Regensburg 2010 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 11: Quantum Dynamics, Decoherence, and Quantum Information II
DY 11.4: Vortrag
Dienstag, 23. März 2010, 15:00–15:15, H38
Creation and destruction of entanglement by a nonequilibrium environment — •Max Ludwig1, Klemens Hammerer2, and Florian Marquardt1 — 1Department of Physics, Center for NanoScience, and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, Munich, Germany — 2Institute for Theoretical Physics, University of Innsbruck, and Institute for Quantum Optics and Quantum Communication, Austrian Academy of Sciences, Innsbruck, Austria
Recent experiments try to cool nanomechanical resonators to the ground state by coupling them to nonequilibrium environments that originate either from electrons or cooper pairs in single electron transistors, or from photons inside an optical cavity. The ultimate goal of these experiments is the observation of quantum effects on macroscopic objects such as entanglement between coupled oscillators. This raises the general question of how nonequilibrium environments affect entanglement.
Here we show that there is an optimal dissipation strength for which the entanglement between two coupled oscillators is maximized. Below this value the cooling mechanism is too weak to overcome the influence of the thermal environment. Above this value, the dissipation via the nonequilibrium bath destroys entanglement. Our results are established with the help of a general framework of exact quantum Langevin equations valid for arbitrary bath spectra, in and out of equilibrium. We point out why the commonly employed Lindblad approach fails to give even a qualitatively correct picture.