AEDGE: Atomic experiment for dark matter and gravity exploration in space

Experimental Astronomy https://doi.org/10.1007/s10686-021-09701-3 ORIGINAL ARTICLE AEDGE: Atomic experiment for dark matter and gravity exploration in space Andrea Bertoldi1 · Kai Bongs2 · Philippe Bouyer1 · Oliver Buchmueller3 · Benjamin Canuel1 · Laurentiu-Ioan Caramete4 · Maria Luisa Chiofalo5 · Jonathon Coleman6 · Albert De Roeck7,8 · John Ellis9,10,11 · Peter W. Graham12 · Martin G. Haehnelt13 · Aurélien Hees14 · Jason Hogan12 · Wolf von Klitzing15 · Markus Krutzik16 · Marek Lewicki9,17 · Christopher McCabe9 · Achim Peters16 · Ernst Rasel18 · Albert Roura19 · Dylan Sabulsky1 · Stephan Schiller20 · Christian Schubert18 · Carla Signorini5 · Fiodor Sorrentino21 · Yeshpal Singh2 · Guglielmo Maria Tino22,23 · Ville Vaskonen9,10 · Ming-Sheng Zhan24 Received: 3 December 2020 / Accepted: 27 January 2021 / © The Author(s) 2021 Abstract This article contains a summary of the White Paper submitted in 2019 to the ESA Voyage 2050 process, which was subsequently published in EPJ Quantum Technology (AEDGE Collaboration et al. EPJ Quant. Technol. 7,6 2020). We propose in this White Paper a concept for a space experiment using cold atoms to search for ultralight 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. Keywords Dark matter · Dark energy · Gravitational waves · Quantum technology  Oliver Buchmueller Extended author information available on the last page of the article. Experimental Astronomy 1 Preface This article contains a summary of the White Paper submitted in 2019 by the same authors to the ESA Voyage 2050 process, and also mentions a few subsequent scientific and technical developments. The paper was published in EPJ Quantum Technology [1], where we have welcomed as supporting authors participants in the Workshop on Atomic Experiments for Dark Matter and Gravity Exploration held at CERN [2], as well as other interested scientists. 2 Science case Two of the most important issues in fundamental physics, astrophysics and cosmology are the nature of dark matter (DM) and the exploration of the gravitational wave (GW) spectrum. Multiple observations from the dynamics of galaxies and clusters to the spectrum of the cosmological microwave background (CMB) radiation measured by ESA’s Planck satellite and other [3] experiments indicate that there is far more DM than conventional matter in the Universe, but its physical composition remains a complete mystery. The two most popular classes of DM scenario invoke either coherent waves of ultra-light bosonic fields, or weakly-interacting massive particles (WIMPs). In the absence so far of any positive indications for WIMPs from accelerator and other laboratory experiments, there is increasing interest in ultra-light bosonic candidates, many of which appear in theories that address other problems in fundamental physics. Such bosons are among the priority targets for AEDGE. The discovery of GWs by the LIGO [4] and Virgo [5] laser interferometer experiments has opened a new window on the Universe, through which waves over a wide range of frequencies can provide new information about high-energy astrophysics and cosmology. Just as astronomical observations at different wavelengths provide complementary information about electromagnetic sources, measurements of GWs in different frequency bands are complementary and synergistic. In addition to the ongoing LIGO and Virgo experiments at relatively high frequencies  10 Hz, which will soon be joined by the KAGRA [6] detector in Japan and the INDIGO project [7] to build a LIGO detector in India, with the Einstein Telescope (ET) [8, 9] and Cosmic Explorer (CE) [10] experiments being planned for similar frequency ranges, ESA has approved for launch before the period being considered for Voyage 2050 missions the LISA mission, which will be most sensitive at frequencies  10−1 Hz, and the Taiji [11] and TianQin [12] missions proposed in China will have similar sensitivity to LISA. AEDGE is optimized for the mid-frequency range between LISA/Taiji/TianQin and LIGO/Virgo/KAGRA/INDIGO/ET/CE 1 . This range is ideal for probing the formation of the super-massive black holes known to be present in 1 The ALIA proposal in Europe [13] and the DECIGO proposal in Japan [14] have been aimed at a similar frequency range, and the scientific interest of this frequency range has recently been stressed in [15, 16] and [17]. Experimental Astronomy many galaxies. Also, AEDGE’s observations of astrophysical sources will complement those by other GW experiments at lower and higher frequencies, completing sets of measurements from inspiral to merger and ringdown, yielding important synergies as we illustrate below. GWs are the other priority targets for AEDGE. In addition to these primary scientific objectives, several other potential objectives for cold atom experiments in space are under study. These may include constraining possible variations in fundamental constants, probing dark energy, and probing basic physical principles such as Lorentz invariance and quantum mechanics. Cold quantum gases provide powerful technologies that are already mature for the AEDGE goals, while also developing rapidly [18]. The developments of these technologies can be expected to offer AEDGE more possibilities on the Voyage 2050 time scale. AEDGE is a uniquely interdiscplinary and versatile mission. 3 Experimental considerations The design of AEDGE requires two satellites operating along a single line-of-sight and separated by a long distance. The payload of each satellite will consist of cold atom technology as developed for state-of-the-art atom interferometry and atomic clocks. As two satellites are needed to accomplish its science goals, the AEDGE mission planning costs are estimated to be in the range of an L-class mission. However, in view of the international interest in the AEDGE science goals, the possibility of international cooperation and co-funding of the mission may be investigated. There are several cold atom projects based on various technologies that are currently under construction, planned or proposed, which address the principal technical challenges and could be considered i (...truncated)