Cited by 2,227Quantum Computing Algorithms and ArchitectureQuantum many-body systemsQuantum Information and Cryptography

The theory of variational hybrid quantum-classical algorithms

Open access
McClean, Jarrod R, Romero, Jonathan, Babbush, Ryan, Aspuru-Guzik, Alán·2016·New Journal of Physics

Abstract

Many quantum algorithms have daunting resource requirements when compared to what is available today. To address this discrepancy, a quantum-classical hybrid optimization scheme known as 'the quantum variational eigensolver' was developed (Peruzzo et al 2014 Nat. Commun. 5 4213 ) with the philosophy that even minimal quantum resources could be made useful when used in conjunction with classical routines. In this work we extend the general theory of this algorithm and suggest algorithmic improvements for practical implementations. Specifically, we develop a variational adiabatic ansatz and explore unitary coupled cluster where we establish a connection from second order unitary coupled cluster to universal gate sets through a relaxation of exponential operator splitting. We introduce the concept of quantum variational error suppression that allows some errors to be suppressed naturally in this algorithm on a pre-threshold quantum device. Additionally, we analyze truncation and correlated sampling in Hamiltonian averaging as ways to reduce the cost of this procedure. Finally, we show how the use of modern derivative free optimization techniques can offer dramatic computational savings of up to three orders of magnitude over previously used optimization techniques.

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Registry

Crossref · 10.1088/1367-2630/18/2/023023

Cites

98 of 98 references verified0 citation errors · 0 not checkable

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  • By considering general commutations and increasing the number of gates of the circuit quadratically with n, the scaling of the number of measurements can be reduced to n^3.

    “To this end, it has been shown that by considering general commutations (and increasing the number of gates of the circuit quadratically with n ) the scaling of the number of measurements can be reduced to n 3 [213, 214, 216-219].”

    From Variational quantum algorithms (2021) · cites this paper as [218]

    Section 4.2.2, “Commuting groups and correlated sampling” (page not provided), says that grouping commuting operators can reduce the number of state preparations. It does not establish an n³ measurement scaling or say that achieving it requires a quadratic increase in circuit gates; it also cautions that correlations can affect measurement costs. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • The Variational Hamiltonian Ansatz was developed to reduce the number of parameters and accelerate convergence.

    “Motivated by adiabatic state preparation, the Variational Hamiltonian Ansatz (VHA) was developed to reduce the number of parameters and accelerate the convergence (McClean et al. , 2016; Wecker et al. , 2015).”

    From Noisy intermediate-scale quantum algorithms (2022) · cites this paper as McClean et al., 2016

    Section 3.2 (page unavailable) describes an ansatz motivated by adiabatic state preparation and says a simple linear path can use as few as one parameter. It does not say the ansatz was developed to reduce parameter count or accelerate convergence. Section 5 discusses faster convergence for particular optimization methods, not for this ansatz. (LLM, conf=0.85)

    Experimental — accuracy not yet measured
  • The electronic structure problem is one of the most prominent tasks within VQAs and was the pioneering task for VQE.

    “The electronic structure problem is one of the most prominent tasks within VQAs (see for example the reviews (Cao et al. , 2019; McArdle et al. , 2020)) and was the pioneering task for VQE (McClean et al. , 2016; Peruzzo et al. , 2014).”

    From Noisy intermediate-scale quantum algorithms (2022) · cites this paper as McClean et al. , 2016

    Section 2.2 identifies quantum chemistry and the electronic structure problem as an application of particular recent interest for VQE. The Introduction dates VQE’s development to 2014, but does not say that electronic structure was its pioneering task; it describes the original implementation without specifying its task. The broader prominence claim is cited to other reviews, not specifically to this paper. (LLM, conf=0.78)

    Experimental — accuracy not yet measured
  • Pauli strings that commute qubit-wise can be measured at the same time.

    “Pauli strings that commute qubit-wise, i.e. the Pauli operators on each qubit commute, can be measured at the same time (Kandala et al. , 2017; McClean et al. , 2016).”

    From Noisy intermediate-scale quantum algorithms (2022) · cites this paper as McClean et al., 2016

  • VQE has been proposed to find the ground state of a Hamiltonian in a manner suited for NISQ devices.

    “To this end, VQE (McClean et al. , 2016; Peruzzo et al. , 2014) has been proposed, to find the ground state of a Hamiltonian H in a manner that is suited for NISQ devices (Wecker et al. , 2015).”

    From Noisy intermediate-scale quantum algorithms (2022) · cites this paper as McClean et al. , 2016

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Cites

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Research works printed but not linked: 4

  1. Bravyi S, 2000, Ann. Phys., 298, 18
  2. Urban M, 1985, Chem. Phys., 83, 4041
  3. 10.1002/9783527626212 · DOI
  4. Holmström K, 2015, User’s Guide for TOMLAB

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Authors
McClean, J. R., Romero, J., Babbush, R., & Aspuru-Guzik, A.
Affiliations
  • Lawrence Berkeley National Laboratory (US)
  • Harvard University (US)
  • Google (United States) (US)
Corresponding author
McClean, Jarrod R
Venue
New Journal of Physics
Published
2016-02-04
Volume
18
Issue
2
Pages
023023
ISSN
1367-2630 (ISSN-L)
OpenAlex
W2257937122
Cited by
2,227
References
93
Citations by year
2026: 219 · 2025: 353 · 2024: 306 · 2023: 321 · 2022: 310 · 2021: 337 · 2020: 203 · 2019: 99 · 2018: 50 · 2017: 18 · 2016: 9
FWCI
48.22
Type
journal article
Language
en
Open access
Locations
  • New Journal of Physics (publishedVersion, cc-by)
  • arXiv (Cornell University) (submittedVersion)
  • Digital Access to Scholarship at Harvard (DASH) (Harvard University) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
  • OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • Army Research Office (W911NF-15-1-0256)
  • Air Force Office of Scientific Research (FA9550-12-1-0046)
  • Office of Naval Research Global (N00014-16-1-2008)
  • Defense Security Science Engineering Fellowship (N00014-16-1-2008)
  • Lawrence Berkeley National Laboratory (Luis W. Alvarez Fellowship in Compu)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum many-body systems
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Information and Cryptography
Keywords
hybrid quantum-classical algorithms, unitary coupled cluster, universal gate set, truncation, correlated sampling, derivative-free optimization

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