Adiabatic Quantum Computation Is Equivalent to Standard Quantum Computation
45th Annual IEEE Symposium on Foundations of Computer Science, 2004 · paper · Computer science
Describes an efficient adiabatic simulation of any quantum algorithm, showing that adiabatic and conventional quantum computation are polynomially equivalent. The result extends to particles on a two-dimensional grid with nearest-neighbor interactions.
Checked: PDF from arxiv.org, fetched 4 Oct 2026. Page numbers are those of that PDF.
5 findings
Substance Claim 4.2 'A shape is legal if and only if it contains none of the forbidden configurations of Table 1' fails for the all-unborn (and all-dead) shape, so 'the ground space of H''_clock is the (L+1)2^n-dimensional space S' does not hold as stated.
- p. 24 Claim 4.2 and proof
A shape is legal if and only if it contains none of the forbidden configurations of Table 1.
- p. 24 Table 1
Local rules for basis state to be in S
- p. 25 Sec. 4.4.1, after definition of H''_clock
Note that the ground space of H′′ clock is the (L + 1)2n-dimensional space S.
- p. 22 after Fig. 4 reference
Notice that each shape has exactly n particles in the first or second phase.
Only the authors can say what is right here.
Judge's note: I read Table 1 on p.24 from the image. Forbidden horizontal pairs: ○↕, ○⇕, ○⊗; ○⊗, ↕⊗, ⇕⊗; ⊗○; active-active pairs. Forbidden vertical pairs: ○/⇕, ↕/⇕, ⊗/⇕; ↕/○, ↕/⇕, ↕/⊗; ○/⊗, ⊗/○; ⇕/○, ⊗/↕. Neither ○○ nor ○/○ is forbidden, and neither is ⊗⊗ or ⊗/⊗. So the all-○ and all-⊗ shapes break no rule, yet they have 0 active particles, while p.22 says every legal shape has exactly n. The proof's step 'each row must be of the form ⊗*[↕,⇕]○*' overlooks rows with no active particle. Using the definitions on p.23: H''_final = ½ΣH''_ℓ + H''_input + J·H''_clock. On all-○, every H''_ℓ term (pp.25–26) needs a ↕, ⇕, or ⊗ to act, H''_input needs ↓, and H''_clock gives 0. So all-○ is an exact eigenvector of H''(s) with eigenvalue (1−s), coming only from H''_clockinit, and that is 0 at s=1. In my own check, H''(1) has a zero-energy state outside S as well as η, so Lemma 4.7 (p.27) as stated, 'For all 0 ≤ s ≤ 1, Δ(H''(s)) = Ω(L^−3)' with a ground state of H''(1) ε-close to η, cannot follow from Lemma 3.17 as claimed. The adiabatic evolution may well survive because these states are decoupled, but only the authors can supply the missing rule or argument.
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Reference or label Lemma 3.5 is cited as "Claim 3.5" ("By Claims 3.2, 3.3, 3.5, and 3.13" on p. 16; "By Claim 3.5, the spectral gap of HS0(s) is Ω(1/L2)" on p. 17).
- p. 16 Proof of Lemma 3.12
By Claims 3.2, 3.3, 3.5, and 3.13
- p. 17 Proof of Lemma 3.12
By Claim 3.5, the spectral gap of HS0(s) is Ω(1/L2)
- p. 17 after Lemma 3.14
By Claim 3.5, the spectral gap of HS0(s) is Ω(1/L2).
- p. 17 proof of Lemma 3.11
By Claim 3.5, the spectral gap of HS0(s)
Judge's note: Page 12 labels the item 'Lemma 3.5'. There is no Claim 3.5 (the paper has Claims 3.2, 3.3, 3.4, 3.7, 3.8, 3.9, 3.13, 3.16). Claims 3.2, 3.3 and 3.13 are correctly labelled. The target is recoverable from the shared counter.
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Reference or label 'the shape changes from that shown in Fig. 4a to that shown in Fig. 4.' – the final panel letter is missing; it should be Fig. 4f (ℓ = 2nR).
- p. 22 Section 4.3, first paragraph on page
from that shown in Fig. 4a to that shown in Fig. 4.
- p. 22 Section 4.3
to that shown in Fig. 4. The locations
- p. 22 first paragraph
to that shown in Fig. 4.
Judge's note: The p.22 page image shows 'Fig. 4.' with no panel letter. Figure 4 has panels a–f, and per p.21 panel f corresponds to ℓ = 2nR = L.
