About 300 experiments tried to determine the value of the Newtonian gravitational constant G to date but large discrepancies in the results prevent from knowing 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 keeping systematic effects under control. Most of the experiments performed so far were based on the torsion pendulum or torsion balance scheme as in the experiment by Cavendish 2 in 1798 and in all cases they used macroscopic masses.Here we report on the first precise determination of G using laser-cooled atoms and quantum interferometry to probe gravity. We obtain the value G= 6.67191(99) × 10 −11 m 3 kg −1 s −2with a relative uncertainty of 150 ppm. Our value is at 1.5 combined standard deviations from the current recommended value of the Committee on Data for Science and Technology (CODATA) 3 . Such a conceptually different experiment is important to identify the so far elusive systematic errors thus improving the confidence in the value of G. There is no definitive relationship indeed between G and the other fundamental constants and no theoretical pre-1 diction for its value to test the experimental results. Improving the knowledge of G has not only a pure metrological interest, but is also important for the key role that this fundamental constant plays in theories of gravitation, cosmology, particle physics, astrophysics, and geophysical models.The basic idea of our experiment is to use an atom interferometer as gravity sensor and a well-characterized mass as source of a gravitational field. From the precise measurement of the atoms' acceleration produced by the source mass and from the knowledge of the mass distribution, it is possible to extract the value of the gravitational constant G using the well-known formulaAtom interferometers 4, 5 are new tools for experimental gravitation as, for example, in precision measurements of gravity acceleration 6 and gravity gradients 7 , as gyroscopes based on the Sagnac effect 8 , for testing the 1/r 2 law 9 , general relativity 10 and quantum gravity models 11 , and for applications in geophysics 12 . Proof-of-principle experiments to measure G using atom interferometry were reported [13][14][15] . Ongoing studies show that future experiments in space will allow to take full advantage of the potential sensitivity of atom interferometers for fundamental physics tests 16 .The possibility of using atom interferometry for gravitational waves detection is being studied 17 .Since the problem in the determination of G depends on the presence of unidentified systematic errors, our experiment was designed with a double-differential configuration in order to be as immune as possible from such effects: the atomic sensor was a double interferometer in a gravity-2 gradiometer configuration, in order to subtract common-mode spurious signals, and we used two sets of well-characterized tungsten masses as source of the gravitational field that were placed in t...

We experimentally investigate and analyze the rich dynamics in F=2 spinor Bose-Einstein condensates of 87 Rb. An interplay between mean-field driven spin dynamics and hyperfine-changing losses in addition to interactions with the thermal component is observed. In particular we measure conversion rates in the range of 10 −12 cm 3 s −1 for spin changing collisions within the F=2 manifold and spin-dependent loss rates in the range of 10 −13 cm 3 s −1 for hyperfine-changing collisions. From our data we observe a polar behavior in the F=2 ground state of 87 Rb, while we measure the F=1 ground state to be ferromagnetic. Furthermore we see a magnetization for condensates prepared with non-zero total spin.PACS numbers: 03.75. Mn, 34.50.Pi, 03.75.Hh The investigation of atomic spin systems is central for the understanding of magnetism and a highly active area of research e.g. with respect to magnetic nanosystems, spintronics and magnetic interactions in high T c superconductors. In addition entangled spin systems in atomic quantum gases show intriguing prospects for quantum optics and quantum computation [1,2,3,4,5]. Bose-Einstein condensates (BEC) of ultra-cold atoms offer new regimes for studies of collective spin phenomena [6,7,8,9,10,11,12,13]. BECs with spin degree of freedom are special in the sense that their order parameter is a vector in contrast to the "common" BEC where it is a scalar. Recent extensive studies have been made in optically trapped 23 Na in the F=1 state [10,11,12,13]. In addition evidence of spin dynamics was demonstrated in optically trapped 87 Rb in the F=1 state [14]. There is current interest in extending the systems under investigation to F=2 spinor condensates [15,16,17,18,19,20], which add significant new physics. F=2 spinor condensates offer richer dynamics, an additional magnetic phase, the so-called cyclic phase [16,18], as well as intrinsic connections to d-wave superconductors [21].In this letter we present first studies of optically trapped 87 Rb F=2 spinor condensates. We measure rates for spin changing collisions for different channels within the F=2 manifold and discuss the steady state for various initial conditions. Additionally we observe and discuss the thermalization of dynamically populated m F condensates. We also present measurements of spin-dependent hyperfine decay rates of the F=2 state in 87 Rb, as a key to further understanding the intensively studied collisional properties of 87 Rb [22,23].Our experimental setup consists of a compact double MOT apparatus which produces magnetically trapped 87 Rb Bose-Einstein condensates containing 10 6 atoms in the F=2, m F = 2 state. To confine the atoms independently of their spin state they are subsequently transferred into a far detuned optical dipole trap. It is operated at 1064 nm generating trapping frequencies of typically 2π × 891 Hz vertically, 2π × 155 Hz horizontally and 2π × 21.1 Hz along the beam direction. After transfer we further cool the ensemble for 500 ms by selective parametric excitation [24] resulting in ...

We present a new measurement of the Newtonian gravitational constant G based on cold-atom interferometry. Freely falling samples of laser-cooled rubidium atoms are used in a gravity gradiometer to probe the field generated by nearby source masses. In addition to its potential sensitivity, this method is intriguing as gravity is explored by a quantum system. We report a value of G = 6.667 x 10(-11) m(3) kg(-1) s(-2), estimating a statistical uncertainty of +/-0.011 x 10(-11) m(3) kg(-1) s(-2) and a systematic uncertainty of +/-0.003 x 10(-11) m(3) kg(-1) s(-2). The long-term stability of the instrument and the signal-to-noise ratio demonstrated here open interesting perspectives for pushing the measurement accuracy below the 100 ppm level.

The theory of general relativity describes macroscopic phenomena driven by the influence of gravity while quantum mechanics brilliantly accounts for microscopic effects. Despite their tremendous individual success, a complete unification of fundamental interactions is missing and remains one of the most challenging and important quests in modern theoretical physics. The STE-QUEST satellite mission, proposed as a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), aims for testing general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by performing a test of the Universality of Free Fall of matter waves in the gravitational field of Earth comparing the trajectory of two Bose-Einstein condensates of 85 Rb and 87 Rb. The two ultracold atom clouds are monitored very precisely thanks to techniques of atom interferometry. This allows to reach down to an uncertainty in the Eötvös parameter of at least 2 · 10 −15 . In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources.

We evaluate the sensitivity of a dual cloud atom interferometer to the measurement of vertical gravity gradient. We study the influence of most relevant experimental parameters on noise and long-term drifts. Results are also applied to the case of doubly differential measurements of the gravitational signal from local source masses. We achieve a short term sensitivity of 3 × 10 −9 g/ √ Hz to differential gravity acceleration, limited by the quantum projection noise of the instrument. Active control of the most critical parameters allows to reach a resolution of 5 × 10 −11 g after 8000 s on the measurement of differential gravity acceleration. The long term stability is compatible with a measurement of the gravitational constant G at the level of 10 −4 after an integration time of about 100 hours.