  The statistics of work performed on a system by a sudden random quench is
investigated. Considering systems with finite dimensional Hilbert spaces we
model a sudden random quench by randomly choosing elements from a Gaussian
unitary ensemble (GUE) consisting of hermitean matrices with identically,
Gaussian distributed matrix elements. A probability density function (pdf) of
work in terms of initial and final energy distributions is derived and
evaluated for a two-level system. Explicit results are obtained for quenches
with a sharply given initial Hamiltonian, while the work pdfs for quenches
between Hamiltonians from two independent GUEs can only be determined in
explicit form in the limits of zero and infinite temperature.
