Circuit Transformations for Quantum Architectures

Authors Andrew M. Childs , Eddie Schoute , Cem M. Unsal

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Author Details

Andrew M. Childs
  • Joint Center for Quantum Information and Computer Science, University of Maryland, USA
  • Institute for Advanced Computer Studies, University of Maryland, USA
  • Department for Computer Science, University of Maryland, USA
Eddie Schoute
  • Joint Center for Quantum Information and Computer Science, University of Maryland, USA
  • Institute for Advanced Computer Studies, University of Maryland, USA
  • Department for Computer Science, University of Maryland, USA
Cem M. Unsal
  • Department of Mathematics, University of Maryland, USA


The authors would like to thank Aniruddha Bapat for insights on the hierarchical product of graphs and suggestions for tightening the routing lower bound for these graphs. We would also like to thank Drew Risinger for helpful formative discussions.

Cite AsGet BibTex

Andrew M. Childs, Eddie Schoute, and Cem M. Unsal. Circuit Transformations for Quantum Architectures. In 14th Conference on the Theory of Quantum Computation, Communication and Cryptography (TQC 2019). Leibniz International Proceedings in Informatics (LIPIcs), Volume 135, pp. 3:1-3:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2019)


Quantum computer architectures impose restrictions on qubit interactions. We propose efficient circuit transformations that modify a given quantum circuit to fit an architecture, allowing for any initial and final mapping of circuit qubits to architecture qubits. To achieve this, we first consider the qubit movement subproblem and use the ROUTING VIA MATCHINGS framework to prove tighter bounds on parallel routing. In practice, we only need to perform partial permutations, so we generalize ROUTING VIA MATCHINGS to that setting. We give new routing procedures for common architecture graphs and for the generalized hierarchical product of graphs, which produces subgraphs of the Cartesian product. Secondly, for serial routing, we consider the TOKEN SWAPPING framework and extend a 4-approximation algorithm for general graphs to support partial permutations. We apply these routing procedures to give several circuit transformations, using various heuristic qubit placement subroutines. We implement these transformations in software and compare their performance for large quantum circuits on grid and modular architectures, identifying strategies that work well in practice.

Subject Classification

ACM Subject Classification
  • Computer systems organization → Quantum computing
  • Hardware → Quantum computation
  • Mathematics of computing → Graph theory
  • Applied computing → Physics
  • General and reference → General conference proceedings
  • Networks
  • quantum circuit
  • quantum architectures
  • circuit mapping


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