Fault-Tolerant Quantum Computation by Anyons

Alexei Yu. Kitaev · Annals of Physics / arXiv · 2003 · physics · 10.1016/S0003-4916(02)00018-0 · record kitaev2003-anyons
tag layer · index · concepts · authors · עברית
Where this record's text came from. faceted 2026-08 by reading the locally held text (pdftext); every evidence string verified as an exact substring of that text before merging. The method vocabulary has no term for a theoretical physics model-construction paper, so I used 'theoretical-construction'. Claim type is 'method' because the deliverable is a computation scheme, but the paper also carries an existence claim (that anyons arise from a local Hamiltonian with no symmetry) that the single-valued facet cannot hold. The paper additionally criticises the existing quasi-triangular quasi-Hopf-algebra theory of anyons [10] for merely postulating anyon properties; I left that out of claim relations because it is a critique of a body of theory rather than a builds-on/extends/contradicts/replicates relation to a specific result. Discipline could equally be condensed-matter-physics. 2026-08-14, 2026-08-17 and 2026-08-25 schema-0.3 passes: every quote verified as an exact substring of the staged text and anchored at merge time; concept terms verified present; every edge endpoint an existing node.
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Tags on this paper

Every tag the record carries, each linking to every other paper in the corpus that carries it. A tag appears here whether or not its words occur in the article — the spans below are only the ones a sentence in this paper licenses. Of the 10 concept tags on this paper, 5 are grounded in a quoted sentence.
topological quantum computation anyon fault-tolerance quantum error correction braiding protected space ground state stabilizer operators anyonic excitations fault-tolerant A PHYSICAL SYSTEM IS RE-DESCRIBED AS A COMPUTER, AND THE RE-DESCRIPTION IS MARKED AS ONE: Quotation withheld, with unitary transformations performed BY MOVING THE EXCITATIONS AROUND EACH OTHER and measurements BY JOINING EXCITATIONS IN PAIRS. `Can be considered as` is a way of regarding, not an identity, and the whole paper rests on it A PROPERTY IS LOCATED IN THE PHYSICS RATHER THAN IN THE PROTOCOL: such computation is said to be FAULT-TOLERANT BY ITS PHYSICAL NATURE - so what is elsewhere achieved by a procedure is here claimed as a feature of the material. The same word, fault-tolerance, is being attached to a different kind of thing A PHYSICAL PROCESS IS RE-DESCRIBED AS AN ALGORITHM AND THE HEDGE IS LEFT IN: the spins' mutual interaction forcing a flipped spin back is said to be QUITE SIMILAR TO THE STANDARD ERROR CORRECTION PROCEDURE FOR THE REPETITION CODE, after which - WE MAY SAY THAT ERRORS ARE BEING CORRECTED AT THE PHYSICAL LEVEL. The identification is offered as a manner of speaking THE ARGUMENT PROCEEDS BY ASKING WHY AN EXISTING PRACTICE IS UNNECESSARY: classical computation CAN ALSO be performed fault-tolerantly, HOWEVER IT IS RARELY DONE IN PRACTICE BECAUSE CLASSICAL GATES ARE RELIABLE ENOUGH - and the next sentence is WHY IS IT POSSIBLE. The paper's question is generated by noticing that a technique is available and unused THE EXPLANATION IS SOUGHT IN THE EASIEST CASE FIRST AND THE CHOICE IS ANNOUNCED: LET US TRY TO UNDERSTAND THE EASIEST THING - why classical information can be stored reliably on magnetic media - before the quantum case is attempted. The order of explanation is stated rather than left implicit, and the chosen starting point is a fact about ordinary technology A THRESHOLD IS REPORTED AS THE OBSTACLE, AND ITS SIZE IS WHAT MATTERS RATHER THAN ITS EXISTENCE: an arbitrary circuit CAN be simulated with imperfect gates PROVIDED they are close to ideal up to a constant precision - and UNFORTUNATELY THE THRESHOLD VALUE IS RATHER SMALL, IT IS VERY DIFFICULT TO ACHIEVE THIS PRECISION. The theoretical solution is granted and then declared impractical by a number A PROBLEM IS DECLARED SOLVED FROM ONE STANDPOINT AND OPEN FROM ANOTHER, WITH BOTH NAMED: physical realization is A BIG CHALLENGE and decoherence is one important problem - but FROM THE PURELY THEORETICAL POINT OF VIEW, THIS PROBLEM HAS BEEN SOLVED. Solved and unsolved at once, distinguished by which standpoint the word is being used from AN EXPLICIT CAUTION AGAINST CONFLATING TWO THINGS THE SAME MATHEMATICS DESCRIBES: the local operators SHOULD NOT BE INTERPRETED AS symmetry transformations - the true symmetry transformations are a different set, and MATHEMATICALLY THEY ARE DESCRIBED BY THE SAME ALGEBRA, BUT THEIR ACTION ON PHYSICAL STATES IS DIFFERENT. One formalism, two referents, and the paper stops to say so A TERM OF ART IS CONCEDED AND THEN SET ASIDE AS NOT THE RELEVANT PROPERTY: ONE MAY SAY that these codes have QUITE POOR PARAMETERS, and WELL, THEY ARE NOT GOOD CODES IN THE SENSE OF a cited definition - HOWEVER the code corrects almost any multiple error of a stated size, SO THESE CODES WORK. The established criterion is granted, and then shown not to be the criterion that matters here quantum excitations topological unitary stabilizer degenerate anyons error nonabelian anyons degenerate state mean average of standard-error standard error theory
Method, as described: theoretical-construction

