  Quantum Ising model is an exactly solvable model of quantum phase transition.
This paper gives an exact solution when the system is driven through the
critical point at finite rate. The evolution goes through a series of
Landau-Zener level anticrossings when pairs of quasiparticles with opposite
pseudomomenta get excited with probability depending on the transition rate.
Average density of defects excited in this way scales like a square root of the
transition rate. This scaling is the same as the scaling obtained when the
standard Kibble-Zurek mechanism of thermodynamic second order phase transitions
is applied to the quantum phase transition in the Ising model.
