Dynamics of dispersive single qubit read-out in circuit quantum electrodynamics

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 transmi...

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Bibliographic Details
Published in:arXiv.org 2009-11
Main Authors: Bianchetti, R, Filipp, S, Baur, M, Fink, J M, Göppl, M, Leek, P J, Steffen, L, Blais, A, Wallraff, A
Format: Article
Language:English
Subjects:
Differential equations
Dispersion
Electromagnetic fields
Operators (mathematics)
Quantum electrodynamics
Quantum theory
Qubits (quantum computing)
Resonators
Transmission lines
Online Access:Get full text
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Summary: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.
ISSN:2331-8422
DOI:10.48550/arxiv.0907.2549