Studies of general relativity with quantum sensors
G. Lefèvre, G. Condon, Isabelle Riou, Laure Chichet, M. Essayeh, Martin Rabault, Laura Antoni‐Micollier, N. Mielec, David Holleville, Louis Amand, Rémi Geiger, Arnaud Landragin, M. Prevedelli, B. Barrett, Baptiste Battelier, Andréa D Bertoldi, B. Canuel, Philippe Bouyer
We present two projects aiming to probe key aspects of the theory of General Relativity with high-precision quantum sensors. These projects use cold-atom interferometry with the aim of measuring gravitational waves and testing the equivalence principle. To detect gravitational waves, a large multi-sensor demonstrator is currently under construction that will exploit correlations between three atom interferometers spread along a 200 m optical cavity. Similarly, a test of the weak equivalence principle is currently underway using a compact and mobile dual-species interferometer, which will serve as a prototype for future high-precision tests onboard an orbiting satellite. We present recent results and improvements related to both projects.
We present two projects aiming to probe key aspects of the theory of General Relativity with high-precision quantum sensors. These projects use cold-atom interferometry with the aim of measuring gravitational waves and testing the equivalence principle. To detect gravitational waves, a large multi-sensor demonstrator is currently under construction that will exploit correlations between three atom interferometers spread along a 200 m optical cavity. Similarly, a test of the weak equivalence principle is currently underway using a compact and mobile dual-species interferometer, which will serve as a prototype for future high-precision tests onboard an orbiting satellite. We present recent results and improvements related to both projects.
The search for a fundamental, self-consistent theoretical framework to cover phenomena over all energy scales is possibly the most challenging quest of contemporary physics. Approaches to reconcile quantum mechanics and general relativity entail the modification of their foundations such as the equivalence principle. This corner stone of general relativity is suspected to be violated in various scenarios and is therefore under close scrutiny. Experiments based on the manipulation of cold atoms are excellently suited to challenge its different facets. Freely falling atoms constitute ideal test masses for tests of the universality of free fall in interferometric setups. Moreover, the superposition of internal energy eigenstates provides the notion of a clock, which allows to perform tests of the gravitational redshift. Furthermore, as atom interferometers constitute outstanding phasemeters, they hold the promise to detect gravitational waves, another integral aspect of general relativity. In recent years, atom interferometers have developed into versatile sensors with excellent accuracy and stability, and allow to probe physics at the interface of quantum mechanics and general relativity without classical analog. In this thesis, various aspects regarding tests of general relativity with atom interferometry have been theoretically investigated. This includes the analysis of fundamental effects as well as feasibility studies of experimental configurations. The work is partially focussed on a space-borne mission scenario for a dedicated quantum test of the universality of free fall beyond state-of-the-art by dropping matter waves of different elements. To enable the target accuracy at the level of 10^(−17), a compensation scheme has been developed and discussed, mitigating the detrimental effects of imperfect test mass co-location upon release and relaxing the requirements on the source preparation by several orders of magnitude. In addition, it was demonstrated that the careful design of quantum degenerate sources is indispensable for these experiments, requiring tailored schemes to prepare miscible binary sources. The possibility to test the gravitational redshift with atom interferometers has also been examined in this thesis and connected to the ideas of clock interferometry. With the proof that closed light pulse atom interferometers without transitions between internal internal states are not sensitive to gravitational time dilation, an ongoing scientific debate has been resolved. Instead, certain configurations were shown to implement a quantum version of the special-relativistic twin paradox, for which an experiment has been proposed. Finally, requirements on atomic sources and atom optics for scenarios of gravitational wave detection on ground and in space have been investigated.
In this article, we illustrate a series of experiments performed in our group in the field of atom interferometry for precision gravity measurements. We show that instruments measuring and testing gravity can be built both with rubidium and with strontium atoms, while keeping the sources of systematic error under control. The application of these devices in the test of the Weak Equivalence Principle with quantum objects, in the measurement of the Newtonian gravitational constant G and in the development of a new type atom interferometer for the detection of gravitational waves is discussed.
