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 interferometers require precise control of digital, analog, and radio frequency signals for effective operation. In this paper, we propose and implement a control system for mobile atom interferometers. The system consists of a microcontroller and peripherals to synthesize radio frequency signals and to read or write analog signals. We use the system to operate a mobile atomic gravimeter by controlling 7 analog outputs, 16 digital outputs, 2 radio frequency channels, and 1 analog input. Our control system eliminates dead time between repetitions of the measurement and, consequently, improves the sampling rate of our atomic gravimeter by more than a factor of 2 and the sensitivity by more than a factor of √ 2 compared to the system based on a desktop computer.
We demonstrate a mobile quantum gravimeter measuring tidal gravity variations in the laboratory and surveying gravity in the field. With simplicity and sensitivity, our instrument paves the way for bringing quantum sensors to field applications.
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