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Average-Case Verification of the Quantum Fourier Transform Enables Worst-Case Phase Estimation

Quantum Physics · Submitted 21 Sep 2021

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim In this paper we show that, in fact, we only need to have good average-case performance of the QFT to achieve good worst-case performance for key tasks -- phase estimation, period finding and amplitude estimation.

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arXiv ID2109.10215 (version 3)
Pith IDFCCEB6EQ, Pith's permanent record of this paper and its review
CitationCWI, Noah Linden (University of Bristol), Ronald de Wolf (QuSoft, University of Amsterdam). "Average-Case Verification of the Quantum Fourier Transform Enables Worst-Case Phase Estimation." arXiv:2109.10215 (2021). https://pith.science/paper/FCCEB6EQ
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The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

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Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 4,940 input tokens.

What the abstract itself states, as probabilities: claims first 0.06 · states limitation 0.23 · human participants 0.01 · controlled comparison 0.03 · randomized assignment 0.01 · states quantitative result 0.10 · compares with prior results 0.16 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v3. Results and the main claim are underlined; .

The quantum Fourier transform (QFT) is a key primitive for quantum computing that is typically used as a subroutine within a larger computation, for instance for phase estimation. As such, we may have little control over the state that is input to the QFT. Thus, in implementing a good QFT, we may imagine that it needs to perform well on arbitrary input states. Verifying this worst-case correct behaviour of a QFT-implementation would be exponentially hard (in the number of qubits) in general, raising the concern that this verification would be impossible in practice on any useful-sized system. In this paper we show that, in fact, we only need to have good average-case performance of the QFT to achieve good worst-case performance for key tasks -- phase estimation, period finding and amplitude estimation. Further we give a very efficient procedure to verify this required average-case behaviour of the QFT.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#sentencerolethe authors' own workstates the main conclusionstrength
s0 The quantum Fourier transform (QFT) is a key primitive for quantum computing that is typically used as a subroutine within a larger computation, for instance for phase estimation. background 1.00 0.04 0.02 asserted 0.98
s1 As such, we may have little control over the state that is input to the QFT. background 0.99 0.09 0.02 hedged possibility 1.00
s2 Thus, in implementing a good QFT, we may imagine that it needs to perform well on arbitrary input states. background 0.97 0.06 0.02 hedged possibility 0.94
s3 Verifying this worst-case correct behaviour of a QFT-implementation would be exponentially hard (in the number of qubits) in general, raising the concern that this verification would be impossible in practice on any useful-sized system. background 0.61 0.08 0.03 asserted 0.82
s4 In this paper we show that, in fact, we only need to have good average-case performance of the QFT to achieve good worst-case performance for key tasks -- phase estimation, period finding and amplitude estimation. result 0.64 0.94 0.94 asserted 1.00
s5 Further we give a very efficient procedure to verify this required average-case behaviour of the QFT. contribution 0.59 0.95 0.11 asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.87 · evidence from proof or derivation 0.97.

What was examined, and what was not

sources read
  • arXiv listing abstract v3
not examined
  • full text
  • figures and tables
  • references and citing sentences
  • relations to other papers
levels run
  • P abstract
not run
  • S sections
  • T body sentences
  • C citations
  • R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

The paper
Original abstract

The quantum Fourier transform (QFT) is a key primitive for quantum computing that is typically used as a subroutine within a larger computation, for instance for phase estimation. As such, we may have little control over the state that is input to the QFT. Thus, in implementing a good QFT, we may imagine that it needs to perform well on arbitrary input states. Verifying this worst-case correct behaviour of a QFT-implementation would be exponentially hard (in the number of qubits) in general, raising the concern that this verification would be impossible in practice on any useful-sized system. In this paper we show that, in fact, we only need to have good average-case performance of the QFT to achieve good worst-case performance for key tasks -- phase estimation, period finding and amplitude estimation. Further we give a very efficient procedure to verify this required average-case behaviour of the QFT.

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What this paper does with the arXiv papers it cites

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

What it cites · 5 sentences without a confident label

Cites as background 7 papers
  • This means that efficient verification of worst-case correctness typically requires additional assumptions, ranging from restrictions on the class of circuits one is verifying (for instance Clifford circuits [ref] ) to cryptographic assumptions (as in Mahadev's approach [ref] , which also assumes the computation starts with a fixed initial state).

    Lightweight Detection of a Small Number of Large Errors in a Quantum Circuit · Verification of quantum circuits · 0.85

  • This means that efficient verification of worst-case correctness typically requires additional assumptions, ranging from restrictions on the class of circuits one is verifying (for instance Clifford circuits [ref] ) to cryptographic assumptions (as in Mahadev's approach [ref] , which also assumes the computation starts with a fixed initial state).

    Direct Fidelity Estimation from Few Pauli Measurements · Verification of quantum circuits · 0.85

  • This means that efficient verification of worst-case correctness typically requires additional assumptions, ranging from restrictions on the class of circuits one is verifying (for instance Clifford circuits [ref] ) to cryptographic assumptions (as in Mahadev's approach [ref] , which also assumes the computation starts with a fixed initial state).

    Classical Verification of Quantum Computations · Verification of quantum circuits · 0.85

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