Duvenhage, Rocco de Villiers2022-10-052022-10-052021-09-07Duvenhage, R . 2021, 'Optimal quantum channels', Physical Review A, vol. 104, no. 3, art. 032604, pp. 1-8, doi : 10.1103/PhysRevA.104.032604.1050-2947 (print)1094-1622 (online)10.1103/PhysRevA.104.032604https://repository.up.ac.za/handle/2263/87525A method to optimize the cost of a quantum channel is developed. The goal is to determine the cheapest channel that produces prescribed output states for a given set of input states. This is essentially a quantum version of optimal transport. To attach a clear conceptual meaning to the cost, channels are viewed in terms of what we call elementary transitions, which are analogous to point-to-point transitions between classical systems. The role of entanglement in optimization of cost is emphasized. We also show how our approach can be applied to theoretically search for channels performing a prescribed set of tasks on the states of a system, while otherwise disturbing the state as little as possible.en© 2021 American Physical SocietyQuantum channelsOptimization of costArticle