Measurements of Gravitational Acceleration Using Frequency Domain Echo Atom Interferometry

We present measurements of gravitational acceleration using a single-state, frequency domain echo atom interferometer [Carlse et al. Phys. Rev. A 112, L061302 (2025)]. These experiments rely on the formation of an atomic matter wave lattice in the ground state of a sample of laser-cooled rubidium atoms at a temperature of ~10 µK. The lattice is formed immediately after illuminating the atomic sample with an optical running wave pulse composed of two counterpropagating travelling wave electric fields with a small relative detuning, δ. The contrast and phase of this lattice can be probed by coherently backscattering a travelling wave readout pulse. Due to the thermal energy of the atomic sample, the atomic grating dephases at a timescale governed by the velocity distribution of the sample (free induction decay or FID). The lattice can be rephased by the application of a second excitation pulse at a time t=T from the first pulse which results in the formation of a grating echo at a time t=2T. We describe grating echo gravimeter in which the running wave potentials imprint a Ramsey fringe pattern on the phase of the atomic grating and the phase of the backscattered field accumulates as gT².