Saturday, October 13, 2018

Analyzing a spooky anti-quantum article from Poland

Jitter informed us about a short popular article published on Thursday:
The Spooky Reality Behind the Quantum Universe –“We Haven’t a Clue What It Is” (Daily Galaxy)
Jitter has summarized the text as saying that "it's claimed that quantum mechanics is no longer required for a single particle" – a clearly incorrect claim.

Let us look how stupid the claims are. Most of the irrational statements are actually being included in a majority of similar anti-quantum and spooky quantum articles.

First, as Edwin pointed out, the title is tautologically stupid. The people are looking for something spooky that is behind the Universe. But the word "Universe" should describe everything that exists. It's the most inclusive set – to say the least, it contains everything that exists physically.

Because it contains everything that exists physically, nothing can be behind it. If there were something behind the Universe, there would be a room with stuff behind and therefore outside the set that is called the Universe. But that contradicts the definition of the Universe as "everything that exists".

Their actual goal is to say that there is "something behind quantum mechanics". There's nothing "behind it", quantum mechanics is the correct and most complete framework to describe physics. But their usage of the "quantum Universe" as an object behind which a bogeyman hides is particularly silly. It should be easy to understand that quantum mechanics is a theory and a theory may have its representation of the Universe. But within every theory, the Universe should still contain everything that exists.

They don't just want "something that cannot exist to exist". They want this impossible thing to be spooky. Richard Lindzen has once described climate alarmists as little kids who are trying to maximally scare each other by hiding in the closet. You can see that the same description applies to the anti-quantum inkspillers. They want to scare each other by spooky things that are said to be hiding at places that cannot exist according to the basic logic.

The bogeymen are said to be hiding in closets that can't exist, "we don't have a clue what these bogeymen are", but the readers are still expected to be spooked – and to click at such articles and bring some revenue to the writers, I guess. Now, the subtitle contains a sentence that reappears later in the article:
The world of quantum phenomena is full of paradoxes incomprehensible to human intuition and inexplicable to classical physics.
This sentence displays an illogical thinking or the basic misunderstanding of some words at several places – it is a sequence of words that is characteristic for a scientifically illiterate speaker but similar sentences are repeated and connected with science so often that tons of people no longer understand that these rituals belong to the category of superstitions and they have nothing to do with science.

First, the world of quantum phenomena is "full of paradoxes". Now, the word "paradox" should represent a contradiction. Needless to say, a genuine paradox ultimately cannot exist. The only thing that can exist is a situation that looks paradoxical. But when we correctly understand things and fix some incorrect assumptions of ours, the contradiction goes away. It means that the things called "paradoxes" are interesting situations in which you have to learn something if you want to see that the world makes sense.

The sentence is deliberately vague when it comes to the question whether the speaker claims that there is a real paradox, a real contradiction, or just something surprising. The words immediately following the word "paradoxes", namely "incomprehensible to human intuition", already soften the word "paradox" dramatically. They make it sound as if the speaker doesn't have any paradoxes in mind – just something that is "incomprehensible to human intuition". In this sense, it's being immediately admitted that the word "paradoxes" was a vast exaggeration – the readers are being sold snake oil.

The phrase "human intuition" is extremely problematic because intuition is a very personal thing. Some people find certain things intuitive, others don't. Others may find other things intuitive – or they don't find anything intuitive. The claim that all humans should have the same intuition that makes quantum mechanics look "paradoxical" is just a piece of propaganda. Quantum mechanics may be intuitively understood and in many respects, it's more intuitive than classical physics. For example, the "number of states" (dimension of a Hilbert space) may be considered an integer which is much more intuitive than the "volume of the phase space in some strange units" which is what replaced the "number of states" in classical physics.

At the end of the problematic first sentence, the paradoxes are also claimed to be "inexplicable to classical physics". The seemingly grammatical problem with this sequence of words is subtle but far-reaching. You know, "classical physics" is a theory or a class of theories – a framework in physics – not a schoolkid. So if we want the paradoxes to explained, "classical physics" might only be employed as an active player, as the "explainer", not as a passive element, the "explainee". "Classical physics" just doesn't listen to someone else's explanations. Instead, "classical physics" should try to explain something – and either succeed or fail.

So once you realize that "classical physics" isn't a schoolkid who listens to someone else, you must agree with me that the only meaningful preposition could have been...
...inexplicable by classical physics.
The words "to" and "by" are tiny and someone may be surprised that I dedicate several paragraphs to the difference between them. But such seemingly "tiny" defects actually play a huge role in the process of brainwashing of the laymen by the pseudosciences. Let's keep on thinking about the difference between "inexplicable to classical physics" and "inexplicable by classical physics".

