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Comment by smsm42 | Hacker News Reader

The third stage is the hardest. Thermonuclear energy production has been sitting in "theoretically possible, but economically unviable" for decades, tons of technologies like supersonic commercial flight has been achieved and then scrapped because of practical concerns, many other technologies struggle with passing economic viability barrier. Taking that into account, getting from 2nd to 3rd stage would be the hardest task. Comparing to classic computers, their practical usability has been clear since Babbage time, so far it's not the case for QC.

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> Comparing to classic computers, their practical usability has been clear since Babbage time

Is this true? I thought that in the 40s-50s there was some argument over whether practical computers could really be built given that vacuum tubes were so unreliable. Von Neumann wrote gave a series of lectures in 1952 (eventually transcribed into an article) showing how it could be done: http://arep.med.harvard.edu/gmc/Von_Neumann_1956ro.pdf , and the argument became more or less moot once transistors arrived).

There's perhaps an analogy here to be made with quantum error correction, but that seems to be a lot harder...

Depends on what you mean by "computer", but being able to reliably calculate even just simple arithmetic has clear benefits. In the 1800s there would be countless clerks doing some sort of bookkeeping who'd benefit from it.

I suppose double entry would be your error correction. That also benefits from having a calculating machine.

The first transistors are 1947. We don't use that sort of transistor today, but unlike the vacuum tube it would have been obvious that a computer built from these transistors was viable. You can't get to the iPhone from there, but room size machines that do arbitrary Turing computation are only expensive. So that means it's in the realm of supersonic flight. If you must do it you can, but maybe you'll decide it's too expensive.

By 1950 then, the only question is whether we should, not whether we can.

Check out this one: https://en.wikipedia.org/wiki/Tabulating_machine Yes, not exactly a computer, definitely not a von Neumann one, but close enough to see how such thing would be useful. Also according to Wikipedia, this is the first thing to ever be called "super computing" device. That's what I mean - there's a long history of continuosly improving practical devices that led to the modern computer. For QC, we don't have that history.

Supersonic commercial flight is one of the most interesting. I think two strange things happened. First we got the internet - and mobile phones and video conferences and this has eroded the value of rapid physical presence. Second, and I think this is more important, people have become more willing to sacrifice their time for their career/money/firm/dream vs. family/happiness/now.

An acquaintance flew Concorde a lot in the 80's, the reason - "I could get to Heathrow in the morning, fly to New York, do a meeting, fly back and get home the next morning". Another friend is a exec at a bank now and goes on month long odysseys to the USA, Asia and Australia. The contrast in perspective and commitment is striking, I don't think that Concorde would matter at all to these folks.

Could the improvements in Business and First Class travel, combined with the increased use of private jets (also NetJets) have contributed to the downfall of the Concorde?

The more comfortable you are in the flight, the less the actual number of hours flown bothers you.

Yes - especially in flight calling, in flight working (ppt!) and in flight internet. Flight time != downtime for these folks anymore - which means that the per hour saved calculations are not going to convince finance.

Also the fact that airports are still a big time sink even with all the priority passes in the world.

No amount of money makes getting from your front door to the airport not be a massive pain potentially taking over an hour if you have some bad luck

Passenger queues are not an issue when you are departing from a GAT in your private jet. ;)

Traffic to the airport is.

Here is the issue explained in 10-minute youtube format by Wendover Productions: https://www.youtube.com/watch?v=n1QEj09Pe6k

If you can serve ads any faster with it, you bet it's gonna get deployed to production faster than Nuclear Fusion ever had hope to be :-P

quantum computing dual-state ads doing A/B testing simultaneously... I don't know if any of that just made sense, but I bet you could get some VC funding if you pitched it!

I don't think it's true for quantum computers. Folding proteins and stuff is good use-case of the cause but the real drive is the military. Same as for gen-AI. If you don't r&d this but Chine does - you're fucked. So the only way to do not become in the disadvantageous position - is to reason it yourself.

If the military is paying for it then it's already in stage 3. Just because something isn't readily available to the public doesn't mean it's a failure - I can't buy a rocket but the various space programs still do lots of cool things and they have money to pay for it.

Military pays for a lot of stuff that then is not going anywhere. Just as other venture funds do. You can't win without taking some risks. But that doesn't mean everything the army pays for automatically is a great thing.

The military what? Comparing again to computing engines, even when computers were not at all like they are now, there were always lots of people queueing around them with workloads they want them to do now - and which computers could help them with as they are, not 200 years in the future. For QC, I do not see many users with workloads that can be served right now. I don't say it shouldn't be developed because of that - lots of things took time to bring to maturity - but we should be ready for it taking a long time to get to real usefullness.

> the real drive is the military

Although military investment has driven many different technologies over the years, ‘the military’ is actually a complex mix of the Armed forces themselves, government acquisition organisations, and prime contractors and their supply chains. The resultant acquisition processes of many countries are glacially slow, with sometimes decadal timescales from requirements definition to delivery of full operational capability. Military acquisition is not agile, except when urgent operational requirements force rapid tech change by taking acquisition shortcuts.

So relatively we will all be about the same, but in absolute terms we will all be worse off?

Where have I heard this before...

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