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arXiv · 1108.2065

Coarse Graining Makes It Hard to See Micro-Macro Entanglement

Sadegh Raeisi·Pavel Sekatski·Christoph Simon
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Abstract

Observing quantum effects such as superpositions and entanglement in macroscopic systems requires not only a system that is well protected against environmental decoherence, but also sufficient measurement precision. Motivated by recent experiments, we study the effects of coarse-graining in photon number measurements on the observability of micro-macro entanglement that is created by greatly amplifying one photon from an entangled pair. We compare the results obtained for a unitary quantum cloner, which generates micro-macro entanglement, and for a measure-and-prepare cloner, which produces a separable micro-macro state. We show that the distance between the probability distributions of results for the two cloners approaches zero for a fixed moderate amount of coarse-graining. Proving the presence of micro-macro entanglement therefore becomes progressively harder as the system size increases.

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Sadegh Raeisi, Pavel Sekatski, Christoph Simon. 2012-02-19. Coarse Graining Makes It Hard to See Micro-Macro Entanglement. https://doi.org/10.1103/physrevlett.107.250401

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