Gauging a quantum heat bath with dissipative Landau-Zener transitions

TL;DR

This paper derives exact Landau-Zener transition probabilities for a qubit coupled to a bath, revealing entanglement effects and proposing a method to characterize quantum heat baths.

Contribution

It provides an exact solution for Landau-Zener transitions with arbitrary bath coupling and introduces a novel approach to gauge bath properties via these transitions.

Findings

Exact transition probabilities for arbitrary linear bath coupling.

Entanglement between qubit and bath in the final state.

Bath does not affect transition probability in diagonal coupling case.

Abstract

We calculate the exact Landau-Zener transitions probabilities for a qubit with arbitrary linear coupling to a bath at zero temperature. The final quantum state exhibits a peculiar entanglement between the qubit and the bath. In the special case of a diagonal coupling, the bath does not influence the transition probability, whatever the speed of the Landau-Zener sweep. It is proposed to use Landau-Zener transitions to determine both the reorganization energy and the integrated spectral density of the bath. Possible applications include circuit QED and molecular nanomagnets.