Cold-atom sources for the Matter-wave laser Interferometric Gravitation Antenna (MIGA)
Quentin Beaufils, Leonid A. Sidorenkov, Pierre Lebegue, Bertrand Venon, David Holleville, Laurent Volodimer, M. Lours, Joseph Junca, X. Zou, Andréa D Bertoldi, M. Prevedelli, Dylan O. Sabulsky, Philippe Bouyer, Arnaud Landragin, B. Canuel, Rémi Geiger
Abstract The Matter-wave laser Interferometric Gravitation Antenna (MIGA) is an underground instrument using cold-atom interferometry to perform precision measurements of gravity gradients and strains. Following its installation at the low noise underground laboratory LSBB in the South-East of France, it will serve as a prototype for gravitational wave detectors with a horizontal baseline of 150 meters. Three spatially separated cold-atom interferometers will be driven by two common counter-propagating lasers to perform a measurement of the gravity gradient along this baseline. This article presents the cold-atom sources of MIGA, focusing on the design choices, the realization of the systems, the performances and the integration within the MIGA instrument.
Abstract The Matter-wave laser Interferometric Gravitation Antenna (MIGA) is an underground instrument using cold-atom interferometry to perform precision measurements of gravity gradients and strains. Following its installation at the low noise underground laboratory LSBB in the South-East of France, it will serve as a prototype for gravitational wave detectors with a horizontal baseline of 150 meters. Three spatially separated cold-atom interferometers will be driven by two common counter-propagating lasers to perform a measurement of the gravity gradient along this baseline. This article presents the cold-atom sources of MIGA, focusing on the design choices, the realization of the systems, the performances and the integration within the MIGA instrument.
The Matter-wave laser Interferometric Gravitation Antenna (MIGA) is an underground instrument using cold-atom interferometry to perform precision measurements of gravity gradients and strains. Following its installation at the low noise underground laboratory LSBB in the South-East of France, it will serve as a prototype for gravitational wave detectors with a horizontal baseline of 150 meters. Three spatially separated cold-atom interferometers will be driven by two common counter-propagating lasers to perform a measurement of the gravity gradient along this baseline. This article presents the cold-atom sources of MIGA, focusing on the design choices, the realization of the systems, the performances and the integration within the MIGA instrument.
The remarkable success of atom coherent manipulation techniques has motivated competitive research and development in precision metrology. Matter-wave inertial sensors – accelerometers, gyrometers, gravimeters – based on these techniques are all at the forefront of their respective measurement classes. Atom inertial sensors provide nowadays about the best accelerometers and gravimeters and allow, for instance, to make the most precise monitoring of gravity. New concepts of matter-wave interferometry can also be used to study the low frequency variations of the strain tensor of space-time and gravitation. For instance, the MIGA instrument, which is currently built in the underground laboratory in Rustrel, France will allow the monitoring of the evolution of the gravitational field at unprecedented sensitivity, which will be exploited both for geophysical studies and for Gravitational Waves (GWs) observations. This present will present the status of this instrument.
Matter-wave inertial sensing relies on the capability of manipulating the coherent wave nature of matter to build an interferometer and accurately measure a phase difference. Since the massive particle associated to the matter wave senses inertial effects, the interferometer represents an accurate inertial probe. Atom interferometers have benefited from the outstanding developments of laser-cooling techniques and reached accuracies comparable to those of inertial sensors based on optical interferometry. Thanks to their long term stability, they offer a breakthrough advance in accelerometry, gyroscopy and gravimetry, for applications to inertial guidance, geoid determinations, geophysics and metrology. They are also excellent candidates for laboratory-based tests of general relativity that could compete with the current tests using astronomical or macroscopic bodies. For example, they may provide new answers to the question of whether the free fall acceleration of a particle is universal, i.e. independent of its internal composition and quantum properties. We report here the first operation of an airborne quantum inertial sensor. We highlight their promising applications to inertial navigation and Earth observation. We also describe the improvement of the quantum sensor sensitivity in weightlessness, and discuss the possibility to conduct airborne or spaceborne tests of the Universality of Free Fall with quantum objects. We finally describe a matter-wave laser based interferometric gravitational antenna (MIGA). This infrastructure will allow for measuring with unprecedented resolution variations of the Earths gravity and of the strain of space-time allowing for enhancing the capabilities of existing and future gravitational wave detectors.
