Heidelberg 2015 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 2: Quantum Effects: Entanglement and Decoherence I
Q 2.1: Vortrag
Montag, 23. März 2015, 11:30–11:45, B/gHS
Is macroscopic entanglement typical? — •Malte C. Tichy1, Chae-Yeun Park2, Minsu Kang2, Hyunseok Jeong2, and Klaus Mølmer1 — 1Deparment of Physics and Astronomy, University of Aarhus, Denmark — 2Center for Macroscopic Quantum Control, Seoul National University, Korea
Would a world without decoherence host cohorts of Schrödinger cats? Our analytical and numerical results clearly negate this question: Although most pure random quantum states in non-trivial ensembles are highly entangled, they do not feature macroscopic fluctuations in any additive local observable and therefore do not qualify as macroscopically entangled. We establish these results by formulating bounds on measures of macroscopicity in terms of geometric entanglement, which largely determine the statistics of geometric and macroscopic entanglement in random spin-chains under different ensembles of pure quantum states. Since high geometric entanglement is an obstacle to macroscopicity, generic pure states naturally feature little Schrödinger-cat-like behavior. Permutation-symmetric states, on the other hand, carry significant macroscopicity, consistent with their low geometric entanglement.