N. Imoto, CONTROLLING 2-LEVEL ATOMS WITH A QUANTIZED PI OR PI 2 PULSE/, Progress in crystal growth and characterization of materials, 33(1-3), 1996, pp. 295-301
We discuss the quantum effect of the optical control field such as a p
i pulse and a pi/2 pulse on the decoherence of a two-level system to b
e controlled in the experiments such as atom interference and quantum
computation. A general solution for the Jaynes-Cummings model is obtai
ned for this purpose, and the reduced density operator of the controll
ed two-level atom after the interaction is calculated. Examining typic
al initial quantum states for the control field such as number state,
large-amplitude coherent state and small-amplitude coherent state, we
can compare these states in the scope of atomic coherence controllabil
ity. It became clear that a number state field mostly destroys the pur
ity of the two-level atom, and that a large-amplitude coherent state i
s ideal (except that large energy is required to control the atomic st
ate). Use of a coherent state with considerably small photon number wi
ll cause decoherence, but not too much.