paper

Universal and measurable entanglement entropy in the spin-boson model

arXiv:cond-mat/0612095 · doi:10.1103/PhysRevLett.98.220401

Abstract

We study the entanglement between a qubit and its environment from the spin-boson model with Ohmic dissipation. Through a mapping to the anisotropic Kondo model, we derive the entropy of entanglement of the spin , where is the dissipation strength, is the tunneling amplitude between qubit states, and is the level asymmetry. For and , we show that the Kondo energy scale controls the entanglement between the qubit and the bosonic environment ( is a high-energy cutoff). For , the disentanglement proceeds as ; for , vanishes as , up to a logarithmic correction. For a given , the maximum entanglement occurs at a value of which lies in the crossover regime . We emphasize the possibility of measuring this entanglement using charge qubits subject to electromagnetic noise.

4 pages and 4 figures; updated version to appear in Physical Review Letters

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