F. Sorrentino

Long-lived bloch oscillations with bosonic Sr atoms and application to gravity measurement at the micrometer scale

We report on the observation of Bloch oscillations on the unprecedented time scale of several seconds. The experiment is carried out with ultracold bosonic 88Sr atoms loaded into a vertical optical standing wave. The negligible atom-atom elastic cross section and zero angular momentum in the ground state makes 88Sr an almost ideal Bose gas, insensitive to typical mechanisms of decoherence due to thermalization and external stray fields. The small size of the system enables precision measurements of forces at micrometer scale. This is a challenge in physics for studies of surfaces, Casimir effects, and searches for deviations from Newtonian gravity predicted by theories beyond the standard model.

Quantum tests of the Einstein Equivalence Principle with the STE-QUEST space mission

We present in detail the scientific objectives in fundamental physics of the Space-Time Explorer and QUantum Equivalence Space Test (STE-QUEST) space mission. STE-QUEST was pre-selected by the European Space Agency together with four other missions for the cosmic vision M3 launch opportunity planned around 2024. It carries out tests of different aspects of the Einstein Equivalence Principle using atomic clocks, matter wave interferometry and long distance time/frequency links, providing fascinating science at the interface between quantum mechanics and gravitation that cannot be achieved, at that level of precision, in ground experiments. We especially emphasize the specific strong interest of performing equivalence principle tests in the quantum regime, i.e. using quantum atomic wave interferometry. Although STE-QUEST was finally not selected in early 2014 because of budgetary and technological reasons, its science case was very highly rated. Our aim is to expose that science to a large audience in order to allow future projects and proposals to take advantage of the STE-QUEST experience.

Precision gravimetry with atomic sensors

Atom interferometers have been shown to be very stable and accurate sensors for acceleration and rotation. In this paper we review the applications of atom interferometry to gravity measurements, with a special emphasis on the potential impact of these techniques on applied science fields.

Sensitivity limits of a Raman atom interferometer as a gravity gradiometer

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^(-1/2) 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.

Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant

We present here the current status of our high-sensitivity gravity- gradiometer based on atom interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are launched in a fountain configuration and simultaneously interrogated by a Raman-pulse interferometry sequence. The system has recently been upgraded and its stability re-evaluated. We also discuss the recent progress of the experiment towards a precise determination of the Newtonian gravitational constant G. The signal-to-noise ratio and the long-term stability of the gravity gradiometer demonstrated interesting perspectives for pushing the G measurement precision below the 100ppm level.

Quantum sensor for atom-surface interactions below10μm

We report the realization of a quantum device for force sensing at the micrometric scale. We trap an ultracold

Cooling and trapping of ultracold strontium isotopic mixtures

^{88}\mathrm{Sr}

Laser Cooling and Trapping of Atomic Strontium for Ultracold Atoms Physics, High-Precision Spectroscopy and Quantum Sensors

atomic cloud with a one-dimensional (1D) optical lattice; then we place the atomic sample close to a test surface using the same optical lattice as an elevator. We demonstrate precise positioning of the sample at the micrometer scale. By observing the Bloch oscillations of atoms into the 1D optical standing wave, we are able to measure the total force on the atoms along the lattice axis, with a spatial resolution of few micrometers. We also demonstrate a technique for transverse displacement of the atoms, allowing us to perform measurements near either transparent or reflective test surfaces. In order to reduce the minimum distance from the surface, we compress the longitudinal size of the atomic sample by means of an optical tweezer. This system is suited for studies of atom-surface interaction at short distance, such as measurement of the Casimir force and the search for possible non-Newtonian gravity effects.

Cooling of Sr to high phase-space density by laser and sympathetic cooling in isotopic mixtures

We present the simultaneous cooling and trapping of an isotopic mixture in a magneto-optical trap and describe the transfer of the mixture into a conservative, far-off-resonant dipole trap. The mixture is prepared with a technique that applies to intermediate and heavy alkaline-earth-metal-like atoms. In this work,

iSense: A Portable Ultracold-Atom-Based Gravimeter

^{88}\mathrm{Sr}