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Implementation of measurement reduction for the variational quantum eigensolver

Ralli, A; Love, PJ; Tranter, A; Coveney, PV; (2021) Implementation of measurement reduction for the variational quantum eigensolver. Physical Review Research , 3 (3) , Article 033195. 10.1103/PhysRevResearch.3.033195. Green open access

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Abstract

One limitation of the variational quantum eigensolver algorithm is the large number of measurement steps required to estimate different terms in the Hamiltonian of interest. Unitary partitioning reduces this overhead by transforming the problem Hamiltonian into one containing fewer terms. We explore two different circuit constructions of the transformation required - one built by a sequence of rotations and the other built by a linear combination of unitaries (LCU). To assess performance, we simulated chemical Hamiltonians and studied the ground states of H2 and LiH. Both implementations are successful even in the presence of noise. The sequence-of-rotations realization offers the greatest benefit to calculations, whereas the probabilistic nature of LCU reduces its effectiveness. This work also demonstrates an experimental implementation of LCU on quantum hardware.

Type: Article
Title: Implementation of measurement reduction for the variational quantum eigensolver
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/PhysRevResearch.3.033195
Publisher version: https://doi.org/10.1103/PhysRevResearch.3.033195
Language: English
Additional information: 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.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10137230
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