Cited by 8,830Quantum Computing Algorithms and ArchitectureQuantum Information and CryptographyQuantum Mechanics and Applications

A fast quantum mechanical algorithm for database search

Open access
Grover, Lov K.·1996·Proceedings of the twenty-eighth annual ACM symposium on Theory of computing - STOC '96

Abstract

An unsorted database contains N records, of which just one satisfies a particular property.The problem is to identify that one record.Any classical algorithm, deterministic or probabilistic, will clearly take O (N) steps since on the average it will have to examine a large fraction of the N records.Quantum mechanical systems can do several operations simultaneously due to their wave like properties.This paper gives an O ( JN) step quantum mechanical algorithm for identifying that record.It is within a constant factor of the fastest possible quantum mechanical algorithm.

Integrity signals

Registry

Crossref · 10.1145/237814.237866

Cites

24 of 24 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 8 cited sources checked · 0 supported · 0 flagged

  • Findingnone given

    The paper gives an O(√N) step quantum mechanical algorithm for identifying the unique record satisfying a particular property in an unsorted database of N records.

    “This paper gives an O ( JN) step quantum mechanical algorithm for identifying that record.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: There is a unique state that satisfies the condition C(S)=1.
    • The authors state this as an assumption: For any state S, the condition C(S) can be evaluated in unit time.
  • Findingreasoning

    After applying the diffusion transform to a state with one amplitude k and N-1 amplitudes l, if k is negative and l positive with |k| < l/√N, then both resulting amplitudes are positive.

    “Corollary 3.1-Let the state vector be as followsfor any one state the amplitude is k, for each of the remaining (N-1) states the amplitude is 1.Let k and 1 be real numbers (in general the amplitudes can be complex).Let k be negative and 1 be positive such that ~< ~N.Then after applying the diffusion transform both k and 1are positive numbers.”
    Quote in the paperSubstantial claim
  • Findingreasoning

    The system is a valid quantum mechanical system.

    “First, it is proved that the system is a valid quantum mechanical system (theorems 1 & 2)”
    Quote in the paperSubstantial claim
  • Findingnone given

    The algorithm does not use any knowledge about the problem.

    “As mentioned in the introduction, the algorithm of this paper does not use any Imowledge about the problem.”
    Quote in the paperSubstantial claim
  • Findingnone given

    The diffusion transform D is unitary.

    “Theorem 1-The matix D is unitary.”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 8
  • May combine two claims. 4
  • The quote only partly states this claim. 1
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    If an experiment with success probability ε is repeated K times, the probability that the outcome does not happen even once is ≤ e^{-K}.

    “Theorem 5-Let the probability of a particular outcome in an experiment be &.Then if the experiment be repeated ~times, the probability that the outcome does not happen even once is less than or equal to e-K.”
    Quote in the paperNot a substantial claim
  • May combine two claims.

    Findingreasoning

    After steps (a) and (b) of the algorithm, the change in k is lower bounded by a positive amount, and l remains positive.

    “The change in k ( Ak) after steps (a) and (b) of the algorithm is lower bounded by Ak>~.Also after steps (a) and (b), 1>0.2fi”
    Quote in the paperSubstantial claim
  • The quote only partly states this claim.

    Findingreasoning

    There exists M less than √N such that in M repetitions of the loop, k becomes 1/√2.

    “Using this it immediately follows that there exists a number M less than EN, such that in M repetitions of the loop in step (ii), k wifl become ~.”
    Quote in the paperSubstantial claim
  • May combine two claims.

    Premisereasoning

    The most efficient classical algorithm for unsorted database search examines items one by one and needs to look at an average of N/2 items before finding the desired one.

    “The most efficient classical algorithm for this is to examine the items in the database one by one.”
    Quote in the paperSubstantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Very recent results have shown the existence of quantum mechanical error correcting codes which enable transmission of data even in the presence of noise.

    “Very recent results [Shor95] have shown the existence of quantum mechanical error corr~ting cod~which enable transmission of data even in the presence of noise”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [Shor95]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    Shor's algorithm is the only known algorithm that solves the problem in O(log N) steps.

    “This algorithm, by cleverly making use of some features of the structure of the problem, is the only known algorithm that solves the problem in O (logIV) steps.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisenone given

    The phase of the amplitude does not have an analog in classical probabilistic algorithms.

    “The phase does not have an analog in classical probabilistic algorithms.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    In quantum mechanics, the complete description of the system requires the amplitudes over all states; probabilities alone are not enough.

    “This illustrates the point that, in quantum mechanics, the complete description of the system requires the amplitudes over all states, just the probabilities is not enough.”
    Quote in the paperNot a substantial claim
  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Shor's primality testing algorithm for a number N can be viewed as a search of the (N-1) numbers smaller than N to see if any is a factor of N.

    “For example Shor's primality testing algorithm [Shor94] for a number N can be viewed as a search of the (N-l) numbers smaller than N to see if any of them is a factor of N.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [Shor94]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    There is a scheme by which it is possible to modify any algorithm that solves an NP-search problem with a unique solution and use it to solve an NP-search problem in general.

    “There is also a scheme discussed in [VV86] by which it is possible to modify any algorithm that solves an NPsearch problem with a unique solution and use it to solve an NP-search problem in general.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [VV86]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The Fourier transformation operation is one of the things that makes quantum mechanical algorithms more powerful than classical algorithms and forms the basis for most significant quantum mechanical algorithms.

    “This operation is one of the things that makes quantum mechanical algorithms more powerful than classical algorithms and forms the basis for most significant quantum mechanical algorithms.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [DJ92]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

11 of 11
  • The authors state this as an assumption.

