  The phase space of quantum mechanics can be viewed as the complex projective
space endowed with a Kaehlerian structure given by the Fubini-Study metric and
an associated symplectic form. We can then interpret the Schrodinger equation
as generating a Hamiltonian dynamics. Based upon the geometric structure of the
quantum phase space we introduce the corresponding natural microcanonical and
canonical ensembles. The resulting density matrix for the canonical ensemble
differs from density matrix of the conventional approach. As an illustration,
the results are applied to the case of a spin one-half particle in a heat bath
with an applied magnetic field.
