Abstract We construct a quasi-inertial reference system for the atom interferometer in terms of the light-field compensation, which is equivalent to the establishment of a quantum drag-free system. The compensation considered in our approach involves feedbacks of both classical and quantum nature. As a result, it may significantly reduce the dependence of the interferometric phase shift on the atomic initial position and velocity. As the error bound for gravity experiments originates primarily from the uncertainties in the initial conditions, the proposed quasi-inertial reference system might lead to substantial improvement in this regard. To be specific, the refined process introduced in the present study gives rise to the possibility of the measurement of the Newtonian gravitational constant G beyond the precision level of 10 −6 , as well as the test of the weak equivalence principle beyond 10 −14 . Moreover, when compared with the conventional quasi-inertial reference based on macroscopic objects, additional quantum feedback plays an essential role concerning both theoretical rigor and practical performance enhancement. We further explore the possibility of implementing the proposed quasi-inertial reference system in ongoing experimental developments.
Abstract We construct a quasi-inertial reference system for the atom interferometer in terms of the light-field compensation, which is equivalent to the establishment of a quantum drag-free system. The compensation considered in our approach involves feedbacks of both classical and quantum nature. As a result, it may significantly reduce the dependence of the interferometric phase shift on the atomic initial position and velocity. As the error bound for gravity experiments originates primarily from the uncertainties in the initial conditions, the proposed quasi-inertial reference system might lead to substantial improvement in this regard. To be specific, the refined process introduced in the present study gives rise to the possibility of the measurement of the Newtonian gravitational constant G beyond the precision level of 10 −6 , as well as the test of the weak equivalence principle beyond 10 −14 . Moreover, when compared with the conventional quasi-inertial reference based on macroscopic objects, additional quantum feedback plays an essential role concerning both theoretical rigor and practical performance enhancement. We further explore the possibility of implementing the proposed quasi-inertial reference system in ongoing experimental developments.
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.
Cold-atom interferometer based on stimulated Raman transition is interesting for both fundamental researches and precision measurements. Measuring g, the free fall acceleration, plays an important role in these applications. We describe the theory of atom interferometry, including the evolution of the atomic wavepacket in gravity field, the laser-atom interaction, and the interference of the atomic waves. In this article, we introduce the procedure of measuring g using atom interferometer, the experimental setup, and the tendency of the future development. The works of the domestic and international groups for g measurement are concluded. Furthermore, the noise limits and dominant systematic effects in atom gravimeters are analyzed. The suppressions of the background vibration, the Raman phase noise, and the evaluation of the main systematic effects, are introduced. Finally, the other applications using the atom interferometers for precision measurement are presented, such as in measuring the Newton’s gravitational constant, in testing the weak equivalence principle and the other fundamental applications in physics studies.
Abstract With the rapid development of atom interferometry, atom interferometers have been widely used in inertial navigation, resource exploration, basic physics and other fields. For precise measurement experiments with multi-loop atom interferometer configuration, it is urgent to establish a high-precision theoretical model charactering the relationship between target measurement quantities and measurement results. Based on this, we adopt the idea of co-moving reference frame, so as to transfer the gravity, gravity gradient and Earth’s rotation effects to the laser light field interacting with atoms by translating, rotating and stretching the background spacetime. With this method, we not only can simplify the analysis process of the experimental principle, but also give the analytical results of the high-order interference phase of the multi-loop atom interferometer containing the gravity gradient and Earth’s rotation. This work will lay a certain theoretical foundation for higher-precision experiment, and will also help to clearly guide the implementation of the experiment.
Atom interferometry tests of universality of free fall based on the differential measurement of two different atomic species provide a useful complement to those based on macroscopic masses. However, when striving for the highest possible sensitivities, gravity gradients pose a serious challenge. Indeed, the relative initial position and velocity for the two species need to be controlled with extremely high accuracy, which can be rather demanding in practice and whose verification may require rather long integration times. Furthermore, in highly sensitive configurations gravity gradients lead to a drastic loss of contrast. These difficulties can be mitigated by employing wave packets with narrower position and momentum widths, but this is ultimately limited by Heisenberg's uncertainty principle. We present a promising scheme that overcomes these problems by compensating the effects of the gravity gradients and circumvents the fundamental limitations due to Heisenberg's uncertainty principle. Furthermore, it relaxes the experimental requirements on initial colocation by several orders of magnitude.
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.
Quantum interferometer gravity gradiometer for 3D mapping is a project for developing the technology of atom interferometer-based gravity sensor in space. The atom interferometer utilizes atomic particles as free fall test masses to measure inertial forces with unprecedented sensitivity and precision. It also allows measurements of the gravity gradient tensor components for 3D mapping of subsurface mass distribution. The overall approach is based on recent advances of laser cooling and manipulation of atoms in atomic and optical physics. Atom interferometers have been demonstrated in research laboratories for gravity and gravity gradient measurements. In this approach, atoms are first laser cooled to micro-kelvin temperatures. Then they are allowed to freefall in vacuum as true drag-free test masses. During the free fall, a sequence of laser pulses is used to split and recombine the atom waves to realize the interferometric measurements. We have demonstrated atom interferometer operation in the Phase I period, and we are implementing the second generation for a complete gradiometer demonstration unit in the laboratory. Along with this development, we are developing technologies at component levels that will be more suited for realization of a space instrument. We will present an update of these developments and discuss the future directions of the quantum gravity gradiometer project.