    There is a unique state that satisfies the condition C(S)=1.

    “Let there be a unique state, say Sv, that satisfies the condition C(SV) = 1, whereas for all other states S, C(S) = 0”
    “The algorithm as discussed here assumes a unique state that satisfies the desired condition.”
  • The authors state this as an assumption.

    For any state S, the condition C(S) can be evaluated in unit time.

    “(assume that for any state S, the condition C(S) can be evaluated in unit time)”
  • The paper relies on this without support.

    There does not exist any sorting on the database that would aid selection of the desired item.

    “However, there does not exist any sorting on the database that would aid its selection.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Grover's algorithm offers a quadratic speed-up for brute-force key search, effectively halving the security margin of symmetric ciphers.

    “Symmetric cryptography remains comparatively resilient, yet Grover's algorithm offers a quadratic speed-up for brute-force key search, effectively halving the security margin of symmetric ciphers [13].”

    From Harvest-Now, Decrypt-Later: A Temporal Cybersecurity Risk in the Quantum Transition (2025) · cites this paper as [13]

    The Abstract reports O(N) steps for classical search and an O(√N)-step quantum algorithm, supporting the quadratic speed-up for unstructured search. The paper does not discuss brute-force cipher-key search or assess the security margin of symmetric ciphers; applying its result to those claims goes beyond what this source states. (LLM, conf=0.85)

    Experimental — accuracy not yet measured
  • Grover's algorithm can facilitate a quantum birthday attack to find collisions, thereby necessitating an output of larger size for hash functions.

    “Similarly, for hash functions, Grover's algorithm [185] can facilitate quantum birthday attack to find collision, thereby necessitating an output of larger size.”

    From Zero Trust Architecture (ZTA): A Comprehensive Survey (2022) · cites this paper as [185]

    The Abstract describes Grover’s quantum search algorithm and its square-root speedup for finding a record in an unsorted database. The paper does not discuss hash functions, quantum birthday attacks, collisions, or the need for larger hash outputs, so it does not support the claimed application. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • Grover's algorithm gives a quadratic advantage for mining blocks in proof-of-work consensus protocols.

    “Similarly, Grover’s algorithm concedes a quadratic advantage for mining blocks in certain consensus protocols such as proof of work.”

    From Quantum-resistance in blockchain networks (2023) · cites this paper as [71]

    The Abstract (page not listed) reports an O(√N) quantum search algorithm versus O(N) classical search, supporting the quadratic advantage. It does not address block mining or proof-of-work consensus, so the application to those protocols is not established by this paper. (LLM, conf=0.88)

    Experimental — accuracy not yet measured
  • Quantum computers will be able to find proof-of-work nonces quadratically faster using Grover's algorithm.

    “Quantum computers will be able to find these nonces quadratically faster using Grover’s algorithm71.”

    From Quantum-resistance in blockchain networks (2023) · cites this paper as [71]

    The Abstract reports an O(√N) quantum search algorithm versus O(N) classical search, and the discussion on p. 114 says the algorithm can be modified when multiple states satisfy the condition. That supports the claimed quadratic search speedup, but our copy does not address proof-of-work nonces specifically or establish the claim about future computers finding them. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • This HNDL model is realistic given the falling cost of storage, the rise of large-scale surveillance infrastructures, and the expected disruption of quantum algorithms such as Shor's and Grover's.

    “This model is realistic given the falling cost of storage, the rise of large-scale surveillance infrastructures, and the expected disruption of quantum algorithms such as Shor's and Grover's [1,2,13].”

    From Harvest-Now, Decrypt-Later: A Temporal Cybersecurity Risk in the Quantum Transition (2025) · cites this paper as [13]

    The Abstract describes Grover’s quantum search algorithm as taking O(√N) steps where classical search takes O(N), and the Introduction mentions Shor’s efficient factoring algorithm. These passages support the claim that the algorithms offer substantial computational advances, but they do not address their expected disruption of encryption or the realism of the HNDL model. Falling storage costs and surveillance infrastructure are not claims this citation specifically supports. (LLM, conf=0.84)

    Experimental — accuracy not yet measured

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. [9]9. R. Penrose, Shadows of the mind,. Oxford University Press, 1994, pp. 348- 388.
  2. [14]14. Yao93J A. Yao, Quantum circuit complexip, Proceedings 34th Annual Symposium on Foundations of Computer Science (FOCS), 1993, pp. 352-361.

Cited by

Sorted by citations

Authors
Grover, L. K.
Affiliations
AT&T (United States) (US)
Corresponding author
Grover, Lov K.
Venue
Proceedings of the twenty-eighth annual ACM symposium on Theory of computing - STOC '96
Publisher
ACM Press
Published
1996
Pages
212-219
OpenAlex
W2084652510
Cited by
8,830
References
24
Citations by year
2026: 664 · 2025: 1066 · 2024: 896 · 2023: 841 · 2022: 674 · 2021: 655 · 2020: 529 · 2019: 423 · 2018: 288 · 2017: 283 · 2016: 219 · 2015: 221 · 2014: 184 · 2013: 161 · 2012: 158
FWCI
36.24
Type
conference paper
Language
en
Open access
Locations
  • ACM Symposium on Theory of Computing (STOC) (publishedVersion)
  • CERN Document Server (European Organization for Nuclear Research) (submittedVersion)
Topics
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Computing Algorithms and Architecture
  • Physical Sciences › Computer Science › Artificial Intelligence › Quantum Information and Cryptography
  • Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Quantum Mechanics and Applications
Keywords
quantum search, unsorted database search, Grover's algorithm, quantum algorithms, time complexity, quantum parallelism, lower bounds

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