But perhaps my opinion is due for an update? I know some real quantum computing people read this blog, so I welcome comments.
Here's part of what I wrote back:
I'm not sure what is meant by "tipping point" -- I don't think we know yet what qubit technology can be scaled to the point of making Shor's Algorithm feasible. The threat to classical cryptography is still very far off -- you need millions* of qubits and the adversary can always just increase the key length; the tradeoffs are likely to be in favor of the classical method for a long time.These are the Preskill slides I mentioned -- highly recommended. John Preskill is the Feynman Professor of Theoretical Physics at Caltech :-)
Noisy quantum simulators of the type Preskill talks about might be almost possible (first envisioned by Feynman in the Caltech class he gave in the 1980s: Limits to Computation). These are scientifically very interesting but I am not sure that there will be practical applications for some time.
* This is from distant memory so might not be quite right. The number of ideal qubits needed would be a lot less, but with imperfect qubits/gates and quantum error-correction, etc., I seem to remember a result like this. Perhaps millions is the number of gates, not qubits? (See here.)
Here's a summary of current and near-term hardware capability: