Q-day estimates are sensitive to several factors; e.g., hardware qubit counts, error correction overhead, and algorithmic efficiency (e.g., better factoring approaches could compress the timeline meaningfully without any hardware breakthrough).

Migration complexity side is also not straightforward. Cryptographic primitives tend to be deeply embedded in ways that are not always easy to find. FWIW, we built a free scanning tool for developers to find and remediate cryptographic vulnerabilities in their repos (still in beta: https://app.threatpoint.com).

2029 might be conservative or optimistic depending on which variable moves first.

We are still in a regime where the growth of logical qubits is far below the point of any practical computing utility let alone at a level capable of breaking existing codes. While it’s correct to be proactive at the security end, if you take the current rate of improvement in logical qubits and project it forward you’ll get something beyond 2040. I built a probabilistic model of logical qubit improvement and the median ends up being further out (probably should publish this somewhere). I’d like to point out that I’m not purely negative; I was surprised to calculate we can make enough He-II to make it all go!

Of course such a model cannot predict a fundamental breakthrough nor can it predict whether there is some kind of fundamental limit to the size of such a quantum system before we have coherence collapse. This is an interesting question for quantum mechanics however.

In summary, quantum computing feels analogous to fusion, a technology that’s always 20 years away.

Oh and don’t get me started on AGI. Lol.

If it’s three years away that means state-level actor(s) has it now.

I wonder what a quantum backdoor would look like.