  Perturbing a Virasoro minimal model by the (1,3) primary bulk field results
in an integrable field theory. In this paper, an infinite set of commuting
conserved charges is obtained by considering defects: a one-parameter family of
perturbed defect operators is given, and it is shown that these operators
mutually commute, that they commute with the Hamiltonian of the perturbed CFT,
and that they satisfy a T-system functional relation. The formulation in terms
of perturbed defects is a modification of the original prescription for such
charges by Bazhanov, Lukyanov and Zamolodchikov.
