Precision Gravity Tests with Atom Interferometry in Space

Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6·10 −4 % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 10 5 . We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space.

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“…Different aspects of the STE-QUEST mission are described in Ref. [6][7][8][9]. The specific requirements for STE-QUEST are derived in Ref.…”

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confidence: 99%

Atom interferometry in space: Thermal management and magnetic shielding

Milke

Kubelka-Lange

Gürlebeck

et al. 2014

Review of Scientific Instruments

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“…We expect it to be the dominant force on polarizable objects over a large temperature range 1 and thus important in atom interferometry, nanomechanics or optomechanics 12 . Controlling this force will enable higher precision in atom interferometers, including tests of fundamental physics such as of the equivalence principle [13][14][15] , planned searches for dark matter and dark energy 16 , gravity gradiometry 17,18 , inertial navigation and perhaps even Casimir force measurements and gravitational wave detection 19,20 .…”

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confidence: 99%

Attractive force on atoms due to blackbody radiation

Haslinger

Jaffe

et al. 2017

Nature Phys

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Objects at finite temperature emit thermal radiation with an outward energy-momentum flow, which exerts an outward radiation pressure. At room temperature, a caesium atom scatters on average less than one of these blackbody radiation photons every 10 8 years. Thus, it is generally assumed that any scattering force exerted on atoms by such radiation is negligible. However, atoms also interact coherently with the thermal electromagnetic field. In this work, we measure an attractive force induced by blackbody radiation between a caesium atom and a heated, centimetre-sized cylinder, which is orders of magnitude stronger than the outward-directed radiation pressure. Using atom interferometry, we find that this force scales with the fourth power of the cylinder's temperature. The force is in good agreement with that predicted from an a.c. Stark shift gradient of the atomic ground state in the thermal radiation field 1 . This observed force dominates over both gravity and radiation pressure, and does so for a large temperature range. Quantum technology continues to turn formerly unmeasurable effects into technologically important physics. For example, minuscule shifts of atomic energy levels due to room-temperature blackbody radiation have become leading influences in atomic clocks at or beyond the 10 −14 level of accuracy 2 . They have thus become important to precision timekeeping 3 , and for applications such as improving time standards, relativistic geodesy and searches for variations of fundamental constants. Thermal radiation from a heated source should also result in a repulsive radiation pressure on atoms through absorption of photons [4][5][6][7] . However, the scattering rate for room-temperature blackbody radiation is small, leading to only mm s −1 velocity changes in hundreds of thousands of years for the caesium D line, for example. Here, we show that spatially inhomogeneous blackbody radiation produces a much higher acceleration at the μ m s −2 level pointing towards the source, even near room temperature. It is well described by the intensity gradient of blackbody radiation that gives rise to a spatially dependent a.c. . We expect it to be the dominant force on polarizable objects over a large temperature range 1 and thus important in atom interferometry, nanomechanics or optomechanics 12 . Controlling this force will enable higher precision in atom interferometers, including tests of fundamental physics such as of the equivalence principle [13][14][15] , planned searches for dark matter and dark energy 16 , gravity gradiometry 17,18 , inertial navigation and perhaps even Casimir force measurements and gravitational wave detection 19,20 .As shown in Fig. 1, we perform atom interferometry with caesium atoms 21 in an optical cavity to measure the force induced by blackbody radiation. Our setup is similar to the one we used previously 22,23 . Caesium atoms act as matter waves in our experiment. They are laser-cooled to a temperature of about 300 nK and launched upwards into free fall, reaching 3.7 mm into t...

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“…Accelerometers based on atom interferometry have been developed for many practical applications including geodesy, geophysics, engineering prospecting, and inertial navigation [20][21][22]. Instruments for space-based research are being conceived for different applications ranging from weak equivalence principle tests and gravitational-wave detection to geodesy [23,24].One of the most attractive features of atom interferometry sensors is the ability to perform differential acceleration measurements by simultaneously interrogating two separated atomic clouds with high rejection of common-mode vibration noise, as demonstrated in gravity gradiometry applications [3,9]. In principle, such a scheme can be extended to an arbitrary number of samples, thus, providing a measurement of higher-order spatial derivatives of the gravity field.…”

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confidence: 99%

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confidence: 99%

Measurement of the Gravity-Field Curvature by Atom Interferometry

et al. 2015

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We present the first direct measurement of the gravity-field curvature based on three conjugated atom interferometers. Three atomic clouds launched in the vertical direction are simultaneously interrogated by the same atom interferometry sequence and used to probe the gravity field at three equally spaced positions. The vertical component of the gravity-field curvature generated by nearby source masses is measured from the difference between adjacent gravity gradient values. Curvature measurements are of interest in geodesy studies and for the validation of gravitational models of the surrounding environment. The possibility of using such a scheme for a new determination of the Newtonian constant of gravity is also discussed.In the last two decades, atom interferometry [1] has profoundly changed precision inertial sensing, leading to major advances in metrology and fundamental and applied physics. The outstanding stability and accuracy levels [2,3] combined with the possibility of easily implementing new measurement schemes [4][5][6][7] are the main reasons for the rapid progress of these instruments. Matter-wave interferometry has been successfully used to measure local gravity [8], gravity gradient [9-11], the Sagnac effect [12], the Newtonian gravitational constant [13][14][15][16], the fine structure constant [17], and for tests of general relativity [18,19]. Accelerometers based on atom interferometry have been developed for many practical applications including geodesy, geophysics, engineering prospecting, and inertial navigation [20][21][22]. Instruments for space-based research are being conceived for different applications ranging from weak equivalence principle tests and gravitational-wave detection to geodesy [23,24].One of the most attractive features of atom interferometry sensors is the ability to perform differential acceleration measurements by simultaneously interrogating two separated atomic clouds with high rejection of common-mode vibration noise, as demonstrated in gravity gradiometry applications [3,9]. In principle, such a scheme can be extended to an arbitrary number of samples, thus, providing a measurement of higher-order spatial derivatives of the gravity field. Geophysical models of the Earth's interior rely on the inversion of gravity and gravity gradient data collected at or above the surface [25]. The solution to this problem, which is, in general, not unique, leads to images of the subsurface mass distribution over different scale lengths [26]. In this context,

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Precision Gravity Tests with Atom Interferometry in Space

Cited by 81 publications

References 25 publications

Atom interferometry in space: Thermal management and magnetic shielding

Atom interferometry in space: Thermal management and magnetic shielding

Attractive force on atoms due to blackbody radiation

Measurement of the Gravity-Field Curvature by Atom Interferometry

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