• Open Access

Fault-Tolerant Qubit from a Constant Number of Components

Kianna Wan, Soonwon Choi, Isaac H. Kim, Noah Shutty, and Patrick Hayden
PRX Quantum 2, 040345 – Published 2 December 2021

Abstract

With gate error rates in multiple technologies now below the threshold required for fault-tolerant quantum computation, the major remaining obstacle to useful quantum computation is scaling, a challenge greatly amplified by the huge overhead imposed by quantum error correction itself. We propose a fault-tolerant quantum computing scheme that can nonetheless be assembled from a small number of experimental components, potentially dramatically reducing the engineering challenges associated with building a large-scale fault-tolerant quantum computer. Our scheme has a threshold of 0.39% for depolarizing noise, assuming that memory errors are negligible. In the presence of memory errors, the logical error rate decays exponentially with T/τ, where T is the memory coherence time and τ is the timescale for elementary gates. Our approach is based on a novel procedure for fault-tolerantly preparing three-dimensional cluster states using a single actively controlled qubit and a pair of delay lines. Although a circuit-level error may propagate to a high-weight error, the effect of this error on the prepared state is always equivalent to that of a constant-weight error. We describe how the requisite gates can be implemented using existing technologies in quantum photonic and phononic systems. With continued improvements in only a few components, we expect these systems to be promising candidates for demonstrating fault-tolerant quantum computation with a comparatively modest experimental effort.

  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
  • Figure
10 More
  • Received 19 December 2020
  • Revised 17 September 2021
  • Accepted 5 November 2021

DOI:https://doi.org/10.1103/PRXQuantum.2.040345

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

Kianna Wan1, Soonwon Choi2, Isaac H. Kim3,4,*, Noah Shutty1, and Patrick Hayden1

  • 1Stanford Institute for Theoretical Physics, Stanford University, Stanford, California 94305, USA
  • 2Department of Physics, University of California Berkeley, Berkeley, California 94720, USA
  • 3Department of Computer Science, UC Davis, Davis, California 95616, USA
  • 4School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia

  • *ikekim@ucdavis.edu

Popular Summary

One of the important scientific goals of our time is to build a fault-tolerant quantum computer. These are quantum computers that are effectively error-free, and therefore capable of running large-scale quantum algorithms with important practical ramifications in a variety of disciplines, such as chemistry and materials science.

While the theory of fault-tolerant quantum computation asserts that building such a device is possible in principle, the engineering effort needed can be enormous. To suppress the error, quantum information must be spread across many physical qubits, with estimates on the number of physical qubits ranging from hundreds to thousands. In the existing paradigm for fault-tolerant quantum computation, all of these qubits must be individually and simultaneously controlled, a task that is not impossible but challenging.

Motivated by this difficulty, we propose a new approach to fault-tolerant quantum computation that can dramatically reduce such engineering efforts. In this paper, we show that a logical qubit with extremely low logical error rates can be built using only a handful of experimental components, namely, a photon emitter, two delay lines, two routers, and a single-photon detector. This is a significant improvement over the existing paradigm, which would have required hundreds if not thousands of components to build a logical qubit of similar quality. Thus, our proposal paves ways towards building a practical fault-tolerant quantum computer, with much smaller engineering overhead than what was previously anticipated.

Key Image

Article Text

Click to Expand

References

Click to Expand
Issue

Vol. 2, Iss. 4 — December - December 2021

Reuse & Permissions
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from PRX Quantum

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

×

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×