Figure 1
From: Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter
Left: picture of the first Absolute Quantum Gravimeter (AQG-A01). The system can be setup at a measurement location in less than 20 min, warm-up time is of the order of 1 h. The sensor head weighs approximately 30 kg. It is mounted on an adjustable tripod with precision leveling titanium-tipped feet that can be adapted to various terrains. The measurement height is 55 cm. Right: sketch of the sensor head and measurement principle24. Approximately 107 atoms are loaded in a magneto-optical trap (MOT) inside the pyramid and cooled down to 2 μK. The π/2 − π − π/2 atom interferometry sequence is performed once the atoms are in free-fall. At the end of the sequence, we collect fluorescence on a set of photodiodes and compute the proportion of atoms in each output port of the interferometer, labeled by their internal state. A high-precision accelerometer is attached to the top of the vacuum chamber, as close as possible to the pyramidal reflector. Its signal is used to apply a real-time correction to the laser phase, in order to reject seismic noise. Two tiltmeters and a barometer are also attached to the sensor to ensure high accuracy and long-term stability of the gravity measurement.