Legend

second readingalternativesan independent re-reading of a facet, recorded whether or not it agrees
relation to other workclaim_relationshow this paper stands to another: agrees, contradicts, extends, qualifies
claim typeclaim_typethe shape of the claim: existence, mechanism, method, critique, prediction, null
concept edgeconcept_edgesan asserted relation between two concepts, with the sentence asserting it
conceptconceptsan idea the paper works with, quoted where the paper uses it
content tagcontent_tagsa finding, definition, quantity, statistic or variable named in the paper
limitationlimitationswhat the paper says its evidence cannot support
mechanismmechanismshow the reported effect is said to come about
methodmethodhow the paper produced its evidence
phenomenonphenomenonthe effect or regularity under study
sensesensesa distinct use of a term, quoted where the paper fixes it
transfertransfersa method or concept carried in from another field

The paper

The full text is not reproduced here. This article is not cleared for redistribution, so the page carries the tag layer only. Its evidence sentences are withheld; the grounding status remains with each tag, and the article itself is at https://doi.org/10.1016/S0003-4916(02)00018-0. The reading view exists for the papers whose licence permits it.

Every tag on this page

alternatives 3 · claim_relations 4 · claim_type 1 · concept_edges 2 · concepts 5 · content_tags 10 · limitations 9 · mechanisms 9 · method 1 · phenomenon 1 · senses 3 · transfers 1

Relations on this page carry a quotation for the claim. Where a relation was separately evidenced — and so tested against the vocabulary for its type — the row says so; none of 2 relations here carry that mark. The rest are the tagger’s reading of the sentence quoted beside them.

This record holds no controls. A layer is empty when the tagger recorded nothing in it — which is not the same as the paper having nothing to record.

