No abstract

Mobile gravimetry is important in metrology, navigation, geodesy, and geophysics. Atomic gravimeters could be among the most accurate mobile gravimeters but are currently constrained by being complex and fragile. Here, we demonstrate a mobile atomic gravimeter, measuring tidal gravity variations in the laboratory and surveying gravity in the field. The tidal gravity measurements achieve a sensitivity of 37 μGal/Hz (1 μGal = 10 nm/s2) and a long-term stability of better than 2 μGal, revealing ocean tidal loading effects and recording several distant earthquakes. We survey gravity in the Berkeley Hills with an uncertainty of around 0.04 mGal and determine the density of the subsurface rocks from the vertical gravity gradient. With simplicity and sensitivity, our instrument paves the way for bringing atomic gravimeters to field applications.

Atom interferometry has become one of the most powerful technologies for precision measurements. In order to develop simple, precise and versatile atom interferometers for inertial sensing, we demonstrate an atom interferometer measuring acceleration, rotation, and inclination by pointing Raman beams toward individual faces of a pyramidal mirror. Only a single diode laser is used for all functions, including atom trapping, interferometry, and detection. Efficient Doppler-sensitive Raman transitions are achieved without velocity selecting the atom sample, and with zero differential AC Stark shift between the cesium hyperfine ground states, increasing signal-to-noise and suppressing systematic effects. We measure gravity along two axes (vertical and 45 • to the vertical), rotation, and inclination with sensitivities of 6 µm/s 2 / √ Hz, 300 µrad/s/ √ Hz, and 4 µrad/ √ Hz, respectively. This work paves the way toward deployable multiaxis atom interferometers for geodesy, geology, or inertial navigation.

We present a hybrid laser frequency stabilization method combining modulation transfer spectroscopy (MTS) and frequency modulation spectroscopy (FMS) for the cesium D₂ transition. In a typical pump-probe setup, the error signal is a combination of the DC-coupled MTS error signal and the AC-coupled FMS error signal. This combines the long-term stability of the former with the high signal-to-noise ratio of the latter. In addition, we enhance the long-term frequency stability with laser intensity stabilization. By measuring the frequency difference between two independent hybrid spectroscopies, we investigate the short-and long-term stability. We find a long-term stability of 7.8 kHz characterized by a standard deviation of the beating frequency drift over the course of 10 h and a short-term stability of 1.9 kHz characterized by an Allan deviation of that at 2 s of integration time.

We report a compact atom interferometer in the Mach-Zehnder geometry for gravity measurement. The local gravity is measured to be 9.791 589 m s −2 with relative sensitivity ∆g reaching 2.9 × 10 −7 g in 320 s. Despite the fast development in the past two decades in the field of precision measurements, making atom interferometers transportable with guaranteed resolution for field applications is still one of the main focuses. Our compact atom interferometer aims to be functioned as an inertial sensor for field applications such as resource exploration outside of labs.