Local Information as an Essential Factor for Quantum Entanglement

• Published in: Entropy (Basel, Switzerland) Vol. 23; no. 6; p. 728
• Main Author: Su, Zhaofeng
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 08.06.2021; MDPI
• Subjects: Correlation analysis; Data processing; Decomposition; Eigenvalues; Entangled states; geometric parameters; Inequality; Mathematical analysis; Norms; Numerical analysis; Parameters; Quantum entanglement; Quantum mechanics; Quantum phenomena; Quantum physics; Qubits (quantum computing); two-qubit system
• ISSN: 1099-4300; 1099-4300
• DOI: 10.3390/e23060728

Quantum entanglement is not only a fundamental concept in quantum mechanics but also a special resource for many important quantum information processing tasks. An intuitive way to understand quantum entanglement is to analyze its geometric parameters which include local parameters and correlation parameters. The correlation parameters have been extensively studied while the role of local parameters have not been drawn attention. In this paper, we investigate the question how local parameters of a two-qubit system affect quantum entanglement in both quantitative and qualitative perspective. Firstly, we find that the concurrence, a measure of quantum entanglement, of a general two-qubit state is bounded by the norms of local vectors and correlations matrix. Then, we derive a sufficient condition for a two-qubit being separable in perspective of local parameters. Finally, we find that different local parameters could make a state with fixed correlation matrix separable, entangled or even more qualitatively entangled than the one with vanished local parameters.