Nonequilibrium transfer and decoherence in quantum impurity problems

TL;DR

This paper derives exact relations for nonequilibrium transfer rates in quantum impurity models, revealing how tunneling and decoherence behave across different regimes and providing bounds for quantum coherence damping.

Contribution

It establishes exact relations between transfer rates in impurity models and derives closed-form expressions for the biased spin-boson model, linking tunneling crossover and decoherence.

Findings

Exact transfer rate relations for boundary sine-Gordon and Kondo models.

Closed-form transfer rate expressions in the biased spin-boson model.

Lower bound for decoherence damping as a function of bias and dissipation.

Abstract

Using detailed balance and scaling properties of integrals that appear in the Coulomb gas reformulation of quantum impurity problems, we establish exact relations between the nonequilibrium transfer rates of the boundary sine-Gordon and the anisotropic Kondo model at zero temperature. Combining these results with findings from the thermodynamic Bethe ansatz, we derive exact closed form expressions for the transfer rate in the biased spin-boson model in the scaling limit. They illustrate how the crossover from weak to strong tunneling takes place. Using a conjectured correspondence between the transfer and the decoherence rate, we also determine the exact lower bound for damping of the coherent oscillation as a function of bias and dissipation strength in this paradigmic model for NMR and superposition of macroscopically distinct states (qubits).