A Google quantum researcher has publicly criticized the Bitcoin QDay Prize, arguing the competition rewarded the wrong thing and risked confusing the debate around quantum threats to cryptography. In a blog post published April 25, Craig Gidney, a research scientist on Google’s quantum computing team, said he declined to enter the contest last year because he believed its design had “two showstopping issues” that made a meaningful result unlikely. His critique was directed at the contest framework and the winning submission’s interpretation, not at the broader idea that quantum computing could eventually threaten widely used cryptography.
Google researcher says QDay Prize missed key flaws
Gidney wrote that the first flaw was technical and fundamental: current hardware is not yet capable of running cryptographically relevant versions of Shor’s algorithm without quantum error correction. “The first showstopper is that Shor’s algorithm requires error correction. Current quantum computers experience on the order of one error per thousand gates, but cryptographically relevant instances of Shor’s algorithm require billions of gates,” he wrote. “The only known way to cross this chasm is quantum error correction.” According to Gidney, that means a contest focused on present-day hardware would inevitably measure non-error-corrected circuits with very different scaling behavior from the systems that would matter for real-world key breaking.
He said he warned organizers of a second issue before the competition ended: small Shor-style demonstrations can appear successful largely by chance. In his account, that makes judging difficult because outputs from a weak or effectively irrelevant quantum process can still look correct on toy-sized problems. “For the near future, the contribution of luck is going to massively outweigh any legitimate contribution of the quantum computer,” Gidney wrote in the message he says he sent when declining to participate. “So I suspect the winner in 2026 will be whoever did the best job at obfuscating how they made themselves unavoidably lucky. You’re going to find yourself in a philosophical debate, with 100K$ on the line, over where exactly the line for a quantum computer ‘really’ breaking a key is.”
In the same post, Gidney said the contest arrived at the very outcome he had feared. He wrote that after the winner was selected, GitHub user @yuvadm, identified in the post as Yuval Adam, tested the submission by swapping the quantum calls for random calls and found the outputs “indistinguishable” from the reported quantum results. Gidney added that he reviewed the submission’s code and said “the circuit construction looks fine,” citing its use of an ELDPC circuit described in Roetteler et al. 2017. But he argued that this was precisely the problem: a technically coherent circuit can still produce the “right answer for the wrong reason” if the benchmark is vulnerable to accidental success.
Gidney argues winning method measured luck, not progress
Project 11, according to Gidney’s post, summarized the competition result on X as: “Researcher breaks 15-bit ECC key on publicly accessible quantum hardware in a 512x jump from the previous public demonstration.” Gidney disputed the significance of that framing. He said the prior demonstration used as the baseline had “the exact same problem,” and argued that boosting the result as a major leap risked overstating what had actually been shown on hardware.
He also addressed a defense from one of the contest runners, again as summarized in his post. According to Gidney, the organizer argued that the winning submission followed the rules, was reviewed by “three independent physics experts” against a predefined rubric, and still represented progress because it demonstrated a variant of Shor’s algorithm for ECDLP on real, publicly accessible hardware without custom silicon. Gidney rejected that reasoning. “If the rules accepted this submission, the rules were written wrong. The quantum computer should actually be contributing something of value in order for a submission to be accepted,” he wrote. “This submission would have yielded the same result if it were run in 1996 instead of 2026. Therefore this submission is not a measure of quantum progress.”
Even so, Gidney’s post did not dismiss the broader security issue. He wrote that “there are legitimate concerns that quantum computers could become cryptographically relevant before the end of the decade,” and cited ongoing post-quantum migration efforts by companies including Google and Cloudflare as evidence that the risk is taken seriously. His argument was narrower: that poorly designed public milestones can muddy, rather than clarify, where the technology actually stands. “The competition failed in the way it was predictably going to fail,” he wrote in his closing remarks. “Save what credibility you have left and call a duck a duck. Take it on the chin, and be more careful next time.”
For crypto market participants and infrastructure operators, Gidney’s criticism matters less as a dispute over one prize and more as a reminder that quantum security claims require careful scrutiny. The source material does not include a direct response from Project 11 beyond the defense quoted by Gidney, so readers should treat this as a reported account of his objections rather than a fully adjudicated record. Still, the post adds a detailed, technically grounded critique to a debate that is likely to remain central as post-quantum transitions accelerate across the industry.
AI Transparency Note: This article was prepared with the assistance of an AI system based on the sources listed and was reviewed, edited, and approved by a human editor before publication. All quotes, data points, and factual claims are intended to be grounded in the cited source material; however, errors cannot be ruled out entirely.
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