Threshold error rates for the toric and planar codes

  • Authors:
  • D. S. Wang;A. G. Fowler;A. M. Stephens;L. C. L. Hollenberg

  • Affiliations:
  • Centre for Quantum Computer Technology, School of Physics, University of Melbourne, Victoria, Australia;Centre for Quantum Computer Technology, School of Physics, University of Melbourne, Victoria, Australia;Centre for Quantum Computer Technology, School of Physics, University of Melbourne, Victoria, Australia;Centre for Quantum Computer Technology, School of Physics, University of Melbourne, Victoria, Australia

  • Venue:
  • Quantum Information & Computation
  • Year:
  • 2010

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Abstract

The planar code scheme for quantum computation features a 2d array of nearest-neighborcoupled qubits yet claims a threshold error rate approaching 1% [1]. This result wasobtained for the toric code, from which the planar code is derived, and surpasses allother known codes restricted to 2d nearest-neighbor architectures by several orders ofmagnitude. We describe in detail an error correction procedure for the toric and planarcodes, which is based on polynomial-time graph matching techniques and is efficientlyimplementable as the classical feed-forward processing step in a real quantum computer.By applying one and two qubit depolarizing errors of equal probability p, we determinethe threshold error rates for the two codes (differing only in their boundary conditions)for both ideal and non-ideal syndrome extraction scenarios. We verify that the toriccode has an asymptotic threshold of pth = 15.5% under ideal syndrome extraction, and pth = 7.8×10-3 for the non-ideal case, in agreement with [1]. Simulations of the planarcode indicate that the threshold is close to that of the toric code.