ELGAR—a European Laboratory for Gravitation and Atom-interferometric Research

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 B07DS 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 Reviewe

Cold atoms in space: community workshop summary and proposed road-map

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

Cold atoms in space: community workshop summary and proposed road-map

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.publishedVersio

Cold atoms in space: community workshop summary and proposed road-map

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

AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space

Abstract: We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement other planned searches for dark matter, and exploit synergies with other gravitational wave detectors. We give examples of the extended range of sensitivity to ultra-light dark matter offered by AEDGE, and how its gravitational-wave measurements could explore the assembly of super-massive black holes, first-order phase transitions in the early universe and cosmic strings. AEDGE will be based upon technologies now being developed for terrestrial experiments using cold atoms, and will benefit from the space experience obtained with, e.g., LISA and cold atom experiments in microgravity. KCL-PH-TH/2019-65, CERN-TH-2019-12

Atom gradiometry for future Gravitational Wave Detectors

Les ondes gravitationnelles nous permettent d’élargir notre connaissance de l’univers en transportant sur de très grandes distances les informations reliées aux variations de masses. La détection de ces ondes est de première importante non seulement pour la physique fondamentale mais également pour les aspects technologiques des mesures de haute précision. Différents observatoires d’ondes gravitationnelles sont en opération ou en construction à travers le monde, avec des bandes de détection allant de 10^-9 Hz to 10^4 Hz.L’expérience MIGA (Matter Wave Interferometer Gravitational Antenna) a pour but de construire un réseau de gradiomètres atomiques en cavité sur une longueur de base de 150 m au laboratoire Souterrain Bas Bruit (LSBB). En comparaison avec les détecteurs optiques de type Michelson en cavité, les gradiomètre atomiques ouvrent la voie vers une détection en dessous du Hz, et peuvent permettre une détection dans une gamme de fréquence 0.1 Hz - 10 Hz complémentaire par rapport aux instruments existants ou en construction.Dans ce cadre, le LP2N réalise une expérience de démonstration consistant en un gradiomètre atomique en cavité basé sur deux sources d’atomes froids de Rb. Nous discutons dans cette thèse les progrès réalisés sur cette expérience. En particulier, la réalisation et le commissioning du système à vide ainsi que la caractérisation complète d’une des sources atomiques.Dans ce manuscrit, nous rapportons également les travaux théoriques réalisés dans un second volet de cette thèse et consistant à l’étude du couplage optimal entre un interféromètre atomique et une cavité optique pour la détection des ondes gravitationnelles. Nous présentons ainsi une géométrie originale de détection permettant d’obtenir une amplification du signal d’onde gravitationnel détecté par un interféromètre atomique.Gravitational waves expand our observation scope of the universe, carrying information through time and space undisturbed due to their inability to be scattered or absorbed. The detection of gravitational waves is of great significance to the progress of fundamental physics research and associated experimental technology. Gravitational-wave observatories are in operation or under construction worldwide, with detection frequencies ranging from 10^-9 Hz to 10^4 Hz.The Matter Wave Interferometer Gravitational Antenna (MIGA) experiment aims to build an atomic gradiometer consisting of one 150 m long optical cavities on the LSBB platform based on the increasingly mature atomic interference technology. Compared with optical interferometers, atom gradiometers can reduce noise in the low-frequency range, filling a gap in gravitational wave detection in the band 0.1 Hz - 10 Hz.At LP2N, as a demonstration experiment for gravitational wave antennas, an atom interferometer based on quasi-Bragg scattering and marginally-stable cavity has been built. We are currently building a 6.35 m atom gradiometer composed of two atom sources and made the first attempt to observe an interference signal. We discuss the implementation of this atom gradiometer, focusing on our achieved vacuum of 1.4x10^-9 mbar in an enormous vacuum chamber as well as the completed tuning of the first atomic source.This thesis elucidates the difference between an atom gradiometer and an optical interferometer for gravitational wave detection. We propose a nested three-cavity system through two orthogonal optical cavities - a structure that can improve the strain sensitivity of atom interferometry, allowing it to exceed the standard quantum limit

