Quantum computing as a field is obvious BS

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Being a gloomy sceptic of modern science, I'm inclined to believe he is right. Warning for some colourful, but well utilised bad language, some of which the forum has helpfully auto-censored for me.

Quantum computing as a field is obvious BS
https://scottlocklin.wordpress.com/2019 ... -bullshit/

Excerpts below.

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When I say Quantum Computing is a BS field, I don’t mean everything in the field is BS, though to first order, this appears to be approximately true. I don’t have a mathematical proof that Quantum Computing isn’t at least theoretically possible. I also do not have a mathematical proof that we can or can’t make the artificial bacteria of K. Eric Drexler’s nanotech fantasies. Yet, I know both fields are BS. Both fields involve forming new kinds of matter that we haven’t the slightest idea how to construct. Neither field has a sane ‘first step’ to make their large claims true.

Drexler and the “nanotechnologists” who followed him, they assume because we know about the Schroedinger equation we can make artificial forms of life out of arbitrary forms of matter. This is nonsense; nobody understands enough about matter in detail or life in particular to do this. There are also reasonable thermodynamic, chemical and physical arguments against this sort of thing. I have opined on this at length, and at this point, I am so obviously correct on the nanotech front, there is nobody left to argue with me. A generation of people who probably would have made first rate chemists or materials scientists wasted their early, creative careers following this over hyped and completely worthless woo. Billions of dollars squandered down a rat hole of rubbish and wishful thinking. Legal wankers wrote legal reviews of regulatory regimes to protect us from this nonexistent technology. We even had congressional hearings on this nonsense topic back in 2003 and again in 2005 (and probably some other times I forgot about). Russians built a nanotech park to cash in on the nanopocalyptic trillion dollar nanotech economy which was supposed to happen by now.

Similarly, “quantum computing” enthusiasts expect you to overlook the fact that they haven’t a clue as to how to build and manipulate quantum coherent forms of matter necessary to achieve quantum computation. A quantum computer capable of truly factoring the number 21 is missing in action. In fact, the factoring of the number 15 into 3 and 5 is a bit of a parlour trick, as they design the experiment while knowing the answer, thus leaving out the gates required if we didn’t know how to factor 15. The actual number of gates needed to factor a n-bit number is 72 * n^3; so for 15, it’s 4 bits, 4608 gates; not happening any time soon.

It’s been almost 25 years since Peter Shor had his big idea, and we are no closer to factoring large numbers than we were … 15 years ago when we were also able to kinda sorta vaguely factor the number 15 using NMR ‘quantum computers.’

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All you need do is look at history: people had working (digital) computers before Von Neumann and other theorists ever noticed them. We literally have thousands of “engineers” and “scientists” writing software and doing “research” on a machine that nobody knows how to build. People dedicate their careers to a subject which doesn’t exist in the corporeal world. There isn’t a word for this type of intellectual flatulence other than the overloaded term “fraud,” but there should be.

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Physicists worthy of the name are freebooters; Vikings of the Mind, intellectual adventurers who torture nature into giving up its secrets and risk their reputation in the real world. Modern physicists are … careerist ding dongs who grub out a meagre living sucking on the government teat, working their social networks, giving their friends reach arounds and doing PR to make themselves look like they’re working on something important. It is terrible and sad what happened to the king of sciences. While there are honest and productive physicists, the mainstream of it is lost, possibly forever to a caste of grifters and apple polishing dingbats.

But when a subject which claims to be a technology, which lacks even the rudiments of experiment which may one day make it into a technology, you can know with absolute certainty that this ‘technology’ is total nonsense. Quantum computing is less physical than the engineering of interstellar spacecraft; we at least have plausible physical mechanisms to achieve interstellar space flight.

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From the point of view of a theoretical physicist familiar with the topic: that person has no idea what he's talking about. Specialists don't argue with him only because they have better things to do than explaining an angry guy the countless points where he's fundamentally wrong (starting from how science works in general), to see only more and more angry denial instead of any understanding.
Really. I've been there. Including being phoned by guys like him.

Familiar enough to rebut in detail? This part stands out to me:

the number of states we’re talking about here for a 4000 qubit computer is ~ 2⁴⁰⁰⁰ states! That’s 10¹²⁰⁰ or so continuous variables we have to manipulate to at least one part in ten thousand. The number of protons in the universe is about 10⁸⁰. This is why a quantum computer is so powerful; you’re theoretically encoding an exponential number of states into the thing. Can anyone actually do this using a physical object?

as a reasonable point. It does seem an impossible engineering task when it leaves the paper. From what I've heard a "proper" quantum computer that could break current encryption methods would *only* need a cool million qubits.

