Text S1. The measurement sequence of the
AQG-B
The measurement sequence of the AQG-B includes four main steps, that are
repeated at a frequency of 1.85 Hz (Ménoret et al., 2018; Carbone et
al., 2020). 1: 106 atoms are magneto-optically trapped
during 270 ms and cooled down to 2 µK in optical molasses. 2: The laser
is turned off and the atoms undergo a perfect free-fall. The atoms in
the \(|\left.\ F=2,m_{F}=0\right\rangle\) state are selected by
applying a microwave pulse, while the remaining atoms in the\(|\left.\ F=2\right\rangle\) level are blown away. 3: A
Mach-Zehnder atom interferometer is operated by using a sequence of
three counter-propagating stimulated Raman transitions in a\(\frac{\pi}{2}-\ \pi-\frac{\pi}{2}\) configuration, separated by an
interrogation time T = 60 ms. The atomic phase shift Φ at
the output of the interferometer is proportional to the gravitational
acceleration g of the atoms during the free fall and scales asΦ ~ (keffg-α)T² , wherekeff is the effective wavevector of the Raman
laser and α is a radio-frequency chirp applied to the Raman
lasers, in order to keep the lasers on resonance and operate the atom
interferometer around the null phaseshift. The atoms in each output port
of the interferometer are labelled by their internal state (Bordé,
1989). 4: The proportion P ~ C/2 sin Φ of
atoms in the \(|\left.\ F=2\right\rangle\) state is evaluated using
a fluorescence measurement (C is the contrast of the atom
interferometer).
All the operations are performed using a single 780 nm laser beam,
generated through frequency-doubling of 1560 nm telecom lasers and
propagated through an optical fiber to the sensor head where it is
retroreflected on a hollow pyramid reflector.