Cited by 3,325Quantum Computing Algorithms and ArchitectureQuantum Information and CryptographyQuantum many-body systems

The DOI matches its Crossref record; 35 of the 35 references it cites were found in a registry or an index.

Quantum Algorithm for Linear Systems of Equations

Open access
Harrow, Aram W., Hassidim, Avinatan, Lloyd, Seth·2009·Physical Review Letters

Abstract

Solving linear systems of equations is a common problem that arises both on its own and as a subroutine in more complex problems: given a matrix $A$ and a vector $\stackrel{\ensuremath{\rightarrow}}{b}$, find a vector $\stackrel{\ensuremath{\rightarrow}}{x}$ such that $A\stackrel{\ensuremath{\rightarrow}}{x}=\stackrel{\ensuremath{\rightarrow}}{b}$. We consider the case where one does not need to know the solution $\stackrel{\ensuremath{\rightarrow}}{x}$ itself, but rather an approximation of the expectation value of some operator associated with $\stackrel{\ensuremath{\rightarrow}}{x}$, e.g., ${\stackrel{\ensuremath{\rightarrow}}{x}}^{\ifmmode\dagger\else\textdagger\fi{}}M\stackrel{\ensuremath{\rightarrow}}{x}$ for some matrix $M$. In this case, when $A$ is sparse, $N\ifmmode\times\else\texttimes\fi{}N$ and has condition number $\ensuremath{\kappa}$, the fastest known classical algorithms can find $\stackrel{\ensuremath{\rightarrow}}{x}$ and estimate ${\stackrel{\ensuremath{\rightarrow}}{x}}^{\ifmmode\dagger\else\textdagger\fi{}}M\stackrel{\ensuremath{\rightarrow}}{x}$ in time scaling roughly as $N\sqrt{\ensuremath{\kappa}}$. Here, we exhibit a quantum algorithm for estimating ${\stackrel{\ensuremath{\rightarrow}}{x}}^{\ifmmode\dagger\else\textdagger\fi{}}M\stackrel{\ensuremath{\rightarrow}}{x}$ whose runtime is a polynomial of $\mathrm{log}(N)$ and $\ensuremath{\kappa}$. Indeed, for small values of $\ensuremath{\kappa}$ [i.e., $\mathrm{poly}\mathrm{log}(N)$], we prove (using some common complexity-theoretic assumptions) that any classical algorithm for this problem generically requires exponentially more time than our quantum algorithm.

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Research works printed but not linked: 3

  1. P. W. Shor, 1994, Proc. of the 35th FOCS
  2. P. Valiant, 2008, Proc. of the 40th Annual STOC
  3. L. Sheridan, 2009, J. Math Phys. A, 42, 185302

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Metadata

Authors
Harrow, A. W., Hassidim, A., & Lloyd, S.
Affiliations
  • University of Bristol (GB)
  • Massachusetts Institute of Technology (US)
Venue
Physical Review Letters
Published
2009-10-07
Volume
103
Issue
15
Pages
150502-150502
ISSN
  • 0031-9007 (ISSN-L)
  • 1079-7114
OpenAlex
W1492999010
Cited by
3,325
References
34
Citations by year
2026: 355 · 2025: 553 · 2024: 478 · 2023: 429 · 2022: 332 · 2021: 337 · 2020: 231 · 2019: 181 · 2018: 98 · 2017: 102 · 2016: 53 · 2015: 35 · 2014: 39 · 2013: 33 · 2012: 40
FWCI
23.75
Type
journal article
Language
en
Open access
Locations
  • Physical Review Letters (publishedVersion)
  • arXiv (Cornell University) (publishedVersion)
  • PubMed (publishedVersion)
  • DSpace@MIT (Massachusetts Institute of Technology) (submittedVersion, cc-by-nc)
  • arXiv (Cornell University)
  • PIRSA
  • Bulletin of the American Physical Society
Funders
  • W. M. Keck Foundation
  • Engineering and Physical Sciences Research Council (GR/S82169/01)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Information and Cryptography
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum many-body systems
Keywords
quantum algorithms, systems of linear equations, sparse matrices, condition number, expectation value estimation, quantum advantage

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