Efficiency limitation for realizing an atom-molecule adiabatic transfer based on a chainwise system

TL;DR

This paper investigates the efficiency limits of atom-molecule adiabatic transfer in a chainwise system, revealing that increasing intermediate levels can hinder transfer efficiency and proposing optimization strategies.

Contribution

It extends a previous scheme to a generalized multi-level system and analyzes the efficiency limitations, providing optimization methods for laser parameters.

Findings

Transfer efficiency is limited by the number of intermediate levels.

Optimal selection of intermediate levels is crucial for high efficiency.

Efficiency can be improved through laser parameter optimization.

Abstract

In a recent work we have developed a robust chainwise atom-molecule adiabatic passage scheme to produce ultracold ground-state molecules via photo-associating free atoms [J. Qian {\it et.al.} Phys. Rev. A 81 013632 (2010)]. With the help of intermediate auxiliary levels, the pump laser intensity requested in the atomic photo-association process can be greatly reduced. In the present work, we extend the scheme to a more generalized (2$n$+1)-level system and investigate the efficiency limitation for it. As the increase of intermediate levels and auxiliary lasers, the atom-molecule adiabatic passage would be gradually closed, leading to a poor transfer efficiency. For the purpose of enhancing the efficiency, we present various optimization approaches to the laser parameters, involving order number $n$, relative strength ratio and absolute strength. We show there can remain a limit on the population transfer efficiency given by a three-level $\Lambda$ system. In addition, we illustrate the importance of selecting an appropriate number of intermediate levels for maintaining a highly efficient transfer under mild experimental conditions.