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On the Qubit Routing Problem

Authors Alexander Cowtan, Silas Dilkes, Ross Duncan , Alexandre Krajenbrink, Will Simmons, Seyon Sivarajah

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Author Details

Alexander Cowtan
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom
Silas Dilkes
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom
Ross Duncan
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom
  • University of Strathclyde, 26 Richmond Street, Glasgow, G1 1XH, United Kingdom
Alexandre Krajenbrink
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom
  • Laboratoire de Physique de l'École Normale Supérieure, PSL University, CNRS, Sorbonne Universités, 24 rue Lhomond, 75231 Paris Cedex 05, France
Will Simmons
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom
Seyon Sivarajah
  • Cambridge Quantum Computing Ltd, 9a Bridge Street, Cambridge, CB2 1UB, United Kingdom


We thank Steven Herbert for many helpful conversations and encouragement.

Cite AsGet BibTex

Alexander Cowtan, Silas Dilkes, Ross Duncan, Alexandre Krajenbrink, Will Simmons, and Seyon Sivarajah. On the Qubit Routing Problem. In 14th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 135, pp. 5:1-5:32, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


We introduce a new architecture-agnostic methodology for mapping abstract quantum circuits to realistic quantum computing devices with restricted qubit connectivity, as implemented by Cambridge Quantum Computing’s t|ket> compiler. We present empirical results showing the effectiveness of this method in terms of reducing two-qubit gate depth and two-qubit gate count, compared to other implementations.

Subject Classification

ACM Subject Classification
  • Theory of computation → Quantum computation theory
  • Computer systems organization → Quantum computing
  • Hardware → Quantum computation
  • Software and its engineering → Compilers
  • Software and its engineering → Retargetable compilers
  • Quantum Computing
  • Qubit routing
  • Compilation


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