Dissipative LandauZener transitions of a qubit: Bathspecific and universal behavior
Abstract
We study LandauZener transitions in a qubit coupled to a bath at zero temperature. A general formula that is applicable to models with a nondegenerate ground state is derived. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubitbath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard LandauZener probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure offdiagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fastpulse readout of superconducting phase qubits.
 Authors:
 Department of Physics, Graduate School of Science, University of Tokyo, Tokyo 1130033 (Japan)
 (Japan)
 Institut fuer Physik, Universitaet Augsburg, Universitaetsstrasse 1, D86135 Augsburg (Germany)
 Department of Mathematical Science, Graduate School of Engineering, Osaka Prefecture University, Sakai 5998531 (Japan)
 Publication Date:
 OSTI Identifier:
 20951520
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 21; Other Information: DOI: 10.1103/PhysRevB.75.214308; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; COUPLING; FLUCTUATIONS; GROUND STATES; PROBABILITY; QUANTUM COMPUTERS; QUANTUM ELECTRODYNAMICS; QUBITS; SPIN; TEMPERATURE ZERO K; TUNNEL EFFECT
Citation Formats
Saito, Keiji, Department of Physics, Graduate School of Science, 2 CREST, JST, 418 Honcho Kawaguchi, Saitama 3320012, Wubs, Martijn, Kohler, Sigmund, Haenggi, Peter, and Kayanuma, Yosuke. Dissipative LandauZener transitions of a qubit: Bathspecific and universal behavior. United States: N. p., 2007.
Web. doi:10.1103/PHYSREVB.75.214308.
Saito, Keiji, Department of Physics, Graduate School of Science, 2 CREST, JST, 418 Honcho Kawaguchi, Saitama 3320012, Wubs, Martijn, Kohler, Sigmund, Haenggi, Peter, & Kayanuma, Yosuke. Dissipative LandauZener transitions of a qubit: Bathspecific and universal behavior. United States. doi:10.1103/PHYSREVB.75.214308.
Saito, Keiji, Department of Physics, Graduate School of Science, 2 CREST, JST, 418 Honcho Kawaguchi, Saitama 3320012, Wubs, Martijn, Kohler, Sigmund, Haenggi, Peter, and Kayanuma, Yosuke. Fri .
"Dissipative LandauZener transitions of a qubit: Bathspecific and universal behavior". United States.
doi:10.1103/PHYSREVB.75.214308.
@article{osti_20951520,
title = {Dissipative LandauZener transitions of a qubit: Bathspecific and universal behavior},
author = {Saito, Keiji and Department of Physics, Graduate School of Science, 2 CREST, JST, 418 Honcho Kawaguchi, Saitama 3320012 and Wubs, Martijn and Kohler, Sigmund and Haenggi, Peter and Kayanuma, Yosuke},
abstractNote = {We study LandauZener transitions in a qubit coupled to a bath at zero temperature. A general formula that is applicable to models with a nondegenerate ground state is derived. We calculate exact transition probabilities for a qubit coupled to either a bosonic or a spin bath. The nature of the baths and the qubitbath coupling is reflected in the transition probabilities. For diagonal coupling, when the bath causes energy fluctuations of the diabatic qubit states but no transitions between them, the transition probability coincides with the standard LandauZener probability of an isolated qubit. This result is universal as it does not depend on the specific type of bath. For pure offdiagonal coupling, by contrast, the tunneling probability is sensitive to the coupling strength. We discuss the relevance of our results for experiments on molecular nanomagnets, in circuit QED, and for the fastpulse readout of superconducting phase qubits.},
doi = {10.1103/PHYSREVB.75.214308},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 21,
volume = 75,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
}

We calculate the exact LandauZener transition probabilities for a qubit with an 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 diagonal coupling, the bath does not influence the transition probability, whatever the speed of the LandauZener sweep. It is proposed to use LandauZener transitions to determine both the reorganization energy and the integrated spectral density of the bath. Possible applications include circuit QED and molecular nanomagnets.

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