Phase gate operation on a flux qubit via the readout SQUID line

ORAL

Abstract

Detuning a superconducting qubit from its rotating frame is one means to implement a phase gate operation. For superconducting flux qubits, this detuning can be realized by changing the magnetic flux threading the qubit loop, .e.g., by the mutual coupling from a nearby microwave antenna. In this work, we demonstrate an alternative approach: we implement a phase gate by pulsing a current through the readout DC SQUID. While the DC SQUID acts as a qubit flux sensor for readout, we in turn may use it as an actuator to impose the phase-gate flux shift. Using this pulsed current approach, we demonstrated Ramsey-type free-induction with more than 20 oscillation periods. We also studied the impact of the first phase gate on subsequent, sequential phase gates.

*This work is sponsored by the Department of the Air Force under contract number FA8721-05-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the author(s) and are not necessarily endorsed by the United States government.

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Authors

  • X.Y. Jin

    • Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

  • S. Gustavsson

    • Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

  • J. Bylander

    • Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

  • F. Yan

    • Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

  • F. Yoshihara

    • The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan

  • S. Nakamura

    • The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan

  • W.D. Oliver

    • MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420