Quantum physics is a big topic in esotericism. Many esotericists are convinced that quantum physics can explain many esoteric phenomena that are inexplicable in a "natural" way. This is definitely not the case, but it is noticeable that some interpretations of quantum physics themselves sound surprisingly esoteric. For example, some interpretations assume that contradictions really exist in the field of quantum phenomena (Schrödinger's catKnapp: contradictions as part of reality). Or that the (material) world does not exist independently of immaterial consciousness (Bunge: Copenhagen interpretation), i.e. that the material world is dependent on an immaterial "observer". Also very esoteric is the idea that quantum phenomena, in contrast to the rest of natural science, should obey partly indeterministic, partly deterministic laws, that they are quasi "free of will". This is a dualistic idea that is otherwise strictly rejected in the natural sciences and leads to the probably fundamentally unsolvable measurement problem. There are no serious doubts about the results of quantum physics. But there are different interpretations of these results, some of which seem to be more esoteric than others. How can this be evaluated?

Interpretations of quantum mechanics as heuristics

If one speaks of quantum phenomena having contradictory properties or "behaving" indeterministically (Byrne: behaviour of electrons), this only applies to the subatomic realm. Moreover, the mysterious quantum effects, which contradict classical physics and are readily taken up by esotericism, cannot be observed in principle. At the moment of an "observation", i.e. a measurement, the mysterious "disappears", for example, classical logic applies again to quantum phenomena (Vaas: Der Widerspruch des Messproblems).

The mysterious quantum phenomena cannot be observed directly - nothing has ever been observed that contradicts classical logic, for example, and contains a contradiction. The mysterious quantum phenomena can only be inferred: on the basis of measurements made and mathematical formalisms, however, what has been observed can only be explained if different laws prevail in the field of quantum phenomena than in the "classical" field. Which laws are to be assumed depends on how one interprets measurements and mathematical formalisms.

While the mathematical formalisms of quantum mechanics are hardly ever questioned and probably cannot be questioned in any meaningful way, the results are interpreted in very different ways. These interpretations give quantum physics a meaning, try to show what "really", "in reality" happens in the realm of quantum phenomena (Honderich: Quantum Theory: Formalism or Interpretation).

However, to date there is no interpretation that is truly convincing and that does not involve problematic assumptions. None of the known interpretations seems to correctly reflect the reality in the field of quantum phenomena, but they seem to be pure heuristics, i.e. attempts to (temporarily) explain a phenomenon despite a lack of knowledge. As heuristics, many esoteric theories were also of great importance for a long time - but most esoteric theories could then be overcome by empirical research and the pointing out of contradictions from a scientific point of view, as will possibly also happen one day for some interpretations of quantum physics. For example, the well-known quantum physicist Anton Zeilinger writes in the journal Nature that it could well be that quantum theory will be replaced by a new theory in the future. Such a theory, however, would probably be even more radical than anything known today (Morsch: Quantum theory not final).

The Copenhagen Interpretation

The best-known interpretation of quantum mechanics is the Copenhagen interpretation. It is particularly popular with esotericists, theologians and philosophers (e.g. Knapp: Kopenhagener Deutung und Philosophie), as it diametrically contradicts classical physics in many areas (nice quote on this), but according to Rüdiger Vaas it is hardly actively defended by anyone today (Vaas: hardly anyone still defends the Copenhagen interpretation). 

The fact that the Copenhagen interpretation has become so widespread seems to have been less due to the fact that it is particularly convincing than to the fact that it satisfies ideological demands. Thus, quantum mechanics suddenly seemed to open a back door with which deterministic classical physics could be replaced by an indeterministic "new physics", and ideas of German Idealism that the world does not exist independently of human beings seemed to prove true. The latter idea has since receded into the background, even if it was advocated by the already quoted Anton Zeilinger and is possibly still advocated today (Zeilinger: World not without our observation). In many respects, it corresponds to esoteric ideas that like to see humans outside of nature or at least as dominating nature. 

Indeterminism as a premise

However, the idea of indeterminism is still very widespread. The fact that such indeterminism is not physically but ideologically based can be well illustrated by a quote from Valerio Scarani:

"Some people say that through quantum physics, chance has taken the place of determinism. This claim is "reasonable", but it doesn't hold up for long. Let's assume that you are a strict advocate of determinism (which is not true for me) and are convinced that all the details of the history of the universe were already set in stone and now just happened one by one. In particular, it was then also predetermined that they would "decide" to make a quantum measurement, the result of which was also already determined. As has already been mentioned, this view of things renders Bell's theorem irrelevant - the finished history of the world would then be a huge non-local hidden variable that explains everything. And that's the least of the inconveniences; the loss of any form of human freedom is a much more dramatic consequence. ... If you accept "indeterminism" for human beings, then you must also concede a kind of "indeterminism" to nature. Scarani 2007, p. 108.

What is exciting about this quotation is the matter-of-factness with which Mr Scarani presupposes indeterminism. For classical physics was strictly deterministic and thus excluded human freedom. From a physical point of view, a deterministic interpretation would therefore have to be preferred, since otherwise a dualism of determinism and indeterminism would arise. For many physicists, however, the temptation seemed too great that quantum physics could "finally" overcome the determinism of classical physics, which is why they gratefully accepted the indeterministic interpretation possibility such as that of the Copenhagen interpretation. That quantum mechanics cannot be indeterministic, however, is shown by the simple fact that it is not arbitrary, but extremely regular ("determinism or indeterminism).

"Brainwashing"

The fact that the Copenhagen interpretation was able to prevail is not based on a physical necessity but on a historical coincidence, as John Gribbin impressively describes on page 218 of his book "Schrödinger's Kitten and the Search for Reality" (1998):

"I have shown you where the Copenhagen interpretation will lead you if you follow it. And hopefully I have been able to convince you that it does not have a completely satisfactory explanation of quantum reality to offer. As I said, it owes much of its success to the historical coincidence that it was the first fully worked out interpretation and was championed by a strong personality. As early as 1976, Nobel Prize-winning physicist Murray Gell-Mann remarked: "Niels Bohr brainwashed an entire generation of physicists into believing that the problem had already been solved." That Bohr was so successful as a brainwasher was based in part on the fact that the only alternative interpretation that existed at the time was thrown out of the running by a calculation by the mathematician John von Neumann. In truth, von Neumann had been mistaken."

Since John von Neumann's error became known, there is no question that deterministic interpretations of quantum physics are possible. However, they are (at least so far) also not without fundamental difficulties. However, the fact that "classical" interpretations are obviously wrong is still hardly discussed today, but it is the reason why esotericism can so easily pounce on quantum physics. So this is not simply because esotericists have misunderstood quantum physics, but rather also because classical interpretations of quantum physics themselves contain esoteric and outdated philosophical assumptions (e.g. idealism, positivism). An anecdote can add a wink to this context: "It is said of the Danish physicist Niels Bohr (1885-1962) that he had a horseshoe hanging at the entrance to his house for good luck. A visitor is said to have asked him whether he believed such humbug and received the answer: "No, but supposedly it helps even if you don't believe in it."" (Franz M. Wuketits in Smalla 2011, p. 64.)