Quantum Control of the Spin-Orbit Interaction Using the Autler-Townes Effect

E. H. Ahmed, S. Ingram, T. Kirova, O. Salihoglu, J. Huennekens, J. Qi, Y. Guan, and A. M. Lyyra

Phys. Rev. Lett. 107, 163601 – Published 11 October 2011

Abstract

We have demonstrated quantum control of the spin-orbit interaction based on the Autler-Townes (ac-Stark) effect in a molecular system using a cw optical field. We show that the enhancement of the spin-orbit interaction between a pair of weakly interacting singlet-triplet rovibrational levels, $G {}^{1}Π_{g} (v = 12, J = 21, f) - 1 {}^{3}Σ_{g}^{-} (v = 1, N = 21, f)$ , separated by 750 MHz in the lithium dimer, depends on the Rabi frequency (laser power) of the control laser. The increase in the spin-orbit interaction due to the control field is observed as a change in the spin character of the individual components of the perturbed pair.

Received 18 May 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.163601

Authors & Affiliations

E. H. Ahmed^1,*, S. Ingram¹, T. Kirova^1,2, O. Salihoglu¹, J. Huennekens³, J. Qi⁴, Y. Guan¹, and A. M. Lyyra¹

¹Department of Physics, Temple University, Philadelphia, Pennsylvania 19122, USA
²National Institute for Theoretical Physics (NITheP), Stellenbosch 7600, South Africa
³Department of Physics, Lehigh University, Bethlehem, Pennsylvania 18015, USA
⁴Department of Physics and Astronomy, Penn State University, Berks Campus, Reading, Pennsylvania 19610, USA

^*Corresponding author. erahmed@temple.edu

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Vol. 107, Iss. 16 — 14 October 2011

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Figure 1
Thermal population in level $| 1 ⟩$ is excited to level $| 2 ⟩$ by the weak pump laser $L_{1}$ ( $15 810.158 {cm}^{- 1}$ ) and then further excited by tuning the weak probe field $L_{2}$ to the mixed pair of levels $| T ⟩$ and $| S ⟩$ , with resonances at $17 666.136$ and $17 666.162 {cm}^{- 1}$ , respectively. Laser $L_{3}$ is set on resonance with the $| S ⟩ \leftrightarrow | 3 ⟩$ transition at $17 026.872 {cm}^{- 1}$ . Levels $| S_{0} ⟩$ and $| T_{0} ⟩$ are the “pure” singlet and triplet basis states, respectively (unperturbed basis set). With the control laser on, $| S ⟩$ and $| T ⟩$ evolve into $| S, - AT ⟩$ , $| S, + AT ⟩$ , and $| T^{'} ⟩$ . The parameters $μ_{1} = 2.1 D$ , $μ_{2} = 1.8 D$ , $μ_{3} = 3.3 D$ , $τ_{2} = 18.78 ns$ , $τ_{S_{0}} = 16.21 ns$ , $τ_{T_{0}} = 9.27 ns$ , and $τ_{3} = 18.90 ns$ were calculated from molecular data [19, 21, 22, 23, 24] by using LEVEL [25].Reuse & Permissions
Figure 2
Optical–optical double resonance spectra recorded by monitoring the fluorescence to the $A {}^{1}Σ_{u}^{+} (v^{'} = 10, J^{'} = 21)$ level (singlet channel, black line) and to a few low lying rovibrational levels of the $b {}^{3}Π_{u}$ state (triplet channel, red line) as a function of the detuning of the probe laser. The control laser was blocked during these scans. The dotted lines represent simulations of the experimental spectra.Reuse & Permissions
Figure 3
(a) The singlet (black line) and triplet (red line) channel spectra recorded simultaneously in the presence of the control laser. Since the $| S, - AT ⟩$ component has acquired more triplet character (and the $| S, + AT ⟩$ component has lost triplet character), their intensities are asymmetric in opposite directions for the singlet and triplet signals. Dotted lines represent simulations. The parameters for $L_{1}$ and $L_{2}$ were the same as in Fig. 2. (b) Comparison of the singlet detection channel spectra with ( $P_{3} = 700 mW$ ) and without ( $P_{3} = 0 mW$ ) the control laser. It can be seen that the singlet character of the predominantly triplet level $1 {}^{3}Σ_{g}^{-} (v = 1, N = 21, f)$ is dramatically enhanced by the presence of the control laser.Reuse & Permissions
Figure 4
Dependence of the singlet-triplet mixing and the magnitude of the AT splitting on the control laser power. The spectra were recorded by monitoring singlet fluorescence to the $A {}^{1}Σ_{u}^{+} (v^{'} = 10, J^{'} = 21)$ level. The leftmost peak in each spectrum corresponds to fluorescence from the level $| T^{'} ⟩$ with primarily $1 {}^{3}Σ_{g}^{-} (v = 1, N = 21, f)$ character, while the peak(s) on the right correspond to fluorescence from the AT split pair of levels $| S, - AT ⟩$ and $| S, + AT ⟩$ with primarily $G {}^{1}Π_{g} (v = 12, J = 21, f)$ character.Reuse & Permissions

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