6,7], optical communication [8], and laser ranging [9,10].Space-based quantum technologies and atom clocks rely on an intricate manipulation of a number of ultra-stable laser sources leading to highly complex optical signal conditioning setups, which can be problematic for space missions. In some cases, this can be handled by in-fiber devices, more often, however, the requirements exceed what can be achieved in single mode waveguide devices and optical benches handling fiber to free-space to fiber coupling are required. Examples include cases where precise frequency shifting (acoustooptic modulators) or very high extinction ratios are needed, such as proposals for cold atom experiments in space [11,12]. Many components require single mode fiber to fiber coupling resulting in very stringent requirements in alignment and stability of the optical breadboard and its components. To meet these requirements, the PHARAO cold atom clock designed for space application [13] needed to incorporate active stabilization of many optical components like the mirrors used to inject light into fibers. For the LISA Pathfinder and LISA candidate systems [14,15] the optical components were attached to the breadboard using hydroxyl bonding to achieve high stability standards, albeit at the cost of extreme requirements on the manufacturing process. Another approach used in MAIUS1 mission using a combination of different types adhesives and complex moving parts to steer the beam with high precision [16,17].In this paper, we report on a novel optical beam steering technique (OBST) for fiber to free-space to fiber coupling breadboards. We achieve robust, ultrastable and yet extremely fine beam steering using simple optical elements, lik...