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Comment by nyeah | Hacker News Reader

>the idea of wave-packet collapse, when a measurement is done, is by itself completely unsound.

It sounds crazy if you read about the math first. Which almost everyone does ... now. But in the lab, if you set up a detector array that reports individual discrete particles arriving one at a time, that is exactly what you see. You just see random arrival times. You don't see a smooth wavefunction that then collapses.

The problem was never to start with the math and try to understand what's happening to a "wavefunction" or how the heck it could possibly "collapse." Instead they started with the crazy experimental results and made math that seems to always fit so far.

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The crazy thing to me is that QC is often treated as a normal thing that will come soon, but all we have so far are some crazy experiments we barely understand and some other crazy ideas to maybe build a useful application for calculation with that.

So I applaud all QC researchers and wish them luck. But I start paying really attention once something actually works.

As far as I understand, this is not even like Fusion. Where we knew the basic concept can work 70 years(?) ago, but still fail to build a workable power plant today, because it is just incredibly hard. And we don't know if we ever can make it work economical. But with quantum computers we don't even know whether it can work for practical applications besides quantum research at all - at least this is my understanding.

There are some objections/worries on the grounds of 'is reality fundamentally quantum or is there some other model that is classical and means QC doesn't work'. But it's also worth distinguishing the different approaches that are being used. Other QC computers are doing actual calculations, just not ones that demonstrably beat classical computers for practical applications, and if the whole concept works then there is a threshold where quantum error correction can take the whole thing from 'doesn't scale anything but the most trivial examples' to 'relevant for cryptography' in a relatively short time period.

Microsoft's approach, however, is a bit of a maverick one even within QC: what's in contention here is whether they've even made a single qubit, something other quantum computers have demonstrated conclusively (the difficult part being doing operations on those qubits with low enough noise to be able to achieve error correction).

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