I Will quantum computation lower energy requirements?

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According to this article, written by D-Wave's CEO, the advent of quantum computers will "change the way the world uses energy". However, on a first reading, it sounds like an advertorial that pushes nonsense. I'm no energy scientist (unless you put high energy physics in that category for some reason), so if anyone has something to say about this, I'd be very interested.

One claim the author makes is this:

Thanks to the “weirdness” of quantum mechanical properties, qubits can represent both 1s and 0s at the same time, allowing quantum computers to find optimal solutions that classical systems cannot, all while using less energy.

Here’s why: For a quantum processor to exhibit quantum mechanical effects, you have to isolate it from its surroundings. This is done by shielding it from outside noise and operating it at extremely low temperatures. Most quantum processors use cryogenic refrigerators to operate, and can reach about 15 millikelvin–that’s colder than interstellar space. At this low temperature, the processor is superconducting, which means that it can conduct electricity with virtually no resistance. As a result, this processor uses almost no power and generates almost no heat, so the power draw of a quantum computer—or the amount of energy it consumes—is just a fraction of a classical computer’s.

This doesn't sound at all convincing to me. Convential computer chips can also be run at low temperatures, but refrigerating stuff costs energy too, and it's hard + expensive, so that's why you don't run your laptop at a few milliKelvins. Furthermore, lots of things that computers do will not at all be taken over by quantum chips, since there is only a small set of problems that can be solved more efficiently by quantum computation than by classical computation (and I suppose even that is still up for debate).

I see the value of hybrid computation, and what advantages quantum computers can provide us with, but I think it's stretching it too far to say that it will cause an energy revolution. Therefore I don't really understand the author's angle, it seems there are so many good things to be said about quantum computers that this article just seems to completely miss the point - and that's coming from a CEO of a quantum computing company. (I'm not going into whether D-Wave constructs actual quantum computers at all, since at this stage I suppose nobody can say for sure whether that's the case)

I'd be very happy to hear a more informed opinion on this, especially if I'm completely wrong. Thank you very much in advance!
I think your view is spot on.

I'm no expert, but I would imagine that the energy budget of "computing" world-wide is dominated by the consumption of the millions (billions?) of monitors, not the CPUs.

I'd be very happy to hear a more informed opinion on this, especially if I'm completely wrong.
Me, too.


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I'm no expert, but I would imagine that the energy budget of "computing" world-wide is dominated by the consumption of the millions (billions?) of monitors, not the CPUs.

Me, too.
Good original question. Many facets to the answer,
The display of a smart phone is certailny a major factor in battery drain. (Say a few Watt Hours per owner per day) Similar computing circuit power is used for a big screen display.
Communication Centres (internet) take incredible amounts of Electrical Power and have to dissipate MW with their cooling circuits . Each user will take their share (plus the switchers and routers on the way) If quantum computing ever moves from the high cost 'mainframe' scale to the personal level then i would guess that the display power will still need to be similar to present day so your original pproposition would be even more accurate, I think.


I do not consider myself an expert in quantum computing, but a rookie (I'm entering in the field). Therefore, if someone wants to correct/integrate this, I will be glad.

As I understand it, a quantum computer is (very roughly) like a parallel machine where the number of processor grows exponentially with the number of "physical resources" used. This descends from the fact that if your computer has N qubits, the vector space representing the state of your computer is the tensor product of the spaces representing the state of the single qubit. Since the number of dimension of the tensor product of two spaces V and W is the product of the dimensions of the two original spaces (i.e., dim(V) dim(W)), you can see that the dimension grows exponentially with the number of qubits. For example, if every qubit is a particle with a spin (up or down), the vector space associated to a qubit has dimension 2 and the vector space associated to the whole computer has dimension 2^N. You solve a problem with a quantum computer by having the state evolve (in the programmed way), "exploring" a number of potential solution that grows exponentially with the computer size.

It is true that a quantum computer must be kept cold, much colder than, for example, superconductive digital electronics: a quantum computer works at few mK, while superconductive electronics can work at the "hotter" :-) 4K (well, it is 2-3 order of magnitude hotter...). Keeping stuff so cold it is not easy and requires energy, but quantum computers compensate the consumption of the cooling system with their exponential efficiency.

My feeling, however, is that quantum computers are more suited for combinatorial-like problems (i.e., integer factorizations, NP-hard problems, ...), it is hard for me to imagine how a quantum computer could be used, for example, to solve a differential equation (although, I remember I read something about solving linear systems).

Summarizing, my feeling is that quantum computers (when the huge load of technical difficulties in having many qubits will be solved) will be a very powerful tool at least for some classes of problems. It is very difficult to envision a future where everyone will have a quantum computer working at 10mK on the desk or in the smartphone... Saying that it will be a revolution in energy management sounds like a kind of hyperbole

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