Rb atoms - a typical atomic species for emerging quantum technologies. This device, a customized laser system from the Muquans company, is designed for use in the challenging operating environment of the Laboratoire Souterrain à Bas Bruit (LSBB) in France, where a new large scale atom interferometer is being constructed underground - the MIGA antenna. The mobile bench comprises four frequency-agile C-band Telecom diode lasers that are frequency doubled to 780 nm after passing through high-power fiber amplifiers. The first laser is frequency stabilized on a saturated absorption signal via lock-in amplification, which serves as an optical frequency reference for the other three lasers via optical phase-locked loops. Power and polarization stability are maintained through a series of custom, flexible micro-optic splitter/combiners that contain polarization optics, acousto-optic modulators, and shutters. Here, we show how the laser system is designed, showcasing qualities such as reliability, stability, remote control, and flexibility, while maintaining the qualities of laboratory equipment. We characterize the laser system by measuring the power, polarization, and frequency stability. We conclude with a demonstration using a cold atom source from the MIGA project and show that this laser system fulfills all requirements for the realization of the antenna.
A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving rest frame for the trapped atoms. While still in this moving-frame molasses, the laser frequencies are further detuned from the atomic resonance (while maintaining this relative frequency shift) to cool the atom cloud's temperature to 2 K or below, corresponding to an rms velocity of less than 2 cm/s. After launch, the cold atoms undergo further state and velocity selection to prepare for atom interferometry. The atom interferometers are then realized using laser-induced stimulated Raman transitions to perform the necessary manipulations of each atom, and the resulting interferometer phase is measured using laser-induced fluorescence for state-normalized detection. More than 20 laser beams with independent controls of frequency, phase, and intensity are required for this measurement sequence. This instrument can facilitate the study of Earth's gravitational field from surface and air vehicles, as well as from space by allowing gravity mapping from a low-cost, single spacecraft mission. In addition, the operation of atom interferometer-based instruments in space offers greater sensitivity than is possible in terrestrial instruments due to the much longer interrogation times available in the microgravity environment. A space-based quantum gravity gradiometer has the potential to achieve sensitivities similar to the GRACE mission at long spatial wavelengths, and will also have resolution similar to GOCE for measurement at shorter length scales.
Gravity gradiometers based on atom-wave interferometry hold the promise for increased sensitivity, and suitability for space applications. This capability will significantly advance our knowledge of solid Earth and the oceans, as well as other solar system planets and their moons. The quantum interferometer gravity gradiometer is based on atom-wave interferometry, and is intrinsically more sensitive than laser interferometers, because of the finite mass of the atom and the shorter de Broglie wavelengths associated with atom waves. Recent advances in laser cooling and trapping have made quantum interferometer applications practical. In this paper the principle of the operation of the quantum gravity gradiometer will first be described, together with the progress in its development to date. Estimates for the performance, and projections for the sensitivity will also be presented, together with potential applications to gravity science. Over the past few years advanced in laser cooling has brought about a significant progress towards realization of ultra-high sensitivity gravity gradiometers based on atom wave (matter wave) interferometry. These instruments represent a powerful potential for sensitive measurements of the components of the gravity gradient tensor from space to provide access to three-dimensional maps of geophysical structures deep below the surface. The exquisite sensitivity associated with atom-wave interferometry holds a great promise for new gravity mapping and monitoring capabilities - higher measurement sensitivity, finer spatial resolution, and, most importantly, temporal monitoring. This implies measurement opportunities for the Earth Observing System to develop comprehensive models for the understanding of the planetary inner structure and dynamics, changes in ice sheets and ocean currents, changes in underground water storage, and weather, earthquake, and volcano prediction capabilities. In this paper, we will review briefly the principles of the quantum gravity gradiometer and its advantages in the space environment. We will then describe our laboratory experiment and report some of the component development work towards a space-borne system. Gravity gradiometers based on atom interferometers are currently under development at the Jet propulsion Laboratory under NASA sponsorship.