Robustness of purity of quantum channels. (30th April 2021)

• Record Type: Journal Article
• Authors: Wang, Ying; Luo, Yu; Xi, Zhengjun
• Is Part Of: Laser physics letters. Volume 18:Number 6(2021)
• Publication Date: 2021-04-30
• Subjects: purity -- quantum channels -- robustness; Lasers -- Periodicals; Physics -- Periodicals; 621.366
• DOI: 10.1088/1612-202X/abe242
• Languages: English
• ISSNs: 1612-2011

Abstract

Abstract: Quantifying purity is a basic problem in quantum information theory. When a quantum state passes through a quantum channel, its purity may be changed. In order to explore what role the quantum channel plays in this process, it is necessary to study the purity of quantum channels. In this paper, we formulate the quantum resource theory for channel purity. There are two basic elements in the quantum resource theory for channel purity: free channels and free superchannels. The free channels are completely randomizing channels which neither store nor output purity. The free superchannels are the uniformity preserving superchannels which do not generate resource channels from free ones. We also provide a method for the realization of a uniformity preserving superchannel. We quantify the purity of quantum channels by the robustness and show that the robustness of purity of a quantum channel (RPC) is a purity monotone. We obtain the efficient numerical calculation of RPC through semidefinite programming. Moreover, we find that the RPC has operational significance as the best advantage that one can obtain in the ensemble of quantum state discrimination games. As an application, we also study the RPC for some single-qubit channels.