2021/04/29 by Ming-Jing Zhao, Ming‐Jing Zhao, Teng Ma +1
Computer Science · Mathematics · Physics and Astronomy · #Coherence (philosophical gambling strategy) #Mathematics #Physics #Quantum #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum mechanics #Statistical physics #quant-ph
paper · pdf · doi:10.1103/physreva.103.042428
published as Phys. Rev. A 103, 042428 (2021)
openalex publication_date 2021/04/29 · arxiv created 2021/05/06 · arxiv updated 2021/05/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We study the average quantum coherence over the pure state decompositions of a mixed quantum state. An upper bound of the average quantum coherence is provided, and sufficient conditions for the saturation of the upper bound are shown. These sufficient conditions always hold for two- and three-dimensional systems. This provides a tool to estimate the average coherence experimentally by measuring only the diagonal elements, which remarkably requires less measurements compared with state tomography. We then describe the pure state decompositions of the qubit state in the Bloch sphere geometrically. For any given qubit state, the optimal pure state decomposition achieving the maximal average quantum coherence as well as three other pure state decompositions are shown in the Bloch sphere. The order relations among their average quantum coherence are invariant for any coherence measure. The results presented in this paper are universal and suitable for all coherence measures.