facettagfieldconf.whose words
claim_typemethod
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claim_typethe paper's words
phenomenonanyonic excitations in two-dimensional lattice spin models
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phenomenonthe paper's words
methodtheory
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also in: theory
methodthe paper's words
mechanismsmechanisms
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mechanisms[0]0.95the tagger's words
mechanismsmechanisms
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mechanisms[1]0.95the tagger's words
mechanismsmechanisms
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mechanisms[2]0.95the tagger's words
mechanismsmechanisms
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
mechanisms[3]0.95the tagger's words
mechanismsmechanisms
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
mechanisms[4]0.85the tagger's words
mechanismsmechanisms
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about this quote: The span contains 'small1;' - a footnote marker glued to the preceding word by the extraction. The quote is an exact substring and anchors correctly.
mechanisms[5]0.95the tagger's words
mechanismsmechanisms
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mechanisms[6]0.95the tagger's words
mechanismsmechanisms
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about this quote: DAMAGE SHAPE 5 INSIDE THIS SPAN, and it removes a name. The sentence reads "described by the same algebra , but their action on physical states is different" - with a space before the comma where the algebra's symbol should be. The symbol was displaced past the end of the sentence by the extraction: "...is different. D 15 a b Figure 7:". So the quote says "the same algebra [ ]" and the algebra it names is unrecoverable from the span. The tag does not name it. Found by reading; no guard sees this.
mechanisms[7]0.95the tagger's words
mechanismsmechanisms
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
mechanisms[8]0.95the tagger's words
limitationsreal quantum systems suffer decoherence and systematic errors
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what this limits: every fault-tolerance claim: DECOHERENCE AND SYSTEMATIC ERRORS IN UNITARY TRANSFORMATIONS OCCUR IN REAL QUANTUM SYSTEMS
limitations[0]the tagger's words
limitationsFor the abelian toric-code memory the author has no way to read information into or out of the protected space.
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what this limits: the abelian toric-code memory as a usable memory: UNFORTUNATELY, I DO NOT KNOW ANY WAY THIS QUANTUM INFORMATION CAN GET IN OR OUT
limitations[1]the tagger's words
limitationsThe gate set obtainable by braiding abelian anyons is not universal.
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what this limits: any universality claim for braiding abelian anyons: TOO FEW THINGS CAN BE DONE BY MOVING ABELIAN ANYONS
limitations[2]the tagger's words
limitationsThe group used for the universal-computation construction is physically implausible.
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what this limits: the universal-computation construction: (THE GROUP S5 IS QUITE UNREALISTIC FOR PHYSICAL IMPLEMENTATION)
limitations[3]the tagger's words
limitationsNo general theory underlies the constructions given.
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what this limits: the generality of the constructions: A GENERAL THEORY OF ANYONS AND TOPOLOGICAL QUANTUM ORDER IS LACKING
limitations[4]the tagger's words
limitationsThe universal-computation results are stated without full derivation, to appear elsewhere.
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what this limits: the universal-computation results as presented here: (THIS SECTION SHOULD BE CONSIDERED AS AN ABSTRACT OF RESULTS TO BE PRESENTED ELSEWHERE)
limitations[5]the tagger's words
limitationsThe number the whole fault-tolerance argument depends on is declared unknown in a footnote, with estimates three orders of magnitude apart.
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what this limits: any use of the fault-tolerance threshold cited here: a footnote states the threshold is not known and that published estimates vary across several orders of magnitude
limitations[6]1.0the tagger's words
limitationsThe case that errors can be corrected by physics rather than by procedure is made by analogy with magnetic storage, and hedged.
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what this limits: the claim that this scheme corrects errors at the physical level: the supporting argument is an analogy with spins on magnetic media, which the author introduces with 'we may say'
limitations[7]1.0the tagger's words
limitationsThe protection is degeneracy of a ground state on a surface, so the quantity protected depends on the topology chosen.
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
what this limits: the amount of protected quantum information claimed here: the protected space is the ground state of the Hamiltonian and is 4g-fold degenerate, where g is the genus of the surface the lattice is placed on
limitations[8]1.0the tagger's words
transfers1-homologies and 1-cohomologies over Z2 used to describe the protected subspace of the lattice model, so that the stored information is a topological invariant rather than a local one
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transfers[0]0.8the tagger's words
conceptsprotected space
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concepts[5]the paper's words
conceptsground state
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also in: ground state
concepts[6]the paper's words
conceptsstabilizer operators
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concepts[7]the paper's words
conceptsanyonic excitations
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concepts[8]the paper's words
conceptsfault-tolerant
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concepts[9]the paper's words
sensesfault tolerance - BY PHYSICS RATHER THAN BY PROCEDURE: Shor's construction simulates a circuit with imperfect gates given a precision threshold, whereas here the computation is said to be fault-tolerant by its physical nature, so the two uses of the phrase name a software guarantee and a property of a material
