Time-Resolved Rubidium-Assisted Electron Capture by Barium (II) Cation

TL;DR

This paper develops a 3D quantum simulation model to study environment-assisted electron capture in ultracold barium and rubidium atoms, providing insights into efficient state preparation for quantum technologies.

Contribution

First quantum dynamical model simulating fully three-dimensional atomic systems for environment-assisted electron capture, enabling realistic predictions and experimental feasibility assessments.

Findings

Assisted capture probability is approximately 1.9e-5% within 15 fs.

Long-lived intermediate states with 8.2e-4% probability after capture.

Model demonstrates robustness and potential for experimental realization.

Abstract

Non-local energy transfer between bound electronic states close to the ionisation threshold is employed for efficient state preparation in dilute atom systems from technological foundations to quantum computing. The generalisation to electronic transitions into and out of the continuum is lacking quantum simulations necessary to motivate such potential experiments. Here, we present the first development of a electron-dynamical model simulating fully three-dimensional atomic systems for this purpose. We investigate the viability of this model for the prototypical case of recombination of ultracold barium(II) by environment-assisted electron capture thanks to a rubidium atom in its vicinity. Both atomic sites are modelled as effective one-electron systems using the Multi Configuration Time Dependent Hartree (MCTDH) algorithm and can transfer energy by dipole-dipole interaction. We find that the simulations are robust enough to realise assisted capture over a dilute interatomic distance which we are able to quantify by comparing to simulations without interatomic energy exchange. For our current parameters not yet optimised for reaction likelihood, an environment-ionising assisted capture has a probability of $1.9\times10^{-5}~\%$ over the first $15~\mathrm{fs}$ of the simulation. The environment-exciting assisted-capture path to $[\text{Ba}^{+*}\text{Rb}^{*}]$ appears as a stable long-lived intermediate state with a probability of $8.2\times10^{-4}~\%$ for at least $20~\mathrm{fs}$ after the capture has been completed. This model shows potential to predict optimised parameters as well as to accommodate the conditions present in experimental systems as closely as possible. We put the presented setup forward as a suitable first step to experimentally realise environment-assisted electron capture with current existing technologies.