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Comment by Kequc | Hacker News Reader

Forgive me if I've missed it but I haven't seen any evidence that quantum computing has been used to solve even a very simple calculation. It seems that the purpose behind trying to build a quantum computer; is you really need to be out in front, not necessarily that it is possible.

Are quantum computers just the fusion reactors of the computing world? Maybe one won't be built for 20 or 30 years, maybe longer.

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> Are quantum computers just the fusion reactors of the computing world?

This is not the proper take-away message from the history of fusion. The expert consensus in 1976 predicted that useful fusion would not be achieved if it followed the funding trajectory it actually did end up taking.

https://news.ycombinator.com/item?id=8307584#8311566

> Forgive me if I've missed it but I haven't seen any evidence that quantum computing has been used to solve even a very simple calculation.

Factoring small numbers is a "very simple calculation," and it has been done multiple times with quantum computers: https://phys.org/news/2014-11-largest-factored-quantum-devic...

Google has been doing some interesting stuff already, like representing models of the hydrogen H2 molecule:

> While the energies of molecular hydrogen can be computed classically (albeit inefficiently), as one scales up quantum hardware it becomes possible to simulate even larger chemical systems, including classically intractable ones. For instance, with only about a hundred reliable quantum bits one could model the process by which bacteria produce fertilizer at room temperature. Elucidating this mechanism is a famous open problem in chemistry because the way humans produce fertilizer is extremely inefficient and consumes 1-2% of the world's energy annually. Such calculations could also assist with breakthroughs in fundamental science, for instance, in the understanding of high temperature superconductivity.

https://research.googleblog.com/2016/07/towards-exact-quantu...

"The largest known number factored by Shor's algorithm on a quantum computer is 21."

At this point yes . We need ~70 years of research to get to something useful ( I asked my professor about this who I studied quantum computing this).

This is not a typical view among experts. Most numbers quoted are between 10 and 30 years for commercially useful devices.

Those quotes have been around for the last 10 to 30 years, however. So 70 is a very sane number.

I work in the field and I will have to disagree - 20 years ago nobody serious would have claimed we can build a quantum computer in 10 years. There are very clear levels we need to reach to have something useful (in terms of lifetime of the qubits and number of connected qubits) and there has been extremely clear upward slope on both of those measures over the last 15 years. Extrapolating optimistically from them in 5 years we will have quantum chemistry simulators. Extrapolating pessimistically, it will take 20 or so years.

Not quite true. I can think of two well funded people in 1995-2000 who either believed (or implied to funders) that scalable quantum computing was plausible within 10 years. But those people were outliers. You're correct that it was an uncommon view, and mainstream consensus in the field was that it was many decades away. The situation today is certainly very different, and people seem much more optimistic.

This is simply not true.

I'm not talking about the pop science articles you read who find the most outlandish quote they can find. (There are plenty of those now that say 1-3 years.) I'm talking about what the actual typical practitioner says.

Relevant xkcd:

https://xkcd.com/678/

I honestly cannot remember the last time a new technology hasn't significantly overshot ETAs

That's because with new developments that do get achieved in predicted timelines, the predictions don't get mention because it's only unsurprising ordinary news. Whereas with tantalizing but out of reach technologies, we get repeated "are we there yet" articles, and skepticism makes for more popular journalism. It's a combination of selection bias and the availability heuristic.

Really? How about mapping the human genome?

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