Inertial sensors based on cold atoms and light-pulse interferometry exhibit state-of-the-art sensitivity and ultra-low measurement bias that could revolutionize a variety of fields including geophysics and seismology, gravitational wave detection and fundamental tests of gravity, and inertial navigation. In the latter case, cold-atom interferometers are widely considered as breakthrough technology for future autonomous INSs. Nowadays, absolute quantum inertial sensors are available as commercial and field-deployable devices. Yet, their current size and complexity has not yet reached a technology readiness level compatible with mobile applications or plug-and-play operation by non-specialists. These systems are in desperate need of further development and miniaturization. We will present progress beyond these first experiments while exploring new methods relying on 3D matter-wave manipulation that can lead to interferometer geometries that are simultaneously sensitive to accelerations and rotations in 3D and can discern their vector components within a single measurement. These novel innovations produce additional sensitivity to rotations and gravity gradients which has not yet been exploited experimentally and could be a game changing innovation for future atomic sensors. The ability to measure the full acceleration and rotation vectors with a compact, high-precision, low-bias inertial sensor could strongly impact the fields of inertial navigation, gravity gradiometry, and gyroscopy.
The ability to control the quantum degrees of freedom of atoms using laser light opened the way to precision measurements of fundamental physical quantities. I will describe experiments for precision tests of gravitational physics using new quantum devices based on ultracold atoms, namely, atom interferometers and optical clocks. I will report on the measurement of the gravitational constant G with a Rb Raman interferometer, on experiments based on Bloch oscillations of Sr atoms confined in an optical lattice for gravity measurements at small spatial scales, and on new tests of the Einstein equivalence principle. I will also discuss prospects to use atoms as new detectors for gravitational waves and for experiments in space.
The Weak Equivalence Principle (WEP) is a central pillar of general relativity. Its precise test with quantum systems in space offers a unique window onto new physics. Here we report the first in-orbit quantum test of the WEP. A dual-species (85Rb/87Rb) atom interferometer is realized aboard the China Space Station. Methods of platform motion suppression, fluorescence detection switching, and two-photon detuning switching are developed to eliminate phase noise and improve measurement accuracy. A test uncertainty of 2.8*10-8 is obtained from 280 days of WEP test data, and a test result of (-3.1+/-4.6)*10-7 is achieved after error estimation. This improves prior atom-interferometric WEP tests in microgravity by three orders of magnitude. This work paves the way for space-borne quantum inertial sensors and their application to future fundamental physics in space.
Quantum technology based on cold-atom interferometers is showing great promise for fields such as inertial sensing and fundamental physics. However, the best precision achievable on Earth is limited by the free-fall time of the atoms, and their full potential can only be realized in Space where interrogation times of many seconds will lead to unprecedented sensitivity. Various mission scenarios are presently being pursued, which plan to implement matter-waves inertial sensors to detect gravitational waves, to measure the Earth gravity field or to test fundamental physics such as the Equivalence Principle.We developed a cold atom sensor experiment adapted to microgravity platforms, especially the ZERO-G plane. To achieve a test of the Universality of Free Fall, we realize the first onboard operation of simultaneous ^{87}Rb - ^{39}K interferometers in the weightlessness environment produced during parabolic flight. The large vibration levels (10 ^{-2} g/Hz ^{1/2}), acceleration range and rotation rates (5 deg/s) during flight present significant technical challenges for atom interferometers. By hybridizing each atomic sensor with a common mechanical accelerometer, we achieve a sensitivity of 3.4 10 ^{-5} g per shot-more than 1600 times below the ambient vibration level onboard the aircraft. We demonstrate the capability of our dual-quantum sensor by measuring the Eötvös parameter with systematic-limited uncertainties of 3.0 10 ^{-4} during micro-gravity. This constitutes the first quantum test of the equivalence principle in a free falling vehicle. Our results can be extended to the trajectory of a satellite for future Space missions. We also achieved a simultaneous ^{87}Rb- ^{39}K interferometer on ground with a long term stability on the differential acceleration measurement around 5 10 ^{-8}g, limited by the fall of the atom clouds. To increase the interrogation time and the sensitivity, a ZERO-G simulator has been installed in our laboratory and allows our experiment to be in free fall during 500 ms every 12 seconds, to achieve highly repeatable measurements in microgravity. We expect to increase our short-term sensitivity by two orders of magnitude, and consequently reach a long-term measurement of the Eötvös parameter at the level of 10 ^{-11}.To benefit from the free fall of the experiment completely, it is necessary to produce atoms clouds with a reduced velocity dispersion. To reach this goal, we put ^{87}Rb atoms in an optical dipole trap supplied by a compact fiber laser compliant with onboard applications and decrease the optical power on a very controlled way to obtain evaporative cooling. Preliminary results of ultra-fast evaporative cooling (less than a few seconds) onboard the ZERO-G plane allowed us to reach a regime of temperature compliant with an interrogation time of the order of one second. This method and technology will be tested on the ZERO-G simulator as well.