Research scientist on Google's quantum team, working on reducing the cost of quantum error correction.
Useful tools I've made:
- Quirk: https://algassert.com/quirk
- Stim: https://github.com/quantumlib/stim
- Crumble: https://algassert.com/crumble
Craig Gidney
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I would bet against Q day by 2030, but I wouldn't bet against it at 10:1 odds. ~10% risk is unacceptably high here, so I'm very in favor of transitioning to quantum-safe cryptography by 2029: blog.google/innovation-a...
Yes this means I 90% expect to be made fun of in 2030. Oh well.
Whoops, I missed that they have multiple shots. The gate overhead is ~5600x not 256x.
And, of course, if you're in charge of some security thing that's vulnerable to quantum attacks, you should be *assuming progress*. The strategy "we'll start our 3 year plan when it looks 4 years away" is just guaranteeing an "oh shit" moment when progress subtracts 2 years.
The cost of holding assumptions constant is they go stale. In 2012, demanding 1e-3 noise was audacious. Now it's conservative. Locality? The mechanisms for long-range connections are multiplying and improving. Frankly, if you assume *progress*, 100k qubits starts looking high.
Made a video tutorial of using crumble to create a quantum error correction circuit: youtu.be/SnpLSvyyEx8
While I was attending APS March Meeting, I appeared in the 632nm podcast. The recording is available on youtube: www.youtube.com/watch?v=lnHg...
Never been on a podcast before, and no doubt that shows, but it was fun.
I've been asked several times to comment on arxiv.org/abs/2602.11457, which claims to reduce the qubit cost of factoring by 10x.
My take is that they demand a *lot* more qubit connectivity for that number. Your mileage depends entirely on how plausible you find those demands.
This might be unappreciated outside the field, but it's easy to juice numbers by demanding more from hardware. It's a common type of paper (e.g. arxiv.org/abs/2103.06159 and arxiv.org/abs/2302.06639). To avoid this confounder. I've tried to hold my assumptions constant over time.
Chevignard et al show residues also reduce the qubit cost of quantum attacks on elliptic curves: eprint.iacr.org/2026/280
The space savings is less dramatic than for factoring (1.6x instead of 6x), and they again pay a big gate count penalty (256x), but very interesting.
The slides from my talk "how to eat magic states" at APS 2026:
docs.google.com/presentation...
...The content of the talk definitely drifted from when I picked the title. Mostly I talked about realizing I didn't understand reaction depth a few months ago.
