Large deviations for quantum Markov semigroups on the 2 x 2 matrix algebra

Abstract

Let $({\mathcal{T}}_{*t})$ be a predual quantum Markov semigroup acting on the full 2 x 2 matrix algebra and having an absorbing pure state. We prove that for any initial state $\omega$, the net of orthogonal measures representing the net of states $({\mathcal{T}}_{*t}(\omega))$ satisfies a large deviation principle in the pure state space, with a rate function given in terms of the generator, and which does not depend on $\omega$. This implies that $({\mathcal{T}}_{*t}(\omega))$ is faithful for all $t$ large enough. Examples arising in weak coupling limit are studied.