Open quantum random walks on the half-line: the Karlin-McGregor formula, path counting and Foster's Theorem

Thomas S. Jacq, Carlos F. Lardizabal

Published 2017-01-29Version 1

In this work we consider open quantum random walks on the non-negative integers. By considering orthogonal matrix polynomials we are able to describe transition probability expressions for classes of walks via a matrix version of the Karlin-McGregor formula. We focus on absorbing boundary conditions and, for simpler classes of examples, we consider path counting and the corresponding combinatorial tools. A non-commutative instance of the gambler's ruin is studied, expressions for the probability of reaching a certain fortune and the mean time to reach a fortune or ruin are described via a counting technique for boundary restricted paths in a lattice, due to Kobayashi et al. We also discuss an open quantum version of Foster's Theorem for the expected return time.