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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Veröffentlicht in:Physical review letters 2012-08, Vol.109 (5), p.050507-050507, Article 050507
Hauptverfasser: Ristè, D, van Leeuwen, J G, Ku, H-S, Lehnert, K W, DiCarlo, L
Format: Artikel
Sprache:eng
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Zusammenfassung: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:0031-9007
1079-7114
DOI:10.1103/physrevlett.109.050507