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SUMMARY:Quantum correlations versus entanglement in composite systems - Ge
 rardo Adesso (University of Nottingham)
DTSTART:20120308T141500Z
DTEND:20120308T151500Z
UID:TALK36271@talks.cam.ac.uk
CONTACT:Paul Skrzypczyk
DESCRIPTION:The correlations of multipartite quantum states can have noncl
 assical features other than entanglement. After giving a brief overview of
  the subject\, we focus on the issue of establishing a hierarchy between m
 easures of entanglement and compatible measures of general quantum correla
 tions. We analyze a family of measures of general quantum correlations for
  composite systems\, defined in terms of the bipartite entanglement necess
 arily created between systems and apparatuses during local measurements. F
 or every entanglement monotone $E$\, this operational correspondence provi
 des a different measure $Q_E$ of quantum correlations. Examples of such me
 asures are the relative entropy of quantumness\, the quantum deficit\, and
  the negativity of quantumness. In general\, we prove that any so defined 
 quantum correlation measure is always greater than (or equal to) the corre
 sponding entanglement between the subsystems\, $Q_E \\ge E$\, for arbitrar
 y states of composite quantum systems. In this respect\, quantum correlati
 ons truly go beyond entanglement. We then discuss the extent up to which t
 hey can exist without entanglement\, namely whether there are upper bounds
  on some measure of quantum correlations for separable states of a given d
 imension. Addressing this largely open question can be very relevant for t
 hose applications for which general quantum correlations\, and not entangl
 ement\, provide the essential resources.
LOCATION:MR4\, Centre for Mathematical Sciences
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