Evolution of the wave function of an atom hit by a photon in a three-grating interferometer

TL;DR

This paper analytically studies the evolution of an atom's wave function in a three-grating interferometer, explaining how interference contrast persists despite photon scattering, aligning with experimental observations.

Contribution

It provides an analytical model of atom wave function evolution in a three-grating interferometer considering photon scattering, linking contrast to the ratio of path separation and photon wavelength.

Findings

Interference contrast remains non-zero with photon scattering.

Contrast depends analytically on the ratio d_p/λ_i.

The model aligns with experimental results.

Abstract

In 1995, Chapman et al. (1995 Phys. Rev. Lett. 75 2783) showed experimentally that the interference contrast in a three-grating atom interferometer does not vanish under the presence of scattering events with photons, as required by the complementarity principle. In this work we provide an analytical study of this experiment, determining the evolution of the atom wave function along the three-grating Mach-Zehnder interferometer under the assumption that the atom is hit by a photon after passing through the first grating. The consideration of a transverse wave function in momentum representation is essential in this study. As is shown, the number of atoms transmitted through the third grating is given by a simple periodic function of the lateral shift along this grating, both in the absence and in the presence of photon scattering. Moreover, the relative contrast (laser on/laser off) is shown to be a simple analytical function of the ratio d_p/\lambda_i, where d_p is the distance between atomic paths at the scattering locus and \lambda_i the scattered photon wavelength. We argue that this dependence, being in agreement with experimental results, can be regarded to show compatibility of the wave and corpuscle properties of atoms.