关键词: 受激拉曼绝热通道/
布居转移/
绝热条件/
纠缠态
English Abstract
Theoretical research on an efficient population transfer based on two different laser pulse sequences
Zhang Lu,Yan Lu-Yao,
Bao Hui-Han,
Chai Xiao-Qian,
Ma Dan-Dan,
Wu Qian-Nan,
Xia Ling-Chen,
Yao Dan,
Qian Jing
1.Quantum Institute for Light and Atoms, Department of Physics and Material Science, East China Normal University, Shanghai 200062, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11474094, 11104076).Received Date:23 May 2017
Accepted Date:11 July 2017
Published Online:05 November 2017
Abstract:A quantum gas of ultracold molecules, with long-range and anisotropic interactions, will enable a series of fundamental studies in physics and chemistry. In particular, samples of ground-state molecules at ultralow temperatures and high number densities will facilitate the explorations of a large number of many-body physical phenomena and applications in quantum information processing. However, due to the lack of efficiently cooling techniques such as laser cooling for atomic gases, high number densities for ultracold molecular samples are not readily attainable. Associating ultracold atoms to weakly bound dimer molecules via Feshbach resonance and subsequently transferring them to a wanted molecular ro-vibronic ground state by a stimulated Raman adiabatic passages (STIRAP) have proved to be an effective way in producing ideal ultracold molecular samples. As a typical illustration, in a recent study (2010 Nat. Phys. 6 265) Danzl et al. experimentally realized the preparation of Cs2 molecule into its ro-vibronic ground state via two different multi-level STIRAPs:one is based on a single conversion route and the others are based on a cascade-connected route (labeled by 4p-STIRAP and s-STIRAP, respectively). In this work, we present a theoretical study for these two STIRAP schemes, focusing on the differences in physical principle and realistic performance between them. On the one hand, according to the theoretical approach of quasi-dark eigenstates, we conclude that a highly efficient population transfer is achievable in both schemes. On the other hand, by systematically studying the influences of the relevant parameters, including the spontaneous decays and the detunings from the intermediate states, and the temporal sequence and the amplitude of the laser pulses, we disclose their respective advantages and weaknesses in the realistic implementation. We theoretically predict that for both schemes their maximal conversion efficiencies each can attain 0.97 as long as the spontaneous decays from the intermediate excited states are sufficiently suppressed. Yet considering the fact that the already implemented efficiency is only around 0.6 for both schemes, there is still room for optimization, e.g. using stable Rydberg energy levels in future experiment. Furthermore, the success of these two schemes can provide a new route to the controllable entanglement preparation, opening more applications in the fields of quantum logic gate and so on.
Keywords: stimulated Raman adiabatic process/
population transfer/
adiabatic condition/
entangled state