Gradiométrie atomique pour les futurs détecteurs d'ondes gravitationnelles

Gravitational waves expand our observation scope of the universe, carrying information through time and space undisturbed due to their inability to be scattered or absorbed. The detection of gravitational waves is of great significance to the progress of fundamental physics research and associated experimental technology. Gravitational-wave observatories are in operation or under construction worldwide, with detection frequencies ranging from 10^-9 Hz to 10^4 Hz.The Matter Wave Interferometer Gravitational Antenna (MIGA) experiment aims to build an atomic gradiometer consisting of one 150 m long optical cavities on the LSBB platform based on the increasingly mature atomic interference technology. Compared with optical interferometers, atom gradiometers can reduce noise in the low-frequency range, filling a gap in gravitational wave detection in the band 0.1 Hz - 10 Hz.At LP2N, as a demonstration experiment for gravitational wave antennas, an atom interferometer based on quasi-Bragg scattering and marginally-stable cavity has been built. We are currently building a 6.35 m atom gradiometer composed of two atom sources and made the first attempt to observe an interference signal. We discuss the implementation of this atom gradiometer, focusing on our achieved vacuum of 1.4x10^-9 mbar in an enormous vacuum chamber as well as the completed tuning of the first atomic source.This thesis elucidates the difference between an atom gradiometer and an optical interferometer for gravitational wave detection. We propose a nested three-cavity system through two orthogonal optical cavities - a structure that can improve the strain sensitivity of atom interferometry, allowing it to exceed the standard quantum limit.Les ondes gravitationnelles nous permettent d’élargir notre connaissance de l’univers en transportant sur de très grandes distances les informations reliées aux variations de masses. La détection de ces ondes est de première importante non seulement pour la physique fondamentale mais également pour les aspects technologiques des mesures de haute précision. Différents observatoires d’ondes gravitationnelles sont en opération ou en construction à travers le monde, avec des bandes de détection allant de 10^-9 Hz to 10^4 Hz.L’expérience MIGA (Matter Wave Interferometer Gravitational Antenna) a pour but de construire un réseau de gradiomètres atomiques en cavité sur une longueur de base de 150 m au laboratoire Souterrain Bas Bruit (LSBB). En comparaison avec les détecteurs optiques de type Michelson en cavité, les gradiomètre atomiques ouvrent la voie vers une détection en dessous du Hz, et peuvent permettre une détection dans une gamme de fréquence 0.1 Hz - 10 Hz complémentaire par rapport aux instruments existants ou en construction.Dans ce cadre, le LP2N réalise une expérience de démonstration consistant en un gradiomètre atomique en cavité basé sur deux sources d’atomes froids de Rb. Nous discutons dans cette thèse les progrès réalisés sur cette expérience. En particulier, la réalisation et le commissioning du système à vide ainsi que la caractérisation complète d’une des sources atomiques.Dans ce manuscrit, nous rapportons également les travaux théoriques réalisés dans un second volet de cette thèse et consistant à l’étude du couplage optimal entre un interféromètre atomique et une cavité optique pour la détection des ondes gravitationnelles. Nous présentons ainsi une géométrie originale de détection permettant d’obtenir une amplification du signal d’onde gravitationnel détecté par un interféromètre atomique

Atom gradiometry for future Gravitational Wave Detectors

Les ondes gravitationnelles nous permettent d’élargir notre connaissance de l’univers en transportant sur de très grandes distances les informations reliées aux variations de masses. La détection de ces ondes est de première importante non seulement pour la physique fondamentale mais également pour les aspects technologiques des mesures de haute précision. Différents observatoires d’ondes gravitationnelles sont en opération ou en construction à travers le monde, avec des bandes de détection allant de 10^-9 Hz to 10^4 Hz.L’expérience MIGA (Matter Wave Interferometer Gravitational Antenna) a pour but de construire un réseau de gradiomètres atomiques en cavité sur une longueur de base de 150 m au laboratoire Souterrain Bas Bruit (LSBB). En comparaison avec les détecteurs optiques de type Michelson en cavité, les gradiomètre atomiques ouvrent la voie vers une détection en dessous du Hz, et peuvent permettre une détection dans une gamme de fréquence 0.1 Hz - 10 Hz complémentaire par rapport aux instruments existants ou en construction.Dans ce cadre, le LP2N réalise une expérience de démonstration consistant en un gradiomètre atomique en cavité basé sur deux sources d’atomes froids de Rb. Nous discutons dans cette thèse les progrès réalisés sur cette expérience. En particulier, la réalisation et le commissioning du système à vide ainsi que la caractérisation complète d’une des sources atomiques.Dans ce manuscrit, nous rapportons également les travaux théoriques réalisés dans un second volet de cette thèse et consistant à l’étude du couplage optimal entre un interféromètre atomique et une cavité optique pour la détection des ondes gravitationnelles. Nous présentons ainsi une géométrie originale de détection permettant d’obtenir une amplification du signal d’onde gravitationnel détecté par un interféromètre atomique.Gravitational waves expand our observation scope of the universe, carrying information through time and space undisturbed due to their inability to be scattered or absorbed. The detection of gravitational waves is of great significance to the progress of fundamental physics research and associated experimental technology. Gravitational-wave observatories are in operation or under construction worldwide, with detection frequencies ranging from 10^-9 Hz to 10^4 Hz.The Matter Wave Interferometer Gravitational Antenna (MIGA) experiment aims to build an atomic gradiometer consisting of one 150 m long optical cavities on the LSBB platform based on the increasingly mature atomic interference technology. Compared with optical interferometers, atom gradiometers can reduce noise in the low-frequency range, filling a gap in gravitational wave detection in the band 0.1 Hz - 10 Hz.At LP2N, as a demonstration experiment for gravitational wave antennas, an atom interferometer based on quasi-Bragg scattering and marginally-stable cavity has been built. We are currently building a 6.35 m atom gradiometer composed of two atom sources and made the first attempt to observe an interference signal. We discuss the implementation of this atom gradiometer, focusing on our achieved vacuum of 1.4x10^-9 mbar in an enormous vacuum chamber as well as the completed tuning of the first atomic source.This thesis elucidates the difference between an atom gradiometer and an optical interferometer for gravitational wave detection. We propose a nested three-cavity system through two orthogonal optical cavities - a structure that can improve the strain sensitivity of atom interferometry, allowing it to exceed the standard quantum limit