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Wording H''_input := Σ_i (|↓⟩⟨↓|)_{i,1} and H''_clockinit = (I − |↑⟩⟨↑| − |↓⟩⟨↓|)_{1,1} act on column 1, but Sec. 4.2 numbers the columns 'from 0 (left) to R (right)', so the leftmost column / top-left particle is column 0.
- p. 21 Section 4.2
the columns from 0 (left) to R (right)
- p. 24 Definitions of H″input and H″clockinit
This Hamiltonian checks that none of the particles in the leftmost column are in
Judge's note: p.21 Sec. 4.2 says the columns are numbered 0..R and that columns 0 and 1 simulate the first round. On p.26, H''_{2nr+1} acts on (1,r) with r starting at 0, so γ0's active particles sit in column 0 (see also Fig. 5). On p.24 the subscripts are (i,1) and (1,1), and the text says 'The indices indicate the row and column'. The accompanying prose ('leftmost column', 'top-left particle') shows column 0 was intended. Read literally, H''_clockinit would give γ0 energy 1, which contradicts Claim 4.3. This is an index slip whose intent is clear from the prose.
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Wording 'The first term represents a Hamiltonian that acts on the two particles in positions (k, r) and (k + 1, r)' – for ℓ = 2nr+k the gate acts on rows k−1 and k, so the positions should be (k−1, r) and (k, r).
- p. 26 Downward-stage definition of H″ℓ, text after the equation
The first term represents a Hamiltonian that acts on the two particles in positions (k, r) and (k + 1, r).
- p. 26 text after H''_l for 1<k<n
acts on the two particles in positions (k, r) and (k + 1, r)
Judge's note: p.21 Sec. 4.1 says the i-th gate acts on qubits i−1 and i. The 8-dim basis listed on p.26 has the upper particle in the second phase and the lower going from the first to the second phase. In γ_{ℓ−1} that matches rows (k−1,k): rows 1..k−1 are in the second phase and rows k..n in the first. For (k,k+1), γ_{ℓ−1} would have both in the first phase. The k=n case uses the same matrix, and row n+1 does not exist there. The adjacent projector term is subscripted (k−1,r),(k,r). The sentence is the only place the positions are given, so it is an index slip with an evident fix.
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20 minor (typos and the like; most checked by the judge only)
Reference or label The known direction (adiabatic computation simulated by standard QC) is credited to "[9, 13]"/"[13,9]" on pp. 2–3 but to "[14,9]" on p. 10, where [13] and [14] are different Farhi et al. works.
- p. 2 Introduction
efficiently simulated by standard quantum computers [9, 13]
- p. 3 Section 1.1
one direction of the equivalence is already known [13,9]
- p. 3 Section 1.1
this extends the result of [9, 14]
- p. 10 Section 3, first paragraph
the other direction was shown in [14,9]
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: which of the two Farhi papers contains the simulation argument. In the reference list, [13] is Farhi et al., Science 292:472 (random NP-complete instances) and [14] is Farhi, Goldstone, Gutmann, Sipser, quant-ph/0001106. Page 2 cites [9,13], p. 3 cites [13,9], and p. 10 cites [14,9] for the same statement. The p. 3 phrase 'extends the result of [9,14]' concerns sparse Hamiltonians, but it is again attributed to [14]. The inconsistency is internal to the paper; only the authors can say which citation is meant.
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Reference or label Reference [22]: 'Number 47 in Graduate Series in Mathematics. AMS' – the AMS series is 'Graduate Studies in Mathematics'.
- p. 29 Reference [22]
Number 47 in Graduate Series in Mathematics. AMS
- p. 29 reference [22]
Graduate Series in Mathematics
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: Kitaev–Shen–Vyalyi is vol. 47 of the AMS series 'Graduate Studies in Mathematics'. The p.29 image shows 'Graduate Series in Mathematics'.
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Wording Overview says "more specifically, we show it is larger than 1/L2", but the proof of Lemma 3.5 gives only ∆ ≥ µ/(2·(6)²L²) with µ ≥ 1/2, i.e. 1/(144L²) = Ω(1/L²).
