  When a two-level quantum system is irradiated with a microwave signal, in
resonance with the energy difference between the levels, it starts Rabi
oscillation between those states. If there are other states close, in energy,
to the first two, the Rabi signal will also induce transition to those. Here,
we study the probability of transition to the third state, in a three-level
system, while a Rabi oscillation between the first two states is performed. We
investigate the effect of pulse shaping on the probability and suggest methods
for optimizing pulse shapes to reduce transition probability.
