Molecular Feshbach dissociation as a source for motionally entangled atoms

TL;DR

This paper presents an analytic model for dissociating Feshbach molecules using magnetic field pulses to produce motionally entangled ultracold atoms, enabling potential quantum interferometry and Bell tests.

Contribution

It derives an explicit expression for the asymptotic two-atom state post-dissociation, linking magnetic pulse shape to entanglement quality, advancing control over ultracold atom entanglement generation.

Findings

Square magnetic pulses minimize atomic momentum spread.

The dissociation protocol can produce macroscopically distinct entangled wave packets.

The model supports improved Bell test experiments with ultracold atoms.

Abstract

We describe the dissociation of a diatomic Feshbach molecule due to a time-varying external magnetic field in a realistic trap and guide setting. An analytic expression for the asymptotic state of the two ultracold atoms is derived, which can serve as a basis for the analysis of dissociation protocols to generate motionally entangled states. For instance, the gradual dissociation by sequences of magnetic field pulses may delocalize the atoms into macroscopically distinct wave packets, whose motional entanglement can be addressed interferometrically. The established relation between the applied magnetic field pulse and the generated dissociation state reveals that square-shaped magnetic field pulses minimize the momentum spread of the atoms. This is required to control the detrimental influence of dispersion in a recently proposed experiment to perform a Bell test in the motion of the two atoms [C. Gneiting and K. Hornberger, Phys. Rev. Lett. 101, 260503 (2008)].