What would be different if the article simply wrote that quantum phenomena are "inexplicable by classical physics"? What would be different would be that the sentence would actually make complete sense, it would become a matter of common sense, and it would cease to be spooky. Quantum phenomena are inexplicable by classical physics. What a shock! That's why we call them quantum phenomena – the adjectives "quantum" and "classical" are considered opposite to each other. Quantum phenomena are inexplicable by classical physics for the same reason why e.g. female reproductive organs cannot play the male role in an intercourse. Maybe you can find a better example. ;-)

At any rate, the statement is completely obvious. We have some new phenomena that an old theory wasn't good enough to explain, so they need a better and more complete theory to be explained. With the word "by", the sentence would become sensible and comprehensible and that's exactly what the writers of similar texts cannot allow because the persistent irrationality and confusion is how they make their living.

That's why they replaced the word "by" by (or with) the word "to", too. They changed the status of "classical physics" from a "theory" that should explain something to a dissatisfied schoolkid who wants to hear an explanation and who is not satisfied! So physical theories such as "classical physics" are presented in an anthropomorphic way. They're like schoolkids. But as I said, the truly important addition is that this schoolkid named "classical physics" is dissatisfied.

In the mental world of similar anti-quantum articles, "classical physics" becomes a political representative who defends the prejudices and emotions of the people who have trouble to understand quantum mechanics. "Classical physics" is a loud and assertive schoolkid who is sent to quantum mechanics courses with the task to scream at the instructor. "Classical physics" is a cheeky bastard who constantly yells and demands an "explanation".

Why do they want this particular anthropocentric role for "classical physics"? It's simple. Because they don't really want to learn explanations that work. Instead, these people want their (incorrect) assumptions to be defended by somebody. This particular ally, a cheeky kid who may do some work in this defense of the prejudices, is called "classical physics". So this cheeky kid keeps on interrupting and disrupting a quantum mechanics course – every quantum mechanics course. This cheeky kid screams that none of the explanations by quantum mechanics are good explanations for him or her. These explanations are morally reprehensible hate speech that doesn't belong to safe spaces. "Classical physics" screams to feel "offended" – the claims by the quantum mechanics instructor diminish her importance and prestige. Surely it's offensive to point out that physics was invented and overwhelmingly built by men, too. Einstein was also a woman, "classical physics" demands the instructor to repeat.

What I want to say is that the very usage of "to" instead of "by" actually shows that these people don't want to respect totally basic rules of science such as the rule that scientific theories are actually supposed to explain and predict the phenomena. The theories such as "classical physics" and "quantum mechanics" must play an active role, an analogously active role, and their success in reproducing the outcomes of the phenomena (which must be judged impartially) is what decides which theory wins.

So for the schoolkid named "classical physics", screaming that it wants to be "explained" something and it is dissatisfied is not enough. Science has a different idea what to do with competing theories – e.g. with classical physics. It's being looked how well these competing theories actually explain or predict the phenomena. And because "classical physics" just didn't pass the tests, even some very basic and clearcut tests, it was thrown out of the window where it had the time \(t=\sqrt{2h/g}\) for its obnoxious screaming. After it collided with the sidewalk, "classical physics" survived as an entity that may still be brought to a classroom but, confined to the wheelchair, it can no longer do the most demanding modern tasks. And it doesn't have the mood to scream and demand "explanations" anymore. It's a theory that has already lost the race – and it did so over 90 years ago.

Yes, I could write a really long book about the difference between "by" and "to" in that sentence.

The following paragraph says:
With the aid of simple theoretical models it is possible to build systems operating strictly according to the rules of classical physics, yet faithfully reproducing the predictions of quantum mechanics for single particles – even those that are the most paradoxical! So what is the real hallmark of quantum behavior?
No. Nothing in the real world operates precisely according to the rules of classical physics. Classical physics may be an extremely good approximation for many systems and phenomena but it can never be the precise theory because the only precise framework that describes any phenomena in the world around us is quantum mechanics.

Also, classical and quantum mechanics are strictly unequivalent. You can't replace the former by the latter. Also, it is not good physics to imagine that the situations are being divided to 1-particle and many-particle cases. Both quantum mechanics and classical physics may deal with lots of systems where the "number of particles" isn't even well-defined – such as fields. Classical fields don't contain any countable "particles" at all. Quantum fields do contain the number operator \(N\) but it only behaves properly in the Fock space of a free theory.

