  This work presents an analysis of the evolution of perturbed Bell diagonal
states using the equation of motion of steepest-entropy-ascent quantum
thermodynamics (SEAQT), the Lindblad equation, and various measures of loss of
entanglement. First, a brief derivation is presented showing that Bell diagonal
states are stationary states that are not stable equilibrium states relative to
the SEAQT equation of motion, highlighting the need for the development of
perturbation methods to study the evolutions of nearby states. This contrasts
with the Lindblad equation of motion for which only some of the Bell diagonal
states are stationary. Next, two perturbation methods are presented. The first
is a general method for perturbing bipartite systems and the second is a method
based on a set of unitary operations that are constrained to hold the system
energy and system entropy constant. Sets of density operators are randomly
generated with each method and the resulting time-varying characteristics of
the system's entanglement are analyzed. The findings reveal that the evolutions
associated with the constrained perturbations accurately predict the loss of
non-locality and align well with the measured concurrence.
