Understanding the effects of leakage in superconducting quantum-error-detection circuits

Joydip Ghosh, Austin G. Fowler, John M. Martinis, and Michael R. Geller
Phys. Rev. A 88, 062329 – Published 23 December 2013

Abstract

The majority of quantum-error-detection and correction protocols assume that the population in a qubit does not leak outside of its computational subspace. For many existing approaches, however, the physical qubits do possess more than two energy levels and consequently are prone to such leakage events. Analyzing the effects of leakage is therefore essential to devise optimal protocols for quantum gates, measurement, and error correction. In this article, we present a detailed study of leakage in a two-qubit superconducting stabilizer measurement circuit. We simulate the repeated ancilla-assisted measurement of a single σz operator for a data qubit, record the outcome at the end of each measurement cycle, and explore the signature of leakage events in the obtained readout statistics. An analytic model is also developed that closely approximates the results of our numerical simulations. We find that leakage leads to destructive features in the quantum-error-detection scheme, making additional hardware and software protocols necessary.

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  • Received 2 October 2013

DOI:https://doi.org/10.1103/PhysRevA.88.062329

©2013 American Physical Society

Authors & Affiliations

Joydip Ghosh1,2,*, Austin G. Fowler3,4,†, John M. Martinis3,‡, and Michael R. Geller2,§

  • 1Institute for Quantum Science and Technology, University of Calgary, Calgary, Alberta, Canada T2N 1N4
  • 2Department of Physics and Astronomy, University of Georgia, Athens, Georgia 30602, USA
  • 3Department of Physics, University of California, Santa Barbara, California 93106, USA
  • 4Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Victoria 3010, Australia

  • *ghoshj@ucalgary.ca
  • austingfowler@gmail.com
  • martinis@physics.ucsb.edu
  • §mgeller@uga.edu

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Vol. 88, Iss. 6 — December 2013

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