Atom interferometry gravity-gradiometer for the determination of the Newtonian gravitational constant G

Abstract

We developed a gravity-gradiometer based on atom interferometry for the determination of the Newtonian gravitational constant G. The apparatus, combining a Rb fountain, Raman interferometry and a juggling scheme for fast launch of two atomic clouds, was specifically designed to reduce possible systematic effects. We present instrument performances and show that the sensor is able to detect the gravitational field induced by source masses. A discussion of projected accuracy for G measurement using this new scheme shows that the results of the experiment will be significant to discriminate between previous inconsistent values.

Noise-Immune Conjugate Large-Area Atom Interferometers

“…Cancellation of vibrations has been demonstrated by using the same laser light to simultaneously address two similar interferometers at separate locations [12][13][14]. This method, however, is restricted to situations where the differential signal is small (in this case, the gravity gradient), so that the interferometers are similar enough to be addressable by the same laser.…”

“…The common phase moves the data points around the ellipse, but the differential phase can be extracted by ellipse-specific fitting. One way that has been realized, without LMT [12][13][14], is to use the same radiation to address both interferometers, which trivially leads to δφ L = 0. However, the use of this method is restricted to measurements of very small differential signals, so that the interferometers are similar; whereas our SCIs are dissimilar and can be sensitive to the relatively large 16n 2 ω r T differential signal.…”

Inertial quantum sensors using light and matter

“…This configuration has been used to measure the gravity gradient of the Earth, as well as the gravity gradient associated with nearby mass distributions. Laboratory gravity gradiometers have achieved resolutions below 1 E (where 1 E = 10 −9 s −2 ) and were used to measure the gravitational constant G [53,54,55]. In addition, configurations similar to those for measuring gravity gradients can be used for gravitational wave detection [21,29,30].…”

“…As for atomic clocks, atom interferometers can also be used to measure fundamental constants at a very high level of accuracy. Present efforts include the measurement of the fine constant structure α [60], the gravitational constant G [53,54,55] and the definition of the kilogram. There are also several interesting experimental tests of General Relativity (GR), motivated by alternatives to Einstein's theory, that could be within reach with atom interferometers [18].…”

Source mass and positioning system for an accurate measurement of G

“…In our accurate measurement of G by atom interferometry ͑MAGIA͒ experiment, 14 two cold atom ensembles simultaneously fall under the effect of gravity with equal initial velocity, but being vertically displaced by 30 cm. During their motion a Raman atom interferometer 15 is operated in order to measure the vertical acceleration difference of the two samples.…”