The field of quantum computing has made a bizarre turn over the past years. There exists a myth that qc is on its way to widespread use.

This paper is a prime example. It starts with the sentence: "Quantum information processing is steadily progressing from a purely academic discipline towards applications throughout science and industry."

Except, no it does not. Quantum computing has no practical uses today. It's years, maybe decades away from widespread practical applications.

This is an interesting research field, but the field is just in the stages of having shown that you can do anything at all with a QC that you couldn't do with a normal computer.

But this computer does have a very practical use. It is a research object. It will attract grad students and grant money. The product is the ability to say that you have a "quantum" computer in your lab. It completes that task the moment the box arrives. Plugging it in and actually computing something is just a bonus feature.

So basically Nuclear Fusion? Or I am under the impression even Nuclear Fusion is far closer to commercial application than QC?

Nuclear fusion is a reality, it already works in bombs and the stars, and there are real reactors outputting significant energy. Will we ever see a reactor that doesn't tear itself apart in a few hours and doesn't cost at least a thousand times as much as solar panels? Who knows. But the physics foundation is sound, the missing part is "just" engineering.

Quantum computing relies on the universe being based on non-classical computation principles. We still don't know if the universe has such properties or if the quantum mechanics we observe are simply the result of a more complicated classical model, which would inherently limit the theoretical capabilities of quantum computers.

But the theoretical part aside, quantum computing is just not really evolving. When I first heard about 50+ qbit quantum computers I though it was a sign of clear progress, but I think it is just mostly moving the goal post, the requirement that you have to do some sort of computation to call the device a computer just kind of slipped away. Better freezers have of course done their part, but that just isn't going to push us anywhere near useful.

When you first heard about 50+ QCs, like, a couple years ago? That timespan is more or less like yesterday in cutting edge research, especially in such capital intensive research like QC. QC in unambiguously progressing, but it still hasn’t achieved its grander goals.

Give it a few more years then.

How many? 30? [0]

[0] https://www.discovermagazine.com/technology/why-nuclear-fusi...

Miniaturizing quantum computers is the absolute last priority issue in the field right now.

Making quantum computers “scalable” means overcoming challenges in qubit coherence times and operational fidelities, as well as manufacturing yield.

Putting a quantum computer—that doesn’t do anything remotely useful—on a rack, or in a glass case, or whatever is, in my not so humble opinion, just a gimmick.

While I think the miniaturization is a gimmick, it’s nonetheless nice to see another quantum computer built with respectable fidelities. It’s not good enough to do anything other than further science experiments, but it does show the scientists’ care for the details and the design.

This seems a bit reductive.

Sure. There are larger challenges but size, specialization and cost are three things that prevent adoption of this technology at all universities and some companies.

Having more adoption even if its "useless" right now means more people looking for useful things to do.

I think this is a key misunderstanding.

The issue is not that we don't know what useful things to do with a QC. The issue is the quantum computers that exist today are not able to do those things.

"Adopting" a machine that can't do anything you couldn't do on your laptop won't help. The challenge for QC to become useful is to scale up and provide working error correction.

Genuinely curious then. When you say that it can't do anything that my laptop can't do. Is that based on simulation of actual quantum methods with all of the quirks or simply traditional algorithms?

If it's not truly simulation, there seems to me a ton of value in having even a little bit of access to something like this.

The wavefunction of an n qubit system is representable by a 2^n vector of complex numbers [1]. Using single precision floats [2], a 10 qubit wavefunction is 8 KB, 20 qubit = 8 MB, 30 qubit = 8 GB and 40 qubit = 8 TB.

Hence a run-of-the-mill laptop can easily simulate a perfect 30 qubit computer, provided you are using a sufficiently performant simulator (such as https://github.com/qulacs/qulacs ).

[1] This is actually a pessimistic upper bound for the classical simulation because current quantum hardware is not fully connected and not fully coherent.

Most problems of interest (optimization, chemistry etc) also do not ever generate fully entangled wavefunctions and so can be simulated with significantly less resources.

So for any applications (beyond simulating quantum advantage experiments built specifically to make classical simulation hard), classical computers are crushing quantum computers.

[2] Because QM is a linear theory, numerical precision isnt an issue, as it would be in a chaotic classical simulation of eg fluid dynamics.

It's both. You can easily simulate 11 qbits.

There's a commercial product for classical simulation of small QPUs [0]. With dedicated hardware handles up to 41 qubits. I'm not affiliated with the company or endorsing their products, just pointing out that they exist.

[0] https://atos.net/en/solutions/quantum-learning-machine

You can also do this with purely free and open source software like [0].

[0] https://github.com/quil-lang/qvm

I agree completely, I would love quantum computers to be in a place where all universities and most companies can do useful stuff with them, but they aren't and these companies which pretend that they are seem like scams.

The rabbit hole goes deep in this. Form factor isn’t limiting adoption. Bad performance and the fact you need a team of physicists to calibrate the machine daily are two simple examples limiting adoption more than size. I’m not saying miniaturization isn’t useful, I’m saying it’s last on the list to care about.

> I think the miniaturization is a gimmick

I suppose you can make it useful by inserting more q-bits into the expansion slots (?)

That's not how it works.

Two 11 qbit quantum computers are not like one 22 bit quantum computer.

Quantum computers become powerful when you can entangle many qbits. That's also the challenge, because building such a thing is hard.

“We can’t make it work as a computer, so we made it look like a computer”

Pretty amazing it was made so small, however the specs, which are impressive, state of the art, are still far from what would be considered a scallable quantum computer: 11 qubits with gate fidelities of 99.9%

It's even worse I think. The quantum course represents a scam, as these 11 qubits are "faked" based on magnetic principles. Think of it like Bulldozer's 8 "cores".

There are shared components?

"Where should we put it?" "Just anywhere over there" "What about in this server rack?" "Sure, that's a super position"

How did they get past the supercool problem???

Doppler cooling inside the computer and fans inside the rack. It’s all wrote in the pdf, read it.

Ions or neutral atoms don’t need the same kind of cooling as superconducting qubits need, which might be what you’re thinking.

Can it run a toaster yet?

Quantum computing will enable sustainable cold nuclear fusion which in turn will enable quantum computing.