  We present an example of quantum process tomography (QPT) performed on a
single solid state qubit. The qubit used is two energy levels of the triplet
state in the Nitrogen-Vacancy defect in Diamond. Quantum process tomography is
applied to a qubit which has been allowed to decohere for three different time
periods. In each case the process is found in terms of the chi matrix
representation and the affine map representation. The discrepancy between
experimentally estimated process and the closest physically valid process is
noted. The results of QPT performed after three different decoherence times are
used to find the error generators, or Lindblad operators, for the system, using
the technique introduced by Boulant et al. [N. Boulant, T.F. Havel, M.A. Pravia
and D.G. Cory, Phys. Rev. A 67, 042322 (2003)].
