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Influence of low-frequency noise on macroscopic quantum tunneling in superconducting circuits

Mathias Duckheim and Joachim Ankerhold
Phys. Rev. B 71, 134501 – Published 4 April 2005
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  • INTRODUCTION
  • FREE-ENERGY METHOD FOR TUNNELING RATES
  • SLUGGISH BATH
  • SLUGGISH BATH AND 1∕f DAMPING
  • QUANTRONIUM QUBIT
  • CONCLUSIONS
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    The influence of low- to moderate-frequency environments on macroscopic quantum tunneling (MQT) in superconducting circuits is studied within the ImF approach to evaluate tunneling rates. Particular attention is paid to two model environments, namely, a pure sluggish bath and a sluggish bath with additional 1∕f noise. General findings are applied to Zener flip tunneling, a MQT phenomenon recently predicted and observed in a superconducting circuit implementing a quantum bit.

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    • Received 11 November 2004

    DOI:https://doi.org/10.1103/PhysRevB.71.134501

    ©2005 American Physical Society

    Authors & Affiliations

    Mathias Duckheim1,*,† and Joachim Ankerhold1,2

    • 1Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Straße 3, D-79104 Freiburg, Germany
    • 2Service de Physique de l’Etat Condensé, DSM/DRECAM, CEA Saclay, 91191 Gif-sur-Yvette, France

    • *Electronic address: mathias.duckheim@unibas.ch
    • †Present address: Department of Physics and Astronomy, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland.

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    Issue

    Vol. 71, Iss. 13 — 1 April 2005

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    Images

    • Figure 1
      Figure 1
      MQT rates in the presence of a sluggish bath vs temperature for various values of the coupling constant j=0.0, 0.1, 0.3, 0.5 (from top to bottom). Shown are results according to (26) (solid line), numerical results (dashed line), and perturbative results according to (29) (dotted line).Reuse & Permissions
    • Figure 2
      Figure 2
      Probability for escape vs bias current for a Josephson junction with dimensionless barrier height v=3 and various values of the coupling to a sluggish bath j=0.0 (solid line), 0.1 (dashed line), and 0.3 (dotted line).Reuse & Permissions
    • Figure 3
      Figure 3
      Rate enhancement due to a sluggish bath with 1∕f noise vs temperature. The couplings constants are j̃=κ̃=0.05 (solid line), 0.1 (dotted line), 0.2 (dashed line), and ω+∕ω0=1∕50. The inset shows the suppression only because of dynamical modes (j̃=0), but with the same values for κ̃.Reuse & Permissions
    • Figure 4
      Figure 4
      Diabatic potential surfaces V+ (dashed line) and V− (solid line) outside (left) and inside (right) the range where Zener flip tunneling occurs.Reuse & Permissions
    • Figure 5
      Figure 5
      Ordinary bounce (thin line) and flip-bounce trajectory (thick line). The inset displays the inverted diabatic potentials (V+, thin line, V−, thick line) intersecting at qc.Reuse & Permissions
    • Figure 6
      Figure 6
      Rate enhancement due to Zener flip tunneling temperature in presence of a bath with a 1∕f spectrum and various values for the coupling constant (from top to bottom) j̃=κ̃=0.0 (solid line), 0.1, 0.2, 0.3 (dashed line).Reuse & Permissions
    • Figure 7
      Figure 7
      Probability to escape vs external bias current for the quantronium circuit and in the parameter range where Zener flip tunneling occurs. The solid line is the result including Zener flips, whereas the dashed one is generated using the standard MQT rate for j̃=0.1,κ̃=0.Reuse & Permissions
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