- p. 5 Section 1.3, overview
more specifically, we show it is larger than 1/L2
- p. 14 End of proof of Lemma 3.5
∆(HS0) ≥µ/(2 · (6)2L2)
- p. 14 End of proof of Lemma 3.5
∆(HS0) ≥µ/(2 · (6)2L2). Finally, notice that µ = 1 −λ ≥1
Judge's note: Page 14: 'By Theorem 2.5 ... larger than 1/(2·(6)²·L²) ... ∆(HS0) ≥ µ/(2·(6)²L²) ... µ = 1−λ ≥ 1/2'. The s<1/3 case gives 1/3. Nowhere is a bound of 1/L² itself proved. The same overview paragraph on p. 5 later says Ω(1/L²), which matches the proof. The specific constant is an overstatement.
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Wording Proof of Theorem 3.15: "T = θ(ǫ−δL7+3δ)" is claimed to satisfy Eq. (2) using ‖H′final − H′init‖ = O(L) and gap Ω(L^-3), but those inputs require T ≥ ǫ^-δ L^{7+4δ}.
- p. 20 Proof of Theorem 3.15
evolves according to H′(s) for T = θ(ǫ−δL7+3δ)
- p. 20 Proof of Theorem 3.15, running time
O(ǫ−(2+δ)L14+3δ)
- p. 20 Proof of Theorem 3.15, paragraph after Lemma 3.19
T = θ(ǫ−δL7+3δ)
- p. 20 Final running time of Theorem 3.15
O(ǫ−(16+4δ)L14+3δ)
Only the authors can say what is right here.
Judge's note: Eq. (2) on p. 8 requires T ≥ Ω(‖·‖^{1+δ}/(ǫ^δ ∆^{2+δ})). With norm O(L) (stated on p. 20) and ∆ = Ω(L^-3), the exponent is (1+δ) + 3(2+δ) = 7+4δ. The 5-local check gives 2(2+δ) = 4+2δ, which matches Claim 3.9. The later exponents (ǫ^-(2+δ)L^{14+3δ} and ǫ^-(16+4δ)L^{14+3δ}) are consistent with the printed T. Because δ > 0 is arbitrary, rescaling δ recovers the final 'for any fixed δ' bound, so Theorem 3.15 stands; the intermediate T is faulty as printed.
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Wording In the case s < 1/3, the text says "for any i ≠ 1, HS0(s)i,i > 5/6 and Σj≠i HS0(s)i,j < 1/6", but interior rows have Gerschgorin radius s, which can approach 1/3.
- p. 12 Proof of Lemma 3.5, case s < 1/3
Moreover, for any i̸ = 1, HS0(s)i,i > 5/6 and P j̸=i HS0(s)i,j < 1/6
- p. 12 case s < 1/3 in proof of Lemma 3.5
Moreover, for any i ̸= 1, HS0(s)i,i > 5/6 and P j̸=i HS0(s)i,j < 1/6.
- p. 12 case s<1/3 in proof of Lemma 3.5
HS0(s)i,i > 5/6 and P j̸=i HS0(s)i,j < 1/6
Only the authors can say what is right here.
Judge's note: Reworked from Eqs. (7)–(8) on p. 12. HS0(s) = (1−s)HS0,init + s·HS0,final. Each interior row has diagonal (1−s)·1 + s·1 = 1 and two off-diagonal entries −s/2, so Σ|a_ij| = s. Taking s = 0.3 gives radius 0.3 > 1/6, so the radius bound is false as printed (the signed sum −s < 1/6 is trivial and is not what Lemma 3.6 uses). Row 1 (radius s/2) and the last row (diagonal 1−s/2, radius s/2) are fine. Correct discs: [0, s] for row 1 and [1−s, 1+s] for interior rows, with 1−s > 2/3. So the conclusions 'all other eigenvalues > 2/3' and 'gap ≥ 1/3' still hold. Faulty step, stated result stands.
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Wording Text gives "1/L, the weight of |α(L)⟩ in |η⟩" (and the probability of ℓ = L as 1/L), but by Eq. (1), |η⟩ has L+1 equal terms, so the weight is 1/(L+1).
- p. 14 Section 3.1.3, paragraph after Claim 3.9
it is much smaller than 1/L, the weight of |α(L)⟩in |η⟩
Judge's note: Eq. (1) on p. 5 has the 1/sqrt(L+1) normalisation over ℓ = 0..L. On p. 14, 1/L appears twice as if exact. This is an approximation that does not affect the O(L) repetition argument.
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Wording Text says "then HSj,input −M is positive definite", but the difference is diag(#1s(j)−1, 0, …, 0), which is only positive semidefinite.
