126 research outputs found
Measuring the Density Matrix by Local Addressing
We introduce a procedure to measure the density matrix of a material system.
The density matrix is addressed locally in this scheme by applying a sequence
of delayed light pulses. The procedure is based on the stimulated Raman
adiabatic passage (STIRAP) technique. It is shown that a series of population
measurements on the target state of the population transfer process yields
unambiguous information about the populations and coherences of the addressed
states, which therefore can be determined.Comment: 4 pages, 1 figur
Transition times in the Landau-Zener model
This paper presents analytic formulas for various transition times in the
Landau-Zener model. Considerable differences are found between the transition
times in the diabatic and adiabatic bases, and between the jump time (the time
for which the transition probability rises to the region of its asymptotic
value) and the relaxation time (the characteristic damping time of the
oscillations which appear in the transition probability after the crossing).
These transition times have been calculated by using the exact values of the
transition probabilities and their derivatives at the crossing point and
approximations to the time evolutions of the transition probabilities in the
diabatic basis, derived earlier \protect{[}N. V. Vitanov and B. M. Garraway,
Phys. Rev. A {\bf 53}, 4288 (1996)\protect{]}, and similar results in the
adiabatic basis, derived in the present paper.Comment: 7 pages, two-column revtex style, 5 figures, to appear in Phys. Rev.
A (Feb 1999
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