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Quantensensoren basierend auf Materiewelleninterferometrie können zur Vermessung einer Vielzahl verschiedenster physikalischer Größen verwendet werden. Die Anwendung reicht von der präzisen Bestimmung fundamentaler Naturkonstanten bis zur Vermessung inertialer Kräfte wie Beschleunigungen und Rotationen. Hiermit lassen sich bspw. quantenbasierte Inertialsensoren für Navigationsaufgaben, Gravimeter oder auch Gradiometer realisieren. Hierzu sind ultrakalte oder kondensierte atomare Ensembles notwendig, da die Sensitivität des Materiewelleninterferometers mit der Dauer des Interferometers skaliert. Im Rahmen dieser Arbeit wurde untersucht, inwiefern sich die Expansionseigenschaften eines Quantengases manipulieren lassen um die Detektierbarkeit auch nach Freifallzeiten von mehreren Sekunden zu gewahrleisten. Hierzu wurde eine kompakte und robuste Quelle quantenentarteter Gase in der Mikrogravitationsumgebung des Fallturm Bremen genutzt. Mit ihr lassen sich Bose-Einstein Kondensate aus 100.000 Rb-87 Atomen mit einer Repetitionsrate von 1 Hz und einer internen kinetischen Energie von 2 nK erzeugen. Eine kollektive Größenoszillation wird mit einer magnetischen Linse kombiniert um ein Materiewellenlinsensystem zu formen. Die Messkampagnen im Fallturm wurden von Simulationen begleitet, um quantitative Aussagen zu den Expansionseigenschaften und der Detektierbarkeit des Ensembles zu treffen. Es konnte gezeigt werden, dass sich die interne kinetische Energie eines Bose-Einstein Kondensates mithilfe des Materiewellenlinsensystems auf 38 pK reduzieren lässt. Ein derart manipuliertes atomares Ensemble konnte noch nach einer Freifallzeit von 2 s detektiert werden. Durch Extrapolation der Simulationsergebnisse konnte abgeschätzt werden, dass die Detektierbarkeit für bis zu 17 s gegeben wäre. Dies stellt einen herausragenden Eingangszustand fur künftige, vor allem weltraumgestützte Quantensensoren dar., Quantum-sensors based on matter-wave interferometrie can be used for measuring a multitude of different physical properties. The application ranges from the precise determination of fundamental natural constants to the measurement of inertial forces such as acceleration and rotation. This can be used to implement e. g. quantum-based inertial sensors for navigation tasks, gravimeters or gradiometers. For this, ultracold or condensed atomic ensembles are necessary, since the sensitivity of the matter-wave interferometer scales with the duration of the interferometer. In the context of this work, it was investigated to what extent the expansion properties of a quantum gas can be manipulated in order to ensure detectability even after free-fall times of several seconds. For this purpose, a compact and robust source of quantum degenerate gases in the microgravity environment of the Bremen drop tower was used [1–4]. It can be used to generate Bose-Einstein condensates of 100 000 87Rb atoms with a repetition rate of 1 Hz and an internal kinetic energy of 2 nK [4, 5]. A collective-mode excitation is combined with a magnetic lens to form a time-domain matter-wave lens system. The measurements in the drop tower were accompanied by simulations in order to make quantitative statements about the expansion properties and the ensembles detectability. It was shown that the internal kinetic energy of a Bose- Einstein condensate could be reduced to 38 pK using the matter-wave lens-system. An atomic ensemble manipulated in this way could still be detected after a free fall time of 2 s. By extrapolating the results of the simulations, it could be estimated that the detectability would be given for up to 17 s. This represents an outstanding initial state for future, especially space-based quantum sensors as proposed in STE-QUEST [6] or currently realized in BECCAL

Gravitational waves (GWs) were observed for the first time in 2015, one century after Einstein predicted their existence. There is now growing interest to extend the detection bandwidth to low frequency. The scientific potential of multi-frequency GW astronomy is enormous as it would enable to obtain a more complete picture of cosmic events and mechanisms. This is a unique and entirely new opportunity for the future of astronomy, the success of which depends upon the decisions being made on existing and new infrastructures. The prospect of combining observations from the future space-based instrument LISA together with third generation ground based detectors will open the way toward multi-band GW astronomy, but will leave the infrasound (0.1–10 Hz) band uncovered. GW detectors based on matter wave interferometry promise to fill such a sensitivity gap. We propose the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an underground infrastructure based on the latest progress in atomic physics, to study space–time and gravitation with the primary goal of detecting GWs in the infrasound band. ELGAR will directly inherit from large research facilities now being built in Europe for the study of large scale atom interferometry and will drive new pan-European synergies from top research centers developing quantum sensors. ELGAR will measure GW radiation in the infrasound band with a peak strain sensitivity of 3.3 x 10 [hoch]-20 / [Wurzel] Hz at 1.7 Hz. The antenna will have an impact on diverse fundamental and applied research fields beyond GW astronomy, including gravitation, general relativity, and geology.

