| speaker: | Karyn Le Hur Yale, USA Collaborators: Ph. Doucet-Beaupre (Sherbrooke), W. Hofstetter (Frankfurt), A. Kopp (Rutgers), P. Orth (Yale) |
| time: | Th., 23.08, 9:00-9:50 |
The concept of quantum entropy appears in multiple contexts, from black hole physics to quantum information theory, where it measures the entanglement of quantum states. The purpose of this talk is to study the entanglement entropy in the simplest possible model, the spin-boson model, which describes a qubit (two-level system) interacting with a collection of harmonic oscillators that models the environment responsible for decoherence and dissipation. We demonstrate that the entanglement entropy allows to make a precious unification between entanglement of the spin with its environment, decoherence, and quantum phase transitions. We derive exact analytical results which are confirmed by Numerical Renormalization Group arguments both for an Ohmic and a sub-Ohmic bosonic bath. Those unambiguously demonstrate that the entanglement entropy obeys universal scalings. We also emphasize the possibility of measuring this entanglement entropy using charge qubits subject to electromagnetic noise; such measurements would provide an empirical proof of the existence of entanglement entropy.
References: Angela Kopp and Karyn Le Hur, Phys. Rev. Lett. 98, 220401 (2007)
Karyn Le Hur, Philippe Doucet-Beaupre, Walter Hofstetter, cond-mat/0705.0957 (to be published in Phys. Rev. Lett.)