Quantum diffraction of wave function in time-domain

The transition of a two-level system driven by a linearly weak chirped pulse is studied. Under the first order perturbation approximation, an analytical expression of the population probability is obtained, which is similar to the one describing Fresnel diffraction by a straight edge. It is shown that the population oscillation results from the diffraction of quantum wave function in time-domain. Supported by the Natural Science Foundation of Shaanxi Province of China (Grant No. 2007A04)