Quantum random walks with decoherent coins

摘要: The quantum random walk has been much studied recently, largely due to its highly nonclassical behavior. In this paper, we study one possible route classical behavior for the discrete on line: presence of decoherence in ``coin'' which drives walk. We find exact analytical expressions time dependence first two moments position, and show that long-time limit variance grows linearly with time, unlike unitary compare results direct numerical simulation, see how form position distribution changes from usual result as increase strength decoherence.