Gravitational waves (GWs) were observed for the first time in 2015, one century after Einstein predicted their existence. There is now growing interest to extend the detection bandwidth to low frequency. The scientific potential of multi-frequency GW astronomy is enormous as it would enable to obtain a more complete picture of cosmic events and mechanisms. This is a unique and entirely new opportunity for the future of astronomy, the success of which depends upon the decisions being made on existing and new infrastructures. The prospect of combining observations from the future space-based instrument LISA together with third generation ground based detectors will open the way toward multi-band GW astronomy, but will leave the infrasound (0.1–10 Hz) band uncovered. GW detectors based on matter wave interferometry promise to fill such a sensitivity gap. We propose the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an underground infrastructure based on the latest progress in atomic physics, to study space–time and gravitation with the primary goal of detecting GWs in the infrasound band. ELGAR will directly inherit from large research facilities now being built in Europe for the study of large scale atom interferometry and will drive new pan-European synergies from top research centers developing quantum sensors. ELGAR will measure GW radiation in the infrasound band with a peak strain sensitivity of $3.3{\times}1{0}^{-22}/\sqrt{\text{Hz}}$ at 1.7 Hz. The antenna will have an impact on diverse fundamental and applied research fields beyond GW astronomy, including gravitation, general relativity, and geology., AB acknowledges support from the ANR (project EOSBECMR), IdEx Bordeaux—LAPHIA (project OE-TWR), theQuantERA ERA-NET (project TAIOL) and the Aquitaine Region (projets IASIG3D and USOFF)., XZ thanks the China Scholarships Council (No. 201806010364) program for financial support. JJ thanks ‘AssociationNationale de la Recherche et de la Technologie’ for financial support (No. 2018/1565)., SvAb, NG, SL, EMR, DS, and CS gratefully acknowledge support by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under Grants No. DLR∼50WM1641 (PRIMUS-III), 50WM1952 (QUANTUS-V-Fallturm), and 50WP1700 (BECCAL), 50WM1861 (CAL), 50WM2060 (CARIOQA) as well as 50RK1957 (QGYRO), SvAb, NG, SL, EMR, DS, and CS gratefully acknowledge support by ‘Niedersächsisches Vorab’ through the ‘Quantum- and Nano-Metrology (QUANOMET)’ initiative within the project QT3, and through ‘Förderung von Wissenschaft und Technik in Forschung und Lehre’ for the initial funding of research in the new DLR-SI Institute, the CRC 1227 DQ-mat within the projects A05 and B07, DS gratefully acknowledges funding by the Federal Ministry of Education and Research (BMBF) through the funding program Photonics Research Germany under contract number 13N14875., RG acknowledges Ville de Paris (Emergence programme HSENS-MWGRAV), ANR (project PIMAI) and the Fundamental Physics and Gravitational Waves (PhyFOG) programme of Observatoire de Paris for support. We also acknowledge networking support by the COST actions GWverse CA16104 and AtomQT CA16221 (Horizon 2020 Framework Programme of the European Union)., The work was also supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under Grant Nos.∼50WM1556, 50WM1956 and 50WP1706 as well as through the DLR Institutes DLR-SI and DLR-QT., PA-S, MN, and CFS acknowledge support from contracts ESP2015-67234-P and ESP2017-90084-P from the Ministry of Economy and Business of Spain (MINECO), and from contract 2017-SGR-1469 from AGAUR (Catalan government)., SvAb, NG, SL, EMR, DS, and CS gratefully acknowledge support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy—EXC-2123 QuantumFrontiers—390837967 (B2) andCRC1227 ‘DQ-mat’ within projects A05, B07 and B09., LAS thanks Sorbonne Universités (Emergence project LORINVACC) and Conseil Scientifique de l'Observatoire de Paris for funding., This work was realized with the financial support of the French State through the ‘Agence Nationale de la Recherche’ (ANR) in the frame of the ‘MRSEI’ program (Pre-ELGAR ANR-17-MRS5-0004-01) and the ‘Investissement d'Avenir’ program (Equipex MIGA: ANR-11-EQPX-0028, IdEx Bordeaux—LAPHIA: ANR-10-IDEX-03-02)., Peer Reviewed

Gravitational waves (GWs) were observed for the first time in 2015, one century after Einstein predicted their existence. There is now growing interest to extend the detection bandwidth to low frequency. The scientific potential of multi-frequency GW astronomy is enormous as it would enable to obtain a more complete picture of cosmic events and mechanisms. This is a unique and entirely new opportunity for the future of astronomy, the success of which depends upon the decisions being made on existing and new infrastructures. The prospect of combining observations from the future space-based instrument LISA together with third generation ground based detectors will open the way toward multi-band GW astronomy, but will leave the infrasound (0.1-10 Hz) band uncovered. GW detectors based on matter wave interferometry promise to fill such a sensitivity gap. We propose the European Laboratory for Gravitation and Atom-interferometric Research (ELGAR), an underground infrastructure based on the latest progress in atomic physics, to study space-time and gravitation with the primary goal of detecting GWs in the infrasound band. ELGAR will directly inherit from large research facilities now being built in Europe for the study of large scale atom interferometry and will drive new pan-European synergies from top research centers developing quantum sensors. ELGAR will measure GW radiation in the infrasound band with a peak strain sensitivity of 3.3 × 10-22/√Hz at 1.7 Hz. The antenna will have an impact on diverse fundamental and applied research fields beyond GW astronomy, including gravitation, general relativity, and geology.

Quantum sensors based on coherent matter-waves are precise measurement devices whose ultimate accuracy is achieved with Bose-Einstein condensates (BECs) in extended free fall. This is ideally realized in microgravity environments such as drop towers, ballistic rockets and space platforms. However, the transition from lab-based BEC machines to robust and mobile sources with comparable performance is a challenging endeavor. Here we report on the realization of a miniaturized setup, generating a flux of 4x10(5) quantum degenerate Rb-87 atoms every 1.6 s. Ensembles of 1 x 10(5) atoms can be produced at a 1 Hz rate. This is achieved by loading a cold atomic beam directly into a multi-layer atom chip that is designed for efficient transfer from laser-cooled to magnetically trapped clouds. The attained flux of degenerate atoms is on par with current lab-based BEC experiments while offering significantly higher repetition rates. Additionally, the flux is approaching those of current interferometers employing Raman-type velocity selection of laser-cooled atoms. The compact and robust design allows for mobile operation in a variety of demanding environments and paves the way for transportable high-precision quantum sensors.