- p. 16 Proof of Lemma 3.12
then HSj,input −M is positive definite
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Judge's note: Page 16: HSj,input is diagonal, with top-left entry equal to the number of 1s in j and all other entries zero, and M = diag(1,0,…,0). The difference has at least L zero eigenvalues, and for j with a single 1 it is the zero matrix, so it is not positive definite. The lower bound on the ground energy needs only semidefiniteness, so the result stands.
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Wording Proof of Lemma 3.12: "the angle between the two ground spaces satisfies cos(θ) ≤ 1 − 1/L by the monotonicity property"; the bound that follows is cos θ ≤ sqrt(L/(L+1)), and 1 − 1/L fails at s = 1.
- p. 17 Proof of Lemma 3.12, first paragraph
the two ground spaces satisfies cos(θ) ≤1 −1/L by the monotonicity property
- p. 17 proof of Lemma 3.12, first paragraph
the two ground spaces satisfies cos(θ) ≤1 −1/L by the monotonicity property of the ground state
Only the authors can say what is right here.
Judge's note: M = diag(1,0,…,0) (p. 16) has ground space span{γ1..γL}. For a unit ground state α of HS0(s), cos θ = sqrt(1−α0²). Monotonicity (Claim 3.7) gives α0² ≥ 1/(L+1), so cos θ ≤ sqrt(L/(L+1)). At s = 1 every row of matrix (8) sums to 0, so the ground state is uniform and cos θ = sqrt(L/(L+1)) exactly. That exceeds 1 − 1/L for every L ≥ 1 (L = 2: 0.816 > 0.5). Using sin²(θ/2) ≥ 1/(4(L+1)) instead still gives Ω(L^-3), so Lemma 3.12 stands with a different constant.
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Wording Downward-stage H''_ℓ is written as the block matrix (0, −U_ℓ; −U_ℓ†, 0) over a basis listed with the γ_{ℓ−1}-type states (second over first phase) first; read in that order, it maps γ_{ℓ−1} to γ_ℓ by −U_ℓ†, not −U_ℓ as in H_ℓ (−U_ℓ⊗|110⟩⟨100|^c).
- p. 26 definition of H''_ℓ, ℓ=2nr+k (and cases k=n, k=1)
restriction of this Hamiltonian to the 8 dimensional space spanned by
- p. 27 Claim 4.4
For any 1 ≤ℓ≤L, H′′ S,ℓ= HS,ℓ.
Only the authors can say what is right here.
Judge's note: p.26: the basis is listed as four (upper ⇕, lower ↕) states, then four (upper ⇕, lower ⇕) states. Taking rows and columns in that order, the lower-left block −U† maps the first group (γ_{ℓ−1}) into the second (γ_ℓ). Reworking it: ⟨γ_ℓ|H|γ_{ℓ−1}⟩ = −⟨Uα|U†α⟩ = −⟨α|U†U†|α⟩. This is not −1 for a general non-Hermitian U, whereas Claim 4.4 (p.27) requires −1, consistent with the earlier H_ℓ, where the forward term is −U_ℓ⊗|110⟩⟨100|^c. The k=n and k=1 matrices have the same layout. The paper never states that the matrix rows follow the listed basis order, and if the order is reversed the matrix is correct. So this is a convention-dependent slip that only the authors can settle. The stated Claim 4.4 holds once U and U† are swapped.
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Typo Title block is dated "February 1, 2008", but the arXiv stamp on the same page reads quant-ph/0405098v2, 26 Mar 2005.
- p. 1 title block
February 1, 2008
Judge's note: The page-1 crop shows both the 2008 date and the vertical arXiv stamp '26 Mar 2005'. This is most likely a \today date regenerated when arXiv rebuilt the PDF, not an authorial claim. It is cosmetic.
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Typo Overview says "if the clock is in the state |1ℓ⟩, the computational qubits carry the result of the circuit"; only the clock state |1^L⟩ (ℓ = L) corresponds to |α(L)⟩.
- p. 5 Section 1.3, last paragraph before 'The above scheme'
if the clock is in the state |1ℓ⟩, the computational qubits carry the result of the circuit
Judge's note: The p. 5 image shows a lowercase ℓ superscript. Eq. (1) gives |α(ℓ)⟩⊗|1^ℓ0^{L−ℓ}⟩ for every ℓ, and Section 3.1.3 (p. 14) correctly says the outcome must be ℓ = L. 'Otherwise, start from scratch' confirms that one specific outcome is meant.
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Typo Theorem heading reads "Theorem 2.5 (The conductance bound [34]))" with an unmatched extra closing parenthesis.
