Towards a heralded eigenstate-preserving measurement of multi-qubit parity in circuit QED

Patrick Huembeli and Simon E. Nigg
Phys. Rev. A 96, 012313 – Published 11 July 2017

Abstract

Eigenstate-preserving multi-qubit parity measurements lie at the heart of stabilizer quantum error correction, which is a promising approach to mitigate the problem of decoherence in quantum computers. In this work we explore a high-fidelity, eigenstate-preserving parity readout for superconducting qubits dispersively coupled to a microwave resonator, where the parity bit is encoded in the amplitude of a coherent state of the resonator. Detecting photons emitted by the resonator via a current biased Josephson junction yields information about the parity bit. We analyze theoretically the measurement back action in the limit of a strongly coupled fast detector and show that in general such a parity measurement, while approximately quantum nondemolition is not eigenstate preserving. To remediate this shortcoming we propose a simple dynamical decoupling technique during photon detection, which greatly reduces decoherence within a given parity subspace. Furthermore, by applying a sequence of fast displacement operations interleaved with the dynamical decoupling pulses, the natural bias of this binary detector can be efficiently suppressed. Finally, we introduce the concept of a heralded parity measurement, where a detector click guarantees successful multi-qubit parity detection even for finite detection efficiency.

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  • Received 28 April 2017

DOI:https://doi.org/10.1103/PhysRevA.96.012313

©2017 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & OpticalQuantum Information, Science & Technology

Authors & Affiliations

Patrick Huembeli1,2,* and Simon E. Nigg1,†

  • 1Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
  • 2ICFO–Institut de Ciences Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Spain

  • *patrick.huembeli@icfo.eu
  • simon.nigg@unibas.ch

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Vol. 96, Iss. 1 — July 2017

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