AION: An Atom Interferometer Observatory and Network (1911.11755v3)

Abstract: We outline the experimental concept and key scientific capabilities of AION (Atom Interferometer Observatory and Network), a proposed UK-based experimental programme using cold strontium atoms to search for ultra-light dark matter, to explore gravitational waves in the mid-frequency range between the peak sensitivities of the LISA and LIGO/Virgo/ KAGRA/INDIGO/Einstein Telescope/Cosmic Explorer experiments, and to probe other frontiers in fundamental physics. AION would complement other planned searches for dark matter, as well as probe mergers involving intermediate mass black holes and explore early universe cosmology. AION would share many technical features with the MAGIS experimental programme in the US, and synergies would flow from operating AION in a network with this experiment, as well as with other atom interferometer experiments such as MIGA, ZAIGA and ELGAR. Operating AION in a network with other gravitational wave detectors such as LIGO, Virgo and LISA would also offer many synergies.

• The paper introduces a novel atom interferometer network using cold strontium atoms to explore ultra-light dark matter and gravitational waves in a previously uncharted frequency band.
• The paper details a multi-stage experimental design that scales from 10-meter setups to kilometer-scale observatories, employing large momentum transfer techniques to boost sensitivity.
• The paper highlights potential breakthroughs in testing fundamental physics principles and deepening our understanding of particle physics, astrophysics, and cosmology.

AION: Advancements in Atom Interferometry for Physics Exploration

The paper "AION: An Atom Interferometer Observatory and Network" details a proposal for an advanced observational program using atom interferometry centered around cold strontium atoms. This proposed initiative aims to explore several fundamental physics domains, including the search for ultra-light dark matter and the detection of gravitational waves in the mid-frequency range, a crucial band currently not fully covered by existing gravitational wave detectors like LIGO, Virgo, and LISA. The AION program seeks to provide a comprehensive platform for interdisciplinary exploration, enhancing understanding in particle physics, astrophysics, and cosmology.

Scientific Objectives

One of the primary ambitions of AION is to expand the search for ultra-light dark matter candidates, such as dilatons, relaxions, moduli, axions, and vector bosons, which exist beyond the Standard Model. AION aims to cover a mass range from approximately $10^{-12}$ to $10^{-17}$ eV, offering an unprecedented sensitivity level that current and planned experiments are yet to achieve. The synergy obtained through networking with experiments like MAGIS, MIGA, ZAIGA, and ELGAR is anticipated to further enhance detection capabilities, especially for events distributed in a wide geographical area.

Another significant research frontier is the exploration of gravitational waves (GWs) in the mid-frequency range ($0.01$ Hz to a few Hz), a window between the operational bandwidths of LISA and LIGO/Virgo. This frequency range is relatively uncontaminated by astrophysical foreground noise like that from white dwarfs, enabling clearer detection of GWs from intermediate-mass black hole mergers, first-order phase transitions in the early universe, and potentially cosmic strings. By constructing a staged series of atom interferometers, increasing in baseline length from 10 meters to kilometer-scale, AION will enable detailed measurement of these phenomena, bridging existing gaps in the sensitivity spectrum of GW detectors.

Technological Framework

AION leverages atom interferometry, a technique that encompasses deploying numerous atom interferometers in differential phase measurements to detect GWs and dark matter. These devices use single-photon transitions between atomic states due to their reduced noise interference capability compared to two-photon transitions, which is crucial in extending detector baseline while maintaining sensitivity. The use of strontium atoms is particularly advantageous given their favorable transitions for laser cooling and long-lived metastable states suitable for high-precision measurements.

Large momentum transfer (LMT) techniques will be employed to amplify interferometric signals, an approach validated by recent demonstrations achieving $141 \hbar k$ LMT. The systematic operation of these atom interferometers requires finely controlled pulse sequences in resonant or broadband modes to maximize their sensitivity to GWs and dark matter signals. Sensitivity projections are calculated based on achievable parameters set for each AION stage, from the initial 10-meter setup to the ambitious kilometer-scale and satellite-based observatories.

Implications and Future Prospects

The AION program promises a comprehensive contribution to the global understanding of dark matter and gravitational phenomena. With the potential for high spatial resolution measurements and early detection of GW events, AION positions itself as an essential component in the network of next-generation observatories. It could offer insights into the nature of dark matter, provide predictive capabilities for GW events, and enable novel tests of fundamental physical principles like the equivalence principle, Lorentz invariance, and possibly reveal new forces.

The successful deployment and operation of AION’s stages could ultimately result in transformative advancements in observational physics, opening new investigative paths across varied scales of the universe. Future prospects include integrating AION with other major initiatives to enhance precision cosmology and high-energy physics research, firmly establishing it as a pivotal platform in the landscape of scientific exploration.