Initialization by measurement of a superconducting quantum bit circuit

We demonstrate initialization by joint measurement of two transmon qubits in 3D circuit quantum electrodynamics. Homodyne detection of cavity transmission is enhanced by Josephson parametric amplification to discriminate the two-qubit ground state from single-qubit excitations nondestructively and w...

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Bibliographic Details
Published inPhysical review letters Vol. 109; no. 5; p. 050507
Main Authors Ristè, D, van Leeuwen, J G, Ku, H-S, Lehnert, K W, DiCarlo, L
Format Journal Article
LanguageEnglish
Published United States 03.08.2012
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Summary:We demonstrate initialization by joint measurement of two transmon qubits in 3D circuit quantum electrodynamics. Homodyne detection of cavity transmission is enhanced by Josephson parametric amplification to discriminate the two-qubit ground state from single-qubit excitations nondestructively and with 98.1% fidelity. Measurement and postselection of a steady-state mixture with 4.7% residual excitation per qubit achieve 98.8% fidelity to the ground state, thus outperforming passive initialization.
ISSN:1079-7114
DOI:10.1103/physrevlett.109.050507