  We present a novel quantum Monte Carlo method based on a path integral in
Fock space, which allows to compute finite-temperature properties of a
many-body nuclear system with a monopole pairing interaction in the canonical
ensemble. It enables an exact calculation of the thermodynamic variables such
as the internal energy, the entropy, or the specific heat, from the measured
moments of the number of hops in a path of nuclear configurations. Monte Carlo
calculations for a single-shell $(h_{11/2})^6$ model are consistent with an
exact calculation from the many-body spectrum in the seniority model.
