Featured Research
Quantum Signatures of Chaos
A team led by Physics and Optical Science professor Poul Jessen has seen directly how the presence of classical chaos affects the behavior of a quantum system. Chaos is common in our everyday world where it affects wide range of phenomena, including electron transport, chemical reactions, neural networks, population dynamics, weather systems, and the motion of planetary bodies. Remarkably, it is still debated how chaos can emerge from quantum mechanics, which is believed to be our most complete theory of nature. This fundamental disconnect has motivated decades of theoretical study, but there remains a near-total lack of experiments that probe quantum-classical correspondence in chaotic systems. Jessen and his team have now realized a popular model system for chaos, the kicked top, using the spin of a single Cs atom. By measuring the entire spin quantum state they have made stop motion movies of the evolving quantum kicked top, and observed directly how it respects the very same boundaries between stable and chaotic motion that characterize a classical kicked top. It has recently been proposed that classical chaos will reflect itself in the degree to which the constituent parts of a quantum system become entangled. Jessen and his team has obtained the first experimental evidence for this hypothesis, by measuring the amount of entanglement between the nuclear and electron spins that make up the total spin of their Cs atom. Their data show how the spins remain largely unentangled if the classical motion is stable, and rapidly become entangled if it is chaotic.
The team published their results in the Oct. 8 issue of the journal Nature.
"Quantum Signatures of Chaos", S. Chaudhury, A. Smith, B. E. Anderson, S. Ghose, and P. S. Jessen, Nature 461, 768 (2009).
http://www.nature.com/nature/journal/v461/n7265/edsumm/e091008-04.html
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