- p. 10 Theorem 2.5 heading
Theorem 2.5 (The conductance bound [34]))
Judge's note: The crop shows one '(' and two ')'. Compare Theorem 2.1 on p. 8, where '(The Adiabatic Theorem (adapted from [29]))' has two opening parentheses and is therefore correct.
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Typo Definition "H′L := I ⊗|10⟩⟨10|c L−1,L −Uℓ⊗|1⟩⟨0|c L − U†L ⊗ ..." uses Uℓ where UL is meant.
- p. 17 Section 3.2.1, definition of H′L
H′ L := I ⊗|10⟩⟨10|c L−1,L −Uℓ⊗|1⟩⟨0|c L
- p. 17 Section 3.2.1
H′ L
- p. 17 Section 3.2.1, definition of H'_L
−Uℓ⊗|1⟩⟨0|c
- p. 17 definition of H'_L
−Uℓ ⊗|1⟩⟨0|c L
Judge's note: The p. 17 image shows subscript ℓ on the first U, but U†_L in the same line. ℓ is unbound in this boundary definition, and H'_1 correctly uses U1.
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Typo "For the boundary cases l = 1, L we define" uses a plain italic l instead of ℓ.
- p. 17 Section 3.2.1
For the boundary cases l = 1, L we define
Judge's note: The p. 17 image shows an italic 'l', while the surrounding text uses ℓ throughout.
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Typo In the proof of Lemma 3.19, δ is redefined as "δ = K²/((b−a)(J−2K)) = O(L−1ǫ2)" a few lines before δ is used again as the adiabatic-theorem exponent in "T = θ(ǫ−δL7+3δ)".
- p. 20 Proof of Lemma 3.19
is at least 1 −δ, with δ = K2 (b−a)(J−2K) = O(L−1ǫ2)
- p. 20 Proof of Theorem 3.15
T = θ(ǫ−δL7+3δ)
Judge's note: The p. 20 image shows both uses of δ within one paragraph. δ is the fixed exponent from Theorem 2.1 (p. 8). The meaning can be recovered from context, but the symbol clash is a notational ambiguity.
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Typo Asymptotic notation printed with lowercase theta: "T = θ(ǫ−δL7+3δ)" (should be Θ).
- p. 20 Proof of Theorem 3.15
T = θ(ǫ−δL7+3δ)
Judge's note: The p. 20 image shows a lowercase θ. The same symbol θ denotes the angle between ground spaces in Lemma 3.14 and the proof of Lemma 3.12 (pp. 16–17).
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Typo 'The remaining terms in each line correspond to |100⟩⟨110|^c and |100⟩⟨110|^c in H_ℓ' names the same operator twice; one should be |110⟩⟨100|^c (and the sentence lacks a final period).
- p. 25 Section 4.4.2, after the upward H″ℓ
The remaining terms in each line correspond to |100⟩⟨110|c and |100⟩⟨110|c in Hℓ
- p. 25 end of text before footnote 8
correspond to |100⟩⟨110|c and |100⟩⟨110|c in Hℓ
Judge's note: The p.25 image shows the identical term printed twice. The earlier H_ℓ (text line ~561) contains both −U_ℓ⊗|110⟩⟨100|^c and −U_ℓ†⊗|100⟩⟨110|^c.
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Typo 'where the first term shows the restriction an operator acting on the particle (1, r)' – missing 'of' ('restriction of an operator').
- p. 26 After the definition of H″2nr+1
where the first term shows the restriction an operator acting on the particle (1, r)
Judge's note: Confirmed on the p.26 page image.
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Typo Reference [2]: 'Adiabatic quantum computation is equaivalent to standard quantum computation' – misspelling of 'equivalent'.
- p. 28 Reference [2]
computation is equaivalent to standard quantum computation
- p. 28 References [2]
is equaivalent to standard quantum computation
- p. 28
computation is equaivalent to standard quantum computation, in Proc. 45th FOCS
Judge's note: Confirmed on the p.28 image crop. The paper's own title spells it 'Equivalent'.
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Typo Acknowledgments: 'Leonid Gurvitz' – the name is usually spelled 'Gurvits'.
- p. 28 Acknowledgments
Leonid Gurvitz
Only the authors can say what is right here.
Judge's note: Rests on outside knowledge: the usual published spelling of the researcher's name is 'Leonid Gurvits'. The image shows 'Gurvitz'. Transliteration variants exist, so only the authors can confirm.
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