  Theoretical analyses of ultrafast spin dynamics commonly address and discuss
simulated phenomena by means of observables, whereas in quantum information
theory one often utilizes measures of quantum states. In this Paper we report
on possible benefits of quantum information measures in simulations of
ultrafast spin dynamics. For Co/Cu heterostructures illuminated by femtosecond
laser pulses, we discuss the general behaviour of quantum information measures,
in particular distances in Hilbert space and degrees of mixing in the density
matrix. The measures are in particular sensitive to variations of the
polarization of a laser pulse and the sample composition. Moreover, they are
closely related to magnetization and number of excited electrons.
