On Eastin-Knill Being Wrong

Wed, 01 Apr 2026 11:10:10 -0700

There are many ways to perform fault tolerant quantum gates: lattice surgery, state injection and gate teleportation, braiding, gauge fixing, code deformation… the list goes on. But, by a large margin, people’s favorite way to do a fault tolerant gate is transversally. A transversal logical gate G is performed...

[Paper] Securing Elliptic Curve Cryptocurrencies against Quantum Vulnerabilities: Resource Estimates and Mitigations

Tue, 31 Mar 2026 05:10:10 -0700

Quantum Error Correction goes FOOM

Wed, 24 Dec 2025 10:10:10 -0800

In this post: why I expect the maximum achievable qubit quality to increase drastically in the next few years.

In 2014, the John Martinis group at UCSB performed an experiment where they stored a classical bit using their quantum computer. They protected the bit with a 9 qubit

CCX+HMR isn't universal, unless you can prepare |+>

Mon, 22 Sep 2025 11:10:10 -0700

Recently, I’ve been working on a fast simulator for reversible classical circuits assisted by measurement based uncomputation. Basically it’s just doing the strategy I pointed out back in 2019. The simulator supports the CCX gate for classical computation, the HMR (Hadamard+Measure+Reset) gate for measurement based computation, and phase...

Actually, you can't test if quantum uses complex numbers

Sun, 14 Sep 2025 11:10:10 -0700

In 2021, Renou et al published the paper “Quantum theory based on real numbers can be experimentally falsified” in Nature. It caused a decent sized splash at the time. A quick search revealed articles in Quanta and Scientific American and APS News, as well as

Why haven't quantum computers factored 21 yet?

Sat, 30 Aug 2025 11:10:10 -0700

In 2001, quantum computers factored the number 15. It’s now 2025, and quantum computers haven’t yet factored the number 21. It’s sometimes claimed this is proof there’s been no progress in quantum computers. But there’s actually a much more surprising reason 21 hasn’t been factored yet, which jumps out...

[Talk at QEC2025] Yoked surface codes (and crosshair surface codes)

Mon, 18 Aug 2025 09:10:10 -0700

[Paper] A Classical-Quantum Adder with Constant Workspace and Linear Gates

Wed, 30 Jul 2025 05:10:10 -0700

[Paper] How to factor 2048 bit RSA integers with less than a million noisy qubits

Wed, 21 May 2025 05:10:10 -0700

[Talk at Simons Quantum Colloqium] Magic state cultivation

Tue, 08 Apr 2025 09:10:10 -0700

Algorithmic Assertions - Craig Gidney's Computer Science Blog