Electric Rydberg-atom interferometry has been performed with helium atoms in coherent superpositions of the $1s56s{}^{3}S_1$ and $1s57s{}^{3}S_1$ Rydberg levels. The experiments were carried out in a longitudinal geometry with the atoms traveling at 2000 m/s in pulsed supersonic beams. After laser photoexcitation from the $1s2s{}^{3}S_1$ metastable level, coherent manipulation of the population of the Rydberg states was achieved using sequences of microwave pulses. The difference in the static electric dipole polarizabilities of the $1s56s{}^{3}S_1$ and $1s57s{}^{3}S_1$ levels allowed superpositions of external momentum states to be generated when inhomogeneous electric fields were used to exerted forces on the atoms prepared in superpositions of these internal states. Interference fringes, with contributions arising from the spatial separation of these Rydberg-atom wave packets in the direction of propagation of the atomic beam, were identified through changes in the internal-state populations as the magnitudes and durations of the time-dependent electric-field gradient pulses were adjusted. The maximal displacement of the atomic wave packets for which interference fringes were observed was $\sim 0.75\mathrm{nm}$, limited by the longitudinal velocity spread in the atomic beam and the characteristics of the inhomogeneous electric-field distribution in the apparatus. The experimental data are in good quantitative agreement with the results of numerical calculations of the time evolution of the atomic states under the experimental conditions.

• Received 4 February 2021
• Revised 7 July 2021
• Accepted 6 August 2021

DOI:https://doi.org/10.1103/PhysRevA.104.033305