Aaronson–Ambainis conjecture: bounded low-degree polynomials have a variable of influence poly(Var/d)
A crisp analytic conjecture with partial results (special cases, exponential-in-degree bound, restriction results) and one retracted proof, so a path is visible but not obvious. Application value is minimal. Leverage is moderate: it decides how structure-free quantum speed-ups can be.
The problem
Must every bounded, low-degree function of many yes/no inputs that genuinely varies have one input that matters noticeably?
- 1Bounded varying function of many bits
- 2Low degree: only small combinations
- 3Conjecture: some bit matters a fair amount
- 4True ⇒ quantum queries only polynomially better
- 5Only exponentially weak version proved
Setup. Let be a multilinear polynomial of degree at most , written in the Fourier basis as . Its variance is . The of coordinate is , which measures how much coordinate affects .
Path to understanding
foundations → problemThe research entries this problem rests on, in the order to read them. Each links to its explainer.
- Start with
- Step 2
- Step 3
- Quantum algorithmsAlgorithm · host
- Then
- Aaronson–Ambainis conjecture: bounded low-degree polynomials have a variable of influence poly(Var/d)The problem
State of the art
Known. The Dinur–Friedgut–Kindler–O'Donnell theorem (STOC 2006) gives a maximum influence that is polynomial in but exponentially small in . Montanaro (2012) proved the conjecture for block-multilinear forms whose coefficients all have equal magnitude, and Bansal, Sinha and de Wolf (2022) for completely bounded block-multilinear forms. A 2020 claimed proof by Keller and Klein contained an error and was withdrawn. Bhattacharya (arXiv:2402.13952, ITCS 2025) proved that the conjecture holds for a non-negligible fraction of random restrictions when the variance is not too small, using the junta-approximation theorem of Filmus, Hatami, Keller and Lifshitz. Girish, Mittal, Nehoran and Raz (arXiv:2609.35327, September 2026, preprint) show that the analogues of the conjecture for biased product distributions and for Hamming slices are each equivalent to the original.
Related but distinct. The October 2026 OpenAI release includes an unrefereed AI-generated claim that the worst-case relation for total Boolean functions is tight; that concerns worst-case query complexity of total functions, not the average-case simulation the conjecture is about.
Realistic applications
If true, quantum query speed-ups over classical algorithms for total Boolean functions on average inputs are at most polynomial, which clarifies where exponential quantum speed-ups can live (structured problems, not unstructured search over total functions). The conjecture also bears on bounded-depth quantum circuits and on pseudo-random function testing. There are no engineering applications.
What counts as solved
A proof of for a universal constant for all bounded degree- multilinear , or an explicit family of bounded polynomials with . Any improvement of the DFKO bound to would be partial progress.
How it gets verified
Expert reviewOnly expert review of the argument is possible today.
The statement is an influence bound for bounded low-degree multilinear polynomials, max_i Inf_i[f] >= (Var[f]/d)^C, or an explicit counterexample family. Mathlib has no Boolean-function analysis library, so it cannot be Lean-checked yet. Experts review the proof, and a counterexample could be partly screened numerically on small cases.
Claims under verification
+ add a claimWhere the work is
Fourier-analytic proof; small-case computation only for examples.
Bottlenecks
ranked by votes- #1TheoryExponential-to-polynomial gap in the degree
The best general bound loses a factor exponential in ; known proofs go through induction on degree or junta approximation, both of which incur exponential dependence.
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Connected problems
Progress
- Sep 28, 2026Distributional variants equivalent (preprint)source
Girish, Mittal, Nehoran and Raz proved that biased-product and slice versions are equivalent to the uniform conjecture. Not refereed.
- Feb 21, 2024Random restrictionssource
Bhattacharya proved the conjecture for a non-negligible fraction of random restrictions (ITCS 2025).
- Nov 5, 2009Conjecture stated with quantum consequencessource
Aaronson and Ambainis posed the conjecture and showed it implies classical simulation of quantum query algorithms on most inputs.
- May 21, 2006Exponential-in-degree boundsource
Dinur, Friedgut, Kindler and O'Donnell proved an influence lower bound exponentially small in the degree (STOC 2006).