Optimization of variational-quantum-eigensolver measurement by partitioning Pauli operators using multiqubit Clifford gates on noisy intermediate-scale quantum hardware

Andrew Jena, Scott N. Genin, and Michele Mosca
Phys. Rev. A 106, 042443 – Published 27 October 2022

Abstract

Measuring the expectation value of Pauli operators on prepared quantum states is a fundamental task in a multitude of quantum algorithms. Simultaneously measuring sets of Pauli operators allows for fewer measurements and an overall speedup of the measurement process. Using results from coloring random graphs, we give evidence for an upper bound on the expected minimum number of simultaneously measurable parts necessary to partition a set of Pauli operators. By expanding our gate set to allow multiqubit Clifford gates before measurement, we were able to cut down the number of measurements considerably compared to previous approaches. We conjecture that this improvement is, in general, linear with respect to the lengths of the Pauli operators. We conclude by demonstrating the feasibility of this approach by implementing the variational quantum eigensolver on the Aspen-4-4Q-A quantum processor unit. In doing so, we calculate the ground-state energies of H2 using fewer measurements than is possible with single-qubit gates with no statistically significant difference in accuracy.

  • Figure
  • Received 10 May 2022
  • Accepted 23 May 2022

DOI:https://doi.org/10.1103/PhysRevA.106.042443

©2022 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsQuantum Information, Science & Technology

Authors & Affiliations

Andrew Jena*

  • Department of Combinatorics and Optimization, University of Waterloo, Waterloo, N2L 3G1 Ontario, Canada and Institute for Quantum Computing, University of Waterloo, Waterloo, N2L 3G1 Ontario, Canada

Scott N. Genin

  • OTI Lumionics Inc., 3415 American Drive, Unit 1, Mississauga, L4V 1T4 Ontario, Canada

Michele Mosca

  • Department of Combinatorics and Optimization, University of Waterloo, Waterloo, N2L 3G1 Ontario, Canada; Institute for Quantum Computing, University of Waterloo, Waterloo, N2L 3G1 Ontario, Canada; and Perimeter Institute for Theoretical Physics, Waterloo, N2L 2Y5 Ontario, Canada

  • *ajjena@uwaterloo.ca
  • scott.genin@otilumionics.com
  • michele.mosca@uwaterloo.ca

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Issue

Vol. 106, Iss. 4 — October 2022

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