Almost zero transfer in continuous-time quantum walks on weighted tree graphs

Abstract: We study the probability flux on the central vertex in continuous-time quantum walks on weighted tree graphs. In a weighted graph, each edge has a weight we call hopping. This hopping sets the jump rate of the particle between the vertices connected by the edge. Here, the edges of the central vertex (root) have a hopping parameter $J$ larger than those of the other edges. For star graphs, this hopping gives only how often the walker visits the central vertex over time. However, for weighted spider graphs $S_{n,2}$ and $S_{n,3}$, the probability on the central vertex drops with $J^2$ for walks starting from a state of any superposition of leaf vertices. We map Cayley trees $C_{3,2}$ and $C_{3,3}$ into these spider graphs and observe the same dependency. Our results suggest this is a general feature of such walks on weighted trees and a way of probing decoherence effects in an open quantum system context.