Matter-Wave Decoherence due to a Gas Environment in an Atom Interferometer

Decoherence due to scattering from background gas particles is observed for the first time in a Mach-Zehnder atom interferometer, and compared with decoherence due to scattering photons. A single theory is shown to describe decoherence due to scattering either atoms or photons. Predictions from this theory are tested by experiments with different species of background gas, and also by experiments with different collimation restrictions on an atom beam interferometer.

Figure 1

Comparison of photon decoherence (left) to gas decoherence (right). Contrast and intensity in an atom beam interferometer are reported as a function of resonant laser beam power or background gas pressure. The curves come from a general theory of decoherence given by Eqs. (2, 3).

Figure 2

Schematic of the atom interferometer and scattering scenarios. For gas decoherence the entire interferometer is exposed to background gas, allowing scattering to take place anywhere along both arms of the interferometer. Previous experiments [7, 8, 9] studied photon scattering from the two arms at a location where the separation vector $\mathbf{d}$ is defined.

Figure 3

Contrast and intensity shown in parametric plots as a function of the pressure of the background gas. (a) Various background gas species provide similar results. (b) Large atom beams cause more rapid loss of contrast. Theory curves are from Eqs. (4, 5).