Gradiométrie atomique pour les futurs détecteurs d'ondes gravitationnelles

Gravitational waves expand our observation scope of the universe, carrying information through time and space undisturbed due to their inability to be scattered or absorbed. The detection of gravitational waves is of great significance to the progress of fundamental physics research and associated experimental technology. Gravitational-wave observatories are in operation or under construction worldwide, with detection frequencies ranging from 10^-9 Hz to 10^4 Hz.The Matter Wave Interferometer Gravitational Antenna (MIGA) experiment aims to build an atomic gradiometer consisting of one 150 m long optical cavities on the LSBB platform based on the increasingly mature atomic interference technology. Compared with optical interferometers, atom gradiometers can reduce noise in the low-frequency range, filling a gap in gravitational wave detection in the band 0.1 Hz - 10 Hz.At LP2N, as a demonstration experiment for gravitational wave antennas, an atom interferometer based on quasi-Bragg scattering and marginally-stable cavity has been built. We are currently building a 6.35 m atom gradiometer composed of two atom sources and made the first attempt to observe an interference signal. We discuss the implementation of this atom gradiometer, focusing on our achieved vacuum of 1.4x10^-9 mbar in an enormous vacuum chamber as well as the completed tuning of the first atomic source.This thesis elucidates the difference between an atom gradiometer and an optical interferometer for gravitational wave detection. We propose a nested three-cavity system through two orthogonal optical cavities - a structure that can improve the strain sensitivity of atom interferometry, allowing it to exceed the standard quantum limit.Les ondes gravitationnelles nous permettent d’élargir notre connaissance de l’univers en transportant sur de très grandes distances les informations reliées aux variations de masses. La détection de ces ondes est de première importante non seulement pour la physique fondamentale mais également pour les aspects technologiques des mesures de haute précision. Différents observatoires d’ondes gravitationnelles sont en opération ou en construction à travers le monde, avec des bandes de détection allant de 10^-9 Hz to 10^4 Hz.L’expérience MIGA (Matter Wave Interferometer Gravitational Antenna) a pour but de construire un réseau de gradiomètres atomiques en cavité sur une longueur de base de 150 m au laboratoire Souterrain Bas Bruit (LSBB). En comparaison avec les détecteurs optiques de type Michelson en cavité, les gradiomètre atomiques ouvrent la voie vers une détection en dessous du Hz, et peuvent permettre une détection dans une gamme de fréquence 0.1 Hz - 10 Hz complémentaire par rapport aux instruments existants ou en construction.Dans ce cadre, le LP2N réalise une expérience de démonstration consistant en un gradiomètre atomique en cavité basé sur deux sources d’atomes froids de Rb. Nous discutons dans cette thèse les progrès réalisés sur cette expérience. En particulier, la réalisation et le commissioning du système à vide ainsi que la caractérisation complète d’une des sources atomiques.Dans ce manuscrit, nous rapportons également les travaux théoriques réalisés dans un second volet de cette thèse et consistant à l’étude du couplage optimal entre un interféromètre atomique et une cavité optique pour la détection des ondes gravitationnelles. Nous présentons ainsi une géométrie originale de détection permettant d’obtenir une amplification du signal d’onde gravitationnel détecté par un interféromètre atomique