Generic states that you produce in an interacting quantum field theory have an ill-defined \(N\), too. In particular, the number of particles \(N\) diverges in Quantum Electrodynamics whenever any charged particle moves with a nonzero acceleration. An accelerating charge produces electromagnetic radiation – including very soft (low-frequency) radiation that carries a finite total energy but a logarithmically divergent number of photons! This divergent number of soft photons is the reason why we must deal with infrared divergences in loop diagrams, and so on.

So 1-particle and \(N\)-particle systems in quantum mechanics are just some of the simplified yet important examples of quantum mechanical theories that may be taught – and the fixed value of \(N\) means that we only study the non-relativistic approximation of the quantum mechanical theory because relativistic quantum mechanical theories unavoidably allow \(N\) to be changed, and with accelerated charges, it is being changed by an infinite amount almost immediately.

The very separation of the discussion to 1-particle and \(N\)-particle situations proves that the speaker doesn't really understand basic issues – he is making stuff up. He is inventing totally unscientific spooky interpretations about some undergraduate textbook material. Perhaps one page of the textbook (about 1-particle systems) is more spooky or less spooky than another.

But this difference is a pure fantasy. Quantum mechanics works for 1-particle systems, \(N\)-particle systems, and systems that cannot be described in terms of \(N\) particles at all. And all the novel features of quantum mechanics are completely universal and work in all these cases. 1-particle or \(N\)-particle systems are just ways to imagine some Hilbert spaces and some operators on them. But at the end, all infinite-dimensional Hilbert spaces are exactly isomorphic to each other. And all of them allow the same set of observables – linear Hermitian operators on these spaces. With complex enough gadgets, every quantum mechanical system with an infinite-dimensional Hilbert space may precisely emulate any other!

In a longer paragraph, they repeat the "inexplicable to" sentence and add a few comments about surprising phenomena including interference and erasers. But Dr Pawel Blasiak has built these systems out of classical physics, we are told. Numerous additional paragraphs repeat that "quantum mechanics is controversial" and he wants to get rid of the controversy by returning quantum mechanics to classical physics, and all this nonsense.

The article they are promoting is
Local model of a qudit: Single particle in optical circuits
in Physical Review A (zero citations). Blasiak promotes some childish redundant words such as a "qudit" [sic] and claims to have a "local realist" model of hidden variables that correctly describes the motion of a particle through some multiple slit interference experiments. Even if something like that were possible, it couldn't be important because we know that the number of particles may be greater than one and "two" is already enough to prove that local realist models cannot agree with the reality.

One may simply claim that a Bohmian picture is a "local realist" theory describing the interference experiments with one particle. But such a description is totally incompatible with any extension to particles with the spin and to \(N\) particles, not to mention other quantum systems. So it's demonstrably a misleading dead end in physics.

You know, even the states of a single particle inside a double slit experiments are entangled. Why is it so? Because to make sure that the total number of particles is \(N=1\) at all places behind the slits, we need a correlation between the number of particles \(N_U\) behind the upper slit and \(N_D\) behind the lower slit. The state where the particle has some amplitudes \(a,b\) to be at two places is really\[

\ket\psi = a\ket {0}_U \ket {1}_D + b \ket {1}_U \ket {0}_D.

\] You see that it's a nontrivial sum of two (more than one) tensor products, so it's an entangled state. With some Bohmian ideology, you can obfuscate the fact that even single-particle states may be represented as entangled states assuming a certain tensor decomposition of the Hilbert space.

Blasiak and similar people simply don't think in the quantum way. So they are really inventing non-existent and unscientific ways to divide the situations, in their futile effort to show that quantum mechanics doesn't apply somewhere – and maybe it doesn't apply anywhere.

On top of that, they really deny the basics of the scientific method. They no longer propose theories to explain and predict the observations which is what science should be doing. They are proposing simulations and they are deliberately vague about the question whether the simulations should be considered theories (the genuine rules how Nature works) or just some pedagogic tools to talk about theories and to play with theories.

I am sorry but true science of the "adults" cannot be ambiguous about such basic points. You either propose new theories for some phenomena or you don't. If you sell your paper as a "new theory" to some people while you use a language that allows you to claim that "you have never claimed to have a new theory" in a different environment, then you are a snake oil salesman.

All such would-be alternative theories have been understood by the top physicists to be impossible for more than 90 years.

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