Quantum speed limit for physical processes

Abstract

The evaluation of the minimal evolution time between two distinguishable states of a system is important for assessing the maximal speed of quantum computers and communication channels. Lower bounds for this minimal time have been proposed for unitary dynamics. Here we show that it is possible to extend this concept to nonunitary processes, using an attainable lower bound that is connected to the quantum Fisher information for time estimation. This result is used to delimit the minimal evolution time for typical noisy channels.Comment: results unchanged; new in this version: greater focus on geometrical interpretation of results, added references, improvements in style, comments on exclusion window left mainly for the supplemental material; main article: 7 pages (including references), 2 figures; supplemental material: 5 pages, 4 figure