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Single-shot qubit readout in circuit quantum electrodynamics

Nature Physics volume 5, pages 791795 (2009) | Download Citation

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Abstract

The future development of quantum information using superconducting circuits requires Josephson qubits1 with long coherence times combined with a high-fidelity readout. Significant progress in the control of coherence has recently been achieved using circuit quantum electrodynamics architectures2,3, where the qubit is embedded in a coplanar waveguide resonator, which both provides a well-controlled electromagnetic environment and serves as qubit readout. In particular, a new qubit design, the so-called transmon, yields reproducibly long coherence times4,5. However, a high-fidelity single-shot readout of the transmon, desirable for running simple quantum algorithms or measuring quantum correlations in multi-qubit experiments, is still lacking. Here, we demonstrate a new transmon circuit where the waveguide resonator is turned into a sample-and-hold detector—more specifically, a Josephson bifurcation amplifier6,7—which allows both fast measurement and single-shot discrimination of the qubit states. We report Rabi oscillations with a high visibility of 94%, together with dephasing and relaxation times longer than 0.5 μs. By carrying out two measurements in series, we also demonstrate that this new readout does not induce extra qubit relaxation.

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Acknowledgements

We acknowledge financial support from European projects EuroSQIP and Midas, from ANR-08-BLAN-0074-01 and from Region Ile-de-France for the nanofabrication facility at SPEC. We gratefully thank P. Senat and P. Orfila for technical support, and acknowledge useful discussions within the Quantronics group and with A. Lupascu, I. Siddiqi, M. Devoret, A. Wallraff and A. Blais.

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Affiliations

  1. Quantronics group, Service de Physique de l’État Condensé (CNRS URA 2464), DSM/IRAMIS/SPEC, CEA-Saclay, 91191 Gif-sur-Yvette cedex, France

    • François Mallet
    • , Florian R. Ong
    • , Agustin Palacios-Laloy
    • , François Nguyen
    • , Patrice Bertet
    • , Denis Vion
    •  & Daniel Esteve

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Contributions

F.M., P.B., D.V. and D.E. designed the experiment, F.R.O. fabricated the sample, F.M., F.N., A.P.-L., F.R.O. and P.B. carried out the measurements, and all of the authors contributed to the writing of the manuscript.

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Correspondence to Denis Vion.

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DOI

https://doi.org/10.1038/nphys1400

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