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senses[0]1.0the tagger's words
sensesthe threshold - A NUMBER THE ARGUMENT NEEDS AND NOBODY HAS: the text calls it rather small and very difficult to achieve, and the footnote says outright that it is not known, giving estimates that differ by orders of magnitude
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senses[1]1.0the tagger's words
sensesthe protected space - AS A DEGENERATE GROUND STATE: it coincides with the ground state of a Hamiltonian built from local stabilizer operators, and its size is set by the genus of the surface rather than by anything about the computation
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senses[2]1.0the tagger's words
alternativesclaim_type: method
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a second reading reaching the same value. Recorded: method — note: A BLIND second reading by the project on 2026-08-25: the record's own claim type/method/phenomenon were not looked at until every value here was written and substring-verified. Not applied - a person decides. Sampling frame: the 504 staged records carrying no alternatives block, so this never re-measures the 202. All 11 records with 130+ tags were taken as a census and 19 more spread one per discipline across 22 disciplines - the dense non-neuroscience cell is the one the 202 do not contain (inside them, 94-100% of the densest bands are neuroscience; among these 11, one is).,
alternatives.claim_type0.7the tagger's words
alternativesmethod: formal-model
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
a second reading DIFFERING from the recorded value. Recorded: theory — note: A BLIND second reading by the project on 2026-08-25: the record's own claim type/method/phenomenon were not looked at until every value here was written and substring-verified. Not applied - a person decides. Sampling frame: the 504 staged records carrying no alternatives block, so this never re-measures the 202. All 11 records with 130+ tags were taken as a census and 19 more spread one per discipline across 22 disciplines - the dense non-neuroscience cell is the one the 202 do not contain (inside them, 94-100% of the densest bands are neuroscience; among these 11, one is).,
alternatives.method0.8the tagger's words
alternativesphenomenon: decoherence and systematic gate error as the obstacle to physically realising a quantum computer
Quotation withheld — this record is not cleared for redistribution. The sentence is in the paper at the link above.
a second reading DIFFERING from the recorded value. Recorded: anyonic excitations in two-dimensional lattice spin models — note: A BLIND second reading by the project on 2026-08-25: the record's own claim type/method/phenomenon were not looked at until every value here was written and substring-verified. Not applied - a person decides. Sampling frame: the 504 staged records carrying no alternatives block, so this never re-measures the 202. All 11 records with 130+ tags were taken as a census and 19 more spread one per discipline across 22 disciplines - the dense non-neuroscience cell is the one the 202 do not contain (inside them, 94-100% of the densest bands are neuroscience; among these 11, one is).,
alternatives.phenomenon0.85the tagger's words
claim_relationsbuilds-on → quantum error-correcting codes (stabilizer codes)
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claim_relations[0]the tagger's words
claim_relationsbuilds-on → stabilizer quantum codes on lattices on the torus and other 2-D surfaces [6, 8]
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claim_relations[1]the tagger's words
claim_relationsextends → G. Castagnoli and M. Rasetti's use of one-dimensional anyons for quantum computation [14]
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claim_relations[2]the tagger's words
claim_relationsbuilds-on → Einarsson's proof that ground state degeneracy on the torus follows from the existence of anyons [19]
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claim_relations[3]the tagger's words
concept_edgesprotected space —same-as→ ground state
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strength of the relation: 1
concept_edges[0]the tagger's words
concept_edgesanyonic excitations —causes→ fault-tolerant
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strength of the relation: 1
concept_edges[1]the tagger's words
content_tags4g-fold — ground-state degeneracy of the toric-code Hamiltonian, g = genus of the surface
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content_tags.quantities[0]the tagger's words
content_tagsΔE = 2 — energy gap separating excited states (eigenvalue difference of the stabilizer operators)
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content_tags.quantities[1]the tagger's words
content_tagsA two-dimensional quantum system with anyonic excitations can serve as a quantum computer, with unitary transformations performed by moving the excitations around each other.
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content_tags.findings[0]the tagger's words
content_tagsThe ground-state degeneracy persists under local perturbation.
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content_tags.findings[1]the tagger's words
content_tagsbraiding
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also in: braiding
content_tags.variables[0]the tagger's words
content_tagsdegenerate state
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content_tags.variables[1]the tagger's words
content_tagsnonabelian anyons
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content_tags.definitions[0]the tagger's words
content_tagsbraiding
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also in: braiding
content_tags.definitions[1]the tagger's words
content_tagsmean
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also in: mean
content_tags.statistics[0]the tagger's words
content_tagsstandard-error
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content_tags.statistics[2]the tagger's words

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