A rebuttal would give the author more attention than he deserves.  Let him prove his assertions, instead of demanding that others prove him wrong.

Familliar enough to adress this

Actually, even a classical computer could be described that way:
4000 bits is 2^4000 states as well. A modern hard drive from a shelf can have e.g. 1 terabyte - that means 8 000 000 000 000 bits and 2^8000000000000 possible states. That's exactly why you build computers with exponential systems - you can encode more states than the Universe has protons. Much more. Even with a classical computer you have under your desk. Even with the processor of your phone, actually. That's the power of positional notation.

So, a quantum computer with 4000 qbits is, in that respect, similar - you have 4000 physical parts that encode 2^4000 possible states. Just like in a 0.5 kilobyte of classical computer cache - not a big deal

The only difference is that qbits are not separable. In a classical computer, you can look at every bit separately, as an independent entity. In a quantum computer, they can get entangled with each other. But the basics are the same as in a classical computer: you get 2^(a lot) because you use positional notation on (a lot) of bits.

I think you've misconstrued the point he was making. He is just advertising the scale of the problem, not making a statement of the sort you I think you've inferred.



Not an expert and at the risk of making a fool of myself: are you not here confusing data storage and computation? As I understand it, the cache is just fast, proximate, data storage, rather than computation circuitry.

FWIIW in early days of this idea, it was noticed that the growth in the number of components needed was exponential in the number of qubits. Well, this shouldn’t be a surprise: the growth in the number of states in a quantum computer is also exponential in the number of qubits. That’s both the ‘interesting thing’ and ‘the problem.’ The ‘interesting thing’ because an exponential number of states, if possible to trivially manipulate, allows for a large speedup in calculations. ‘The problem’ because manipulating an exponential number of states is not something anyone really knows how to do.

Also your "parts" here have to measure precise values, rather than just "on" and "off". Another complication.

In order to build a quantum computer, you need to control each qubit, which is a continuous value, not a binary value, in its initial state and subsequent states precisely enough to run the calculation backwards. When people do their calculations ‘proving’ the efficiency of quantum computers, this is treated as an engineering detail.

Considering the hate towards logic & reason so frequently on display here, I'm not surprised by this kind of op-ed drivel. If you want to refute a processor architecture, we're talking about the processor.

Qubits are also an outdated unit of hardware here. New products are on the market.

Get back to me when you realize you meant to say data science is BS.

Both data storage and computation use positional notation that gives n bits 2^n possibilities.

I don't know where the "growth in the number of components needed was exponential in the number of qubits" comes from. Clearly, it wasn't the case when we analysed models of quantum computers at uni. Qbits were just like bits - a component (usually imagined as a photon in optical fibre but technical details may differ for practical reasons) for each one. The beauty of it is that with quantum entanglement, you can connect each of them with every other one with just one physical element interacting with all of them - and they stay connected since then, in separate wires, going separate paths, but all the time dependent on each other's state, for as long as you can isolate them from environment noise.

It is true that quantum computers operate on - in a way - continuous states, which makes error correction waaaay more tricky than in classical digital computers. This is one of the reasons why they are unlikely to ever completely replace classical computers, probably being left to specialized computations only.

I'll see if I can find a less ranting source.

Last edited by magz on 17 Mar 2021, 3:56 am, edited 1 time in total.: Personal attack removed

Ahem, gentlemen, no personal attacks, please?

Or should I use the big exclamation mark thingy?

This is the famous Shor's algorithm:

No exponential growth of elements, the size is linearly proportional to the number of qbits.

Found a related article, which goes into more detail with less ranting.

https://spectrum.ieee.org/computing/har ... -computing

While a conventional computer with N bits at any given moment must be in one of its 2^N possible states, the state of a quantum computer with N qubits is described by the values of the 2^N quantum amplitudes, which are continuous parameters (ones that can take on any value, not just a 0 or a 1).

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Experts estimate that the number of qubits needed for a useful quantum computer, one that could compete with your laptop in solving certain kinds of interesting problems, is between 1,000 and 100,000. So the number of continuous parameters describing the state of such a useful quantum computer at any given moment must be at least 2^1,000, which is to say about 10³⁰⁰. That’s a very big number indeed. How big? It is much, much greater than the number of subatomic particles in the observable universe.

To repeat: A useful quantum computer needs to process a set of continuous parameters that is larger than the number of subatomic particles in the observable universe.

At this point in a description of a possible future technology, a hardheaded engineer loses interest.

Mikah is telling a hacker of over 20 years what for about experimental computing.

If you're not talking about quantum annealing, you're behind the times.

I'm pretty sure there are ample properties of quantum mechanics OP is ignoring here. There isn't just one quantum architecture. There are many companies & governments making various types of devices.