Dynamics of dispersive single-qubit readout in circuit quantum electrodynamics

R. Bianchetti, S. Filipp, M. Baur, J. M. Fink, M. Göppl, P. J. Leek, L. Steffen, A. Blais, and A. Wallraff
Phys. Rev. A 80, 043840 – Published 30 October 2009

Abstract

The quantum state of a superconducting qubit nonresonantly coupled to a transmission line resonator can be determined by measuring the quadrature amplitudes of an electromagnetic field transmitted through the resonator. We present experiments in which we analyze in detail the dynamics of the transmitted field as a function of the measurement frequency for both weak continuous and pulsed measurements. We find excellent agreement between our data and calculations based on a set of Bloch-type differential equations for the cavity field derived from the dispersive Jaynes-Cummings Hamiltonian including dissipation. We show that the measured system response can be used to construct a measurement operator from which the qubit population can be inferred accurately. Such a measurement operator can be used in tomographic methods to reconstruct single and multiqubit states in ensemble-averaged measurements.

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  • Received 15 July 2009

DOI:https://doi.org/10.1103/PhysRevA.80.043840

©2009 American Physical Society

Authors & Affiliations

R. Bianchetti1, S. Filipp1, M. Baur1, J. M. Fink1, M. Göppl1, P. J. Leek1, L. Steffen1, A. Blais2, and A. Wallraff1

  • 1Department of Physics, ETH Zurich, CH-8093 Zürich, Switzerland
  • 2Département de Physique, Université de Sherbrooke, Sherbrooke, Canada J1K 2R1

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Vol. 80, Iss. 4 — October 2009

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