Precision measurement of the Newtonian gravitational constant using cold atoms

• Published in: Nature (London) 2014-06, Vol.510 (7506), p.518-521
• Main Authors: Rosi, G., Sorrentino, F., Cacciapuoti, L., Prevedelli, M., Tino, G. M.
• Format: Article
• Language: English
• Subjects: 639/766/36/1125; 639/766/483/1255; Atoms & subatomic particles; Experiments; Gravity; Gravity effects; Humanities and Social Sciences; Interferometry; letter; multidisciplinary; Noise; Science
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13433

Determination of the gravitational constant G using laser-cooled atoms and quantum interferometry, a technique that gives new insight into the systematic errors that have proved elusive in previous experiments, yields a value that has a relative uncertainty of 150 parts per million and which differs from the current recommended value by 1.5 combined standard deviations. A new route to big G The Newtonian gravitational constant G , also known as the universal gravitational constant or 'big G ', is a fundamental physical constant that is used in the calculation of gravitational attraction between two bodies. There are several ways to measure G with high precision, but these measurements disagree, presumably because of the intervention of unknown errors in the different experiments. With the aim of identifying and ultimately removing the systematic errors that give rise to these discrepancies, Gabriele Rosi and colleagues have carried out a high-precision measurement of G using quantum interferometry with laser-cooled atoms, an experimental approach that differs radically from previous determinations. The authors obtain a value for G with a precision of ∼0.015% — approaching that of the traditional measurements, and with prospects for considerable further improvement. Although this result doesn't yet solve the problem of the discrepant measurements, the use of such a radically different technique holds promise for identifying the systematic errors that have plagued previous determinations. About 300 experiments have tried to determine the value of the Newtonian gravitational constant, G , so far, but large discrepancies in the results have made it impossible to know its value precisely 1 . The weakness of the gravitational interaction and the impossibility of shielding the effects of gravity make it very difficult to measure G while keeping systematic effects under control. Most previous experiments performed were based on the torsion pendulum or torsion balance scheme as in the experiment by Cavendish 2 in 1798, and in all cases macroscopic masses were used. Here we report the precise determination of G using laser-cooled atoms and quantum interferometry. We obtain the value G = 6.67191(99) × 10 −11  m 3  kg −1  s −2 with a relative uncertainty of 150 parts per million (the combined standard uncertainty is given in parentheses). Our value differs by 1.5 combined standard deviations from the current recommended value of the Committee on Data for Science and T