EGAS41 - Swansea University

41 st EGAS CP 3 Gdańsk 2009
Population transfer in four-level atomic or molecular systems
with far-optical transitions
H.K. Avetissian 1,∗ , A. Brown 2 , G.F. Mkrtchian 1
1 Centre of Strong Fields Physics, Yerevan State University, 1 A. Manukian,
Yerevan 0025, Armenia
2 Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2
∗ Corresponding author: avetissian@ysu.am
The possibilities to control quantum systems, e.g., to obtain desired coherent superposition
states using external electromagnetic fields, have been studied intensively during the
many decades since the period of development of the Nonlinear Optics and are considered
nowadays because of their significance for implementation of contemporary problems in
Quantum Informatics. The techniques which allow robust transfer of population between
the specified states in quantum systems are of interest. From this point of view, adiabatic
passage in atomic and molecular systems is a well established tool to achieve this goal.
The main advantage of processes based on adiabatic passage is their relative robustness
against the fluctuations of the characteristic parameters in experiments (such as the pulse
area). However, the control of population transfer is problematic in quantum systems
where the main transitions are at least in the UV domain. In these cases, the problem requires
multiphoton excitation. The latter is effective if the energies of the excited states of
a three-level atomic configuration are close to each other with a nonzero transition dipole
moment [1], otherwise the states of the system should possess mean dipole moments [2].
In the present work, we propose the multiphoton adiabatic population transfer mechanism
in four-level systems with far-optical transitions via the two dipole coupled quantum
states close to each other, or with a mean dipole moment in the excited states (for a three
state system with this configuration, the multiphoton population transfer mechanism resembles
“multiphoton STIRAP”, see [3, 4]). In the considered model systems, the two
coupling laser fields induce multiphoton transitions between the initial and target states,
which we call IMAP - induced multiphoton adiabatic passage. The time evolution of such
systems is found analytically by the developed nonperturbative multiphoton resonant
theory for atom-two strong waves interaction. Performing also numerical simulations, we
show that by using two time-delayed-overlapping laser pulses it is possible to produce
the complete population transfer in quantum systems with high energy transitions. The
proposed IMAP schemes for four-level quantum systems of high energy transitions may
have diverse applications for molecules or molecular ions, as well as for hydrogen-like
atoms/ions with the required structure due to the Coulomb random degeneration.
Acknowledgment
This work was supported by International Science and Technology Center (ISTC) Project No.
A-1307.
References
[1] H.K. Avetissian, G.F. Mkrtchian, Phys. Rev. A 66, 033403 (2002)
[2] A. Brown, W.J. Meath, P. Tran, Phys. Rev. A 63, 013403 (2000)
[3] H.K. Avetissian, G.F. Mkrtchian, ECAMP IX, Abstract Book Mo4-27 (2007)
[4] A. Brown, Chemical Physics 342, 16 (2007)
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