It is the paradox of PQC: from a classical security point of view PQC cannot be trusted (except for hash-based algorithms which are not very practical). So to get something we can trust we need hybrid. However, the premise for introducing PQC in the first place is that quantum computers can break classical public key crypto, so hybrid doesn't provide any benefit over pure PQC.

Yes, the sensible thing to do is hybrid. But that does assume that either PQC cannot be broken by classical computers or that quantum computers will be rare or expensive enough that they don't break your classical public key crypto.

The thing is, producing the right isotopes of uranium is mostly a linear process. It goes faster as you scale up of course, but each day a reactor produces a given amount. If you double the number of reactors you produce twice as much, etc.

There is no such equivalent for qubits or error correction. You can't say, we produce this much extra error correction per day so we will hit the target then and then.

There is also something weird in the graph in https://bas.westerbaan.name/notes/2026/04/02/factoring.html. That graph suggests that even with the best error correction in the graph, it is impossible to factor RSA-4 with less then 10^4 qubits. Which seems very odd. At the same time, Scott Aaronson wrote: "you actually can now factor 6- or 7-digit numbers with a QC". Which in the graph suggests that error rate must be very low already or quantum computers with an insane number of qubits exist.

Something doesn't add up here.

What surprises me is how non-linear this argument is. For a classical attack on, for example RSA, it is very easy to a factor an 8-bit composite. It is a bit harder to factor a 64-bit composite. For a 256-bit composite you need some tricky math, etc. And people did all of that. People didn't start out speculating that you can factor a 1024-bit composite and then one day out of the blue somebody did it.

The weird thing we have right now is that quantum computers are absolutely hopeless doing anything with RSA and as far as I know, nobody even tried EC. And that state of the art has not moved much in the last decade.

And then suddenly, in a few years there will be a quantum computer that can break all of the classical public key crypto that we have.

This kind of stuff might happen in a completely new field. But people have been working on quantum computers for quite a while now.

If this is easy enough that in a few years you can have a quantum computer that can break everything then people should be able to build something in a lab that breaks RSA 256. I'd like to see that before jumping to conclusions on how well this works.