Exploiting environmental resonances to enhance qubit quality factors

Silvia Kleff, Stefan Kehrein, and Jan von Delft
Phys. Rev. B 70, 014516 – Published 29 July 2004

Abstract

We discuss dephasing times for a two-level system (including bias) coupled to a damped harmonic oscillator. This system is realized in measurements on solid-state Josephson qubits. It can be mapped to a spin-boson model with a spectral function with an approximately Lorentzian resonance. We diagonalize the model by means of infinitesimal unitary transformations (flow equations) and calculate correlation functions, dephasing rates, and qubit quality factors. We find that these depend strongly on the environmental resonance frequency Ω; in particular, quality factors can be enhanced significantly by tuning Ω to lie below the qubit frequency Δ.

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  • Received 12 March 2004

DOI:https://doi.org/10.1103/PhysRevB.70.014516

©2004 American Physical Society

Authors & Affiliations

Silvia Kleff1, Stefan Kehrein2, and Jan von Delft1

  • 1Sektion Physik and CeNS, Ludwig-Maximilians Universität, Theresienstrasse 37, 80333 München, Germany
  • 2Theoretische Physik III-EKM, Universität Augsburg, 86135 Augsburg, Germany

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Issue

Vol. 70, Iss. 1 — 1 July 2004

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