Valley and orbital state spectroscopy of a Si/SiGe triple quantum dot

ORAL

Abstract

Valley and orbital states have important consequences for silicon based qubits, and a thorough understanding of their interaction in the few electron regime is crucial in forming robust qubits. While many spin-based qubits operate best with large valley and orbital splittings, valley qubits such as the quantum dot hybrid qubit [1] utilize the valley degree of freedom for its logical states. Here we present measurements of valley and orbital energies using excited state spectroscopy in a triple quantum dot fabricated using an Al-AlxO1-x-Al overlapping gate design. Valley splitting is shown to vary as a function of electron occupancy in the N=1 to N=4 regime between 35 and 70 µeV. We observe that higher lying orbital levels have a larger valley splitting, and we present tight binding simulations consistent with this observation. The spatial dependence of the valley splitting in a linear array of quantum dots is also investigated. Finally, we observe anomalously low orbital splittings of 200-400 µeV that could have potential applications to new readout mechanisms for certain silicon based qubits.

[1] Dohun Kim, et. al. npj Quantum Inf., 1:15004, 2015.

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Presenters

  • John Dodson

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

Authors

  • John Dodson

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Joelle Baer

    University of Wisconsin - Madison

  • Jose Carlos Abadillo-Uriel

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Nathan Holman

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Trevor Knapp

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Brandur Thorgrimsson

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Evan R MacQuarrie

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Samuel Neyens

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Thomas McJunkin

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Ryan Foote

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Lisa Edge

    HRL Laboratories, LLC

  • Mark G Friesen

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Susan Coppersmith

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin-Madison, University of Wisconsin - Madison

  • Mark Alan Eriksson

    Department of Physics, University of Wisconsin-Madison, University of Wisconsin-Madison, University of Wisconsin - Madison