I think the comparison is still reasonable: while we do not have scalable quantum computers, the technologies developed for them have actually seen a lot of use: squeezed light and non-classical light, color centers, Josephson junctions, nonlinear-optics at the single-photon level, to name a few "terms of art" that should be google-able, are crucial for precision sensing and telecom.
The nonlinear optics is what enables optical signal modulators. For modulation of classical optical signals it is not necessary to have a "strong nonlinearity at the single photon level". However, that is being developed for quantum computing applications and as a side effect it makes today's optical modulators much better.
Telecom signal modulators are almost exclusively based on the Kerr effect or acousto-optics. Both effects have been known for at least 100 years and have nothing to do with nonlinear optics. The development of modern modulators was always driven by telecom and then applied to scientific experiments, not the other way round.
There might be some semantic misunderstanding here. "Kerr effect" is "nonlinear optics" in my book - it works both at the low GHz frequency of electro-optics and at the high THz frequencies of pure optics. I agree with the rest of your statement (and it does not seem to be in conflict with the initial comparison: vacuum tubes were being developed for 50 years due to the needs of the radio industry before they became viable for computation).
And the direction symbiotic improvements is not necessary as clear: there are academic groups solely focused on quantum optical effects, whose research then gets reused by the telecom industry and vice versa. These quantum research groups would be dead in the water if it was not for the fab capabilities initially developed by telecom folks, but they have certainly surpassed them by far now (in one-off "hero" devices).
P.S. Same with acousto-optic devices. What you would find in a quantum computing lab is far more impressive than what is being deployed today. Even if the quantum computing field is a bust, the tech they developed would improve telecom state of the art by orders of magnitude.
Right now it is a pre-transistor in the 1920s and 1930s.
Vacuum tubes are analogous to the computers that we have now. In 1925 a patent for the concept of a FET was filed. It wasn't until 1948 that we had a working transistor.
That took 23 years to go from concept to useful invention. It isn't too surprising that a quantum computer is harder.
As far as I know - and we still had some tube radios at home when I grew up - they were used pretty much right away. For radios, and replacing mechanical relay switches, over which there obvious advantage was that since the tubes were not mechanical they would last longer, especially important in systems with lots of them.
So I'm not completely sure and somebody with definite knowledge should chime in, but I think they were not some "we have no idea what to do with this" but where useful from early on, as soon as the manufacturing method was solid. They were used for "normal" electronics well before they were used for the early computers. Even though Google search - which I just tried - also seems to have a bias and mostly associate those vacuum tubes with computers and forget all about the many other uses. It was the predecessor of diodes and transistors in addition to being better than mechanical relays.
(just one of the earliest commercial use cases as example for how short the period was between invention and wide-spread use)
> Dr. Lee deForest invented the vacuum tube in 1906. His tube, which he called the "audion," was first developed as a detector of radio waves and was quickly adopted by shipboard operators. Later experimentation, by deForest and others, showed the ability of the vacuum tube to generate radio signals with far greater precision than earlier systems. By 1914 the essentials of tube-based transmitters had been worked out.
Radio existed (as you say) before the tube, but it took time to get the tube into real-world use. I guess this is somewhat like computing ; computing has existed in many forms, mechanical through to IC designs we have now.
But quantum? It's in a lab, and real-world applications are being worked out.
Paralleling back to radio again, people knew tubes would be useful, but it took 20+ years to make them mass producible, and make tubes usable, and redesign radios to use them. This, to me, sounds like quantum computing.
We can think of things I suppose to use them for (perhaps I was hasty on this point in my prior post), but we aren't there yet. And really, looking at the tube -- did anyone think they'd be used to make massive computers even?
I bet quantum computing will be the same way -- uses we're not aware of now.
You need to get your information from places other than Wikipedia. The vacuum tube was invented in 1904 and entered mass production by RCA in 1920 after several rounds of improvements. D-Wave started demonstrating its QC product in 2009 and here we are 13 years later with basically nothing. Are you going to tell us that QC will be commercially viable in three years?
It's honestly just a really bad analogy. Evacuated tubes were not pursued en-masse as an end unto themselves the way quantum computing is being pursued. Their development was as a side fascination for a handful of researchers or they were advanced because they were directly applicable to some goal of a researcher with maybe some mild tweaking. They were not a moonshot and they developed along similar lines as most useful "inventions" of today.
Quantum computing isn't even really comparable to ENIAC. Because the fundamental parts of ENIAC were known to be capable of doing what was required before the machine was built. There were analogus precursors to basically all the parts of the machine. The engineering challenges came with integration and at scale but fundamentally there wasn't a question of whether it could be done or not. We can't say the same yet of quantum computing.
IMO, quantum computing is more like space travel ca. the 1950s. We've got a lot of information: rockets look promising, we've learned a lot about the environment pilots will need to operate in up there, etc but no one really knows how far this can go and certainly we can't say if it will ever be profitable.
> It's honestly just a really bad analogy. Evacuated tubes were not pursued en-masse as an end unto themselves the way quantum computing is being pursued
No, it's not. The Vacuum tube was sold for commercial and industrial use starting from 1915 for rectification. And most of the research spending went into it after it shown some promise from commercial application.
Not arguing though if pursuing something just for research is bad, just saying vacuum tube research was nothing like quantum computer research.
> just saying vacuum tube research was nothing like quantum computer research.
That's what I'm saying. Vacuum tubes had various evacuated tubes as their precursors which had uses in experimentation and industrial applications. This led to a step by step development process with continuous subsequent innovations building on each other. Quantum computing on the other hand is kind of an all or nothing proposition with many problems that must be solved which only produce value when functioning as part of the whole.
I don't think the development of classical computing is a good analogy either as the shared memory computer had various electromechanical precursors that had utility all of their own.
> Quantum computing with todays technology :: Classical computing in the early era of vacuum tubes
There's still a big difference.
Even in the earliest era of computing with vacuum tubes (and even before), they were building machines that produced useful results: artillery tables, H-bomb simulations, cryptanalysis, etc.
Most things these machines were used for were simply impractical without them.
There's nothing even remotely analogous with quantum computing.
Well, to be fair: quantum computers can do practical computations—but because “normal” computers are so unbelievably well developed, it is not practical to do them with quantum computers.
The earliest era of computing was mechanical. The mechanism of thermionic transmission (vacuum tubes) was invented by Edison in 1883. The Colossus computer, with thousands of vacuum tubes, was the first practical use of vacuum tubes for computation, in 1943. We cannot yet assemble thousands of qubits together. Once we can do that, we will be able to perform many useful functions. However, even with thousands of qubits, many of the functions will be more practical to run on a classical computer (because classical computers are amazing and continue to develop).
> The Colossus computer, with thousands of vacuum tubes, was the first practical use for computation, in 1943.
I don't think this is true. Perhaps the Colossus is what we would call the "first computer" by some definition but electro mechanical computing devices built for specific purposes preceded it. There wasn't a 60 year gap of investment with no practical application of classical computing.
Classical computing was built up over time with practical utilith along the wya. The vacuum tube eventually became a useful component of it.
No, current quantum computers cannot do any practical computations. The gate errors are astronomical compared to even the earliest digital computers. Any algorithm with more than a few gates will produce just noise.
How is it even remotely close?
Vacuum tubes were a thriving industry, producing many groundbreaking products and services.