While I'm still eager to see where Quantum Computing leads, I've got a new threshold for "breakthrough": Until a quantum computer can factor products of primes larger than a few bits, I'll consider it a work in progress at best.
Depending on your interests, the initial insensitivity of largest-number-factored as a metric is either great (it reduces distractions) or terrible (it fails to accurately report progress). For example, if the actual improvement rate were 10x per year instead of 2x per year, it'd be 3 years until you realized RSA2048 was going to break after 2 more years instead of 12 more years.
And as I've mentioned elsewhere, the other QC problems I've seen sure seem like simulating a noisy circuit with a noisy circuit. But I know I don't know enough to say that with confidence.
I'm not trying to disparage quantum computing. I think the topic is fascinating. At one point I even considered going back to school for a physics degree so I would have the background to understand it.
There are several experiments that claim to factor 15 with a quantum computer (e.g. [1][2]). But beware these experiments cheat to various degrees (e.g. instead of performing period finding against multiplication mod 15 they do some simpler process known to have the same period). Even without cheating, 15 is a huge outlier in the simplicity of the modular arithmetic. For example, I think 15 is the only odd semiprime where you can implement modular multiplication by a constant using nothing but bit flips and bit swaps. Being so close to a power of 2 also doesn't hurt.
Beware there's a constant annoying trickle of claims of factoring numbers larger than 15 with quantum computers, but using completely irrelevant methods where there's no reason to expect the costs to scale subexponentially. For example, Zapata (the quantum startup that recently went bankrupt) had one of those [3].
[1]: https://www.nature.com/articles/414883a
Agreed. Although I'm no expert in this domain, I've been watching it a long time as a hopeful fan. Recently I've been increasing my (currently small) estimated probability that quantum computing may not ever (or at least not in my lifetime), become a commercially viable replacement for SOTA classical computing to solve valuable real-world problems.
I wish I knew enough to have a detailed argument but I don't. It's more of a concern triggered by reading media reports that seem to just assume "sure it's hard, but there's no doubt we'll get there eventually."
While I agree quantum algorithms can solve valuable real-world problems in theory, it's pretty clear there are still a lot of unknown unknowns in getting all the way to "commercially viable replacement solving valuable real-world problems." It seems at least possible we may still discover some fundamental limit(s) preventing us from engineering a solution that's reliable enough and cost-effective enough to reach commercial viability at scale. I'd actually be interested in hearing counter-arguments that we now know enough to be reasonably confident it's mostly just "really hard engineering" left to solve.
:-)
In general to the ‘Is crypto still safe’ question, the answer is typically no - not because we have a quantum computer waiting in the wings ready to break RSA right now, but because of a) the longevity of the data we might need to secure and b) the transition time to migrate to new crypto schemes
While the NIST post quantum crypto standards have been announced, there is still a long way to go for them to be reliably implemented across enterprises.
Shor’s algorithm isn’t really going to be a real time decryption algorithm, it’s more of a ‘harvest now, decrypt later’ approach.
This. Small, incremental and predictable advances aren't breakthroughs.
My very layman understanding is that there are certain things it will be several orders of magnitude better at, but "simple" things for a normal machine quantum will be just as bad if not massively worse.
It really should be treated as a different tool for right now. Maybe some day in the very far future if it becomes easier to make quantum computers an abstraction layer will be arrived at in some manner that means the end user thinks it's just like a normal computer, but from a "looking at series of 1/0's" or "looking at a series of superimposed particles" it's extremely different in function.
The one a few years ago where Google declared "quantum supremacy" sounded a lot like simulating a noisy circuit by implementing a noisy circuit. And that seems a lot like simulating the falling particles and their collisions in an hour glass by using a physical hour glass.
Google's supremacy claim didn't impress me; besides being a computationally uninteresting problem, it really just motivated the supercomputer people to improve their algorithms.
To really establish this field as a viable going concern probably needs somebody to do "something" with quantum that is experimentally verifiable but not computable classically, and is a useful computation.
> breaking some cryptography schemes it not exactly the most exciting thing IMHO
You're probably right that we'll migrate to QC-resistant algorithms before this happens, but if factoring was solved today, I think it would be very exciting :-)