2011/11/15 by Davide Girolami, Gerardo Adesso · 2 citations
Computer Science · Mathematics · Physics and Astronomy · #Observable #Physics #Quantum #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum correlation #Quantum discord #Quantum entanglement #Quantum mechanics #Qubit #Qutrit #Separable state #cond-mat.stat-mech #math-ph #math.MP #quant-ph
paper · pdf · doi:10.1103/physreva.84.052110
published as Phys. Rev. A A 84, 052110 (2011) · 10 pages, 4 figures
arxiv created 2011/11/15 · openalex publication_date 2011/11/15 · arxiv updated 2011/11/17 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Composite quantum systems can be in generic states characterized not only by entanglement but also by more general quantum correlations. The interplay between these two signatures of nonclassicality is still not completely understood. In this work we investigate this issue, focusing on computable and observable measures of such correlations: entanglement is quantified by the negativity N, while general quantum correlations are measured by the (normalized) geometric quantum discord DG. For two-qubit systems, we find that the geometric discord reduces to the squared negativity on pure states, while the relationship DG\ensuremath≥N2 holds for arbitrary mixed states. The latter result is rigorously extended to pure, Werner, and isotropic states of two-qudit systems for arbitrary d, and numerical evidence of its validity for arbitrary states of a qubit and a qutrit is provided as well. Our results establish an interesting hierarchy, which we conjecture to be universal, between two relevant and experimentally friendly nonclassicality indicators. This ties in with the intuition that general quantum correlations should at least contain and in general exceed entanglement on mixed states of composite quantum systems.