Bounds on the Speedup in Quantum signalling
arXiv:0910.4461 · doi:10.1103/PhysRevA.95.012331
Abstract
Given a discrete reversible dynamics, we can define a quantum dynamics, which acts on basis states like the classical one, but also allows for superpositions of them. It is a curious fact that in the quantum version, local changes in the initial state, after a single dynamical step, can sometimes can be detected much farther away than classically. Here we show that this effect is no use for generating faster signals. In a run of many steps the quantum propagation neighborhood can only increase by a constant fringe, so there is no asymptotic increase in speed.
22 pages, 9 figures
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