When are correlations quantum? -- Verification and quantification of entanglement by simple measurements

Abstract

The verification and quantification of experimentally created entanglement by simple measurements, especially between distant particles, is an important basic task in quantum processing. When composite systems are subjected to local measurements the measurement data will exhibit correlations, whether these systems are classical or quantum. Therefore, the observation of correlations in the classical measurement record does not automatically imply the presence of quantum correlations in the system under investigation. In this work we explore the question of when correlations, or other measurement data, are sufficient to guarantee the existence of a certain amount of quantum correlations in the system and when additional information, such as the degree of purity of the system, is needed to do so. Various measurement settings are discussed, both numerically and analytically. Exact results and lower bounds on the least entanglement consistent with the observations are presented. The approach is suitable both for the bi-partite and the multi-partite setting.

10 pages and 4 figures, material and references added

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Cited by in corpus (14)

• Entanglement detection
• Entanglement in continuous variable systems: Recent advances and current perspectives
• Quantum Many-Body Phenomena in Coupled Cavity Arrays
• Effective spin systems in coupled micro-cavities
• Measuring Measurement: Theory and Practice
• Unifying several separability conditions using the covariance matrix criterion
• On experimental procedures for entanglement verification
• Entanglement dynamics in chains of qubits with noise and disorder
• Further results on entanglement detection and quantification from the correlation matrix criterion
• Optimal estimation of entanglement
• Lower bounds on entanglement measures from incomplete information
• Probing a composite spin-boson environment
• Experimental entanglement verification and quantification via uncertainty relations
• Geometrically induced singular behavior of entanglement