Cited by 719Quantum Computing Algorithms and ArchitectureQuantum many-body systemsQuantum Information and Cryptography

Progress towards practical quantum variational algorithms

Open access
Wecker, Dave, Hastings, Matthew B., Troyer, Matthias·2015·Physical Review A

Abstract

The preparation of quantum states using short quantum circuits is one of the most promising near-term applications of small quantum computers, especially if the circuit is short enough and the fidelity of gates high enough that it can be executed without quantum error correction. Such quantum state preparation can be used in variational approaches, optimizing parameters in the circuit to minimize the energy of the constructed quantum state for a given problem Hamiltonian. For this purpose we propose a simple-to-implement class of quantum states motivated by adiabatic state preparation. We test its accuracy and determine the required circuit depth for a Hubbard model on ladders with up to 12 sites (24 spin orbitals), and for small molecules. We find that this ansatz converges faster than previously proposed schemes based on unitary coupled clusters. While the required number of measurements is astronomically large for quantum chemistry applications to molecules, applying the variational approach to the Hubbard model (and related models) is found to be far less demanding and potentially practical on small quantum computers. We also discuss another application of quantum state preparation using short quantum circuits, to prepare trial ground states of models faster than using adiabatic state preparation.

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Crossref · 10.1103/physreva.92.042303

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15 of 15 references verified0 citation errors · 0 not checkable

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  • Several quantum machine learning algorithms based on parameterized quantum circuits have demonstrated superior performance and computational abilities compared to conventional algorithms.

    “Several QML algorithms based on PQC have been proposed [21–27], demonstrating superior performance and computational abilities compared to conventional algorithms [28–31].”

    From Medical image diagnosis based on adaptive Hybrid Quantum CNN (2023) · cites this paper as [21]

    The opening summary (p. 1) reports that a parameterized quantum-circuit ansatz converged faster than earlier unitary-coupled-cluster schemes. The Discussion (p. 10) describes outperforming classical computers as a prospect, not a demonstrated result. The paper therefore does not establish the cited claim that several quantum machine-learning algorithms have demonstrated superior performance over conventional algorithms. (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 Wecker et al., 2015

    The Introduction (pp. 1–2) describes a Hamiltonian variational ansatz inspired by adiabatic state preparation, with few parameters and a shorter sequence of rotations. The faster convergence reported in “Optimization with Exact Energies” (p. 4) is specifically for an annealed optimization procedure using that ansatz, not a general property established for the ansatz itself. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • 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 Wecker et al. , 2015

  • The AQC model is computationally equivalent to the gate model, meaning algorithms written in either model can be translated to the other without prohibitive computational overhead.

    “The AQC model has been shown to be computationally equivalent to the gate model 62 , meaning that algorithms written in either model can be translated to ones in the other model without incurring prohibitive computational overhead.”

    From Quantum Chemistry in the Age of Quantum Computing (2019) · cites this paper as [62]

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Research works printed but not linked: 2

  1. [13]D. Jaksch and P. Zoller, Annals of Physics, 315 52 (2005).
  2. [14]M. J. D. Powell, Computer Journal 7 , 155 (1964).

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Authors
Wecker, D., Hastings, M. B., & Troyer, M.
Affiliations
  • Microsoft (United States) (US)
  • ETH Zurich (CH)
Venue
Physical Review A
Published
2015-10-02
Volume
92
Issue
4
ISSN
  • 0556-2791 (ISSN-L)
  • 1050-2947
  • 1094-1622
OpenAlex
W2254754114
Cited by
716
References
15
Citations by year
2026: 48 · 2025: 108 · 2024: 101 · 2023: 97 · 2022: 100 · 2021: 110 · 2020: 69 · 2019: 40 · 2018: 21 · 2017: 11 · 2016: 11
FWCI
14.03
Type
journal article
Language
en
Open access
Locations
  • Physical Review A (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • arXiv (Cornell University)
Funders
  • Microsoft Research
  • National Science Foundation (PHY-1066293)
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
quantum state preparation, adiabatic state preparation, variational ansatz, Hubbard model, unitary coupled cluster, quantum chemistry, circuit depth, NISQ devices

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