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Entanglement distribution revealed by macroscopic observations

Johannes Kofler·Caslav Brukner
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Abstract

What can we learn about entanglement between individual particles in macroscopic samples by observing only the collective properties of the ensembles? Using only a few experimentally feasible collective properties, we establish an entanglement measure between two samples of spin-1/2 particles (as representatives of two-dimensional quantum systems). This is a tight lower bound for the average entanglement between all pairs of spins in general and is equal to the average entanglement for a certain class of systems. We compute the entanglement measures for explicit examples and show how to generalize the method to more than two samples and multi-partite entanglement.

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Johannes Kofler, Caslav Brukner. 2006-11-17. Entanglement distribution revealed by macroscopic observations. https://doi.org/10.1103/physreva.74.050304

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