People often perceive quantum mechanics as an ad hoc collection of ideas because it is a highly complex and abstract field that challenges our everyday intuitions. It is true that the field has multiple interpretations, and this can lead to confusion and the perception that physicists and mathematicians are still "guessing" about its principles. However, this is not a reflection of a lack of understanding, but rather an indication of the rich and deep nature of the subject.

There are several reasons why people might have this perception:

Counterintuitive concepts: Quantum mechanics deals with phenomena at the atomic and subatomic levels, where the behavior of particles can be very different from what we observe in the macroscopic world. Concepts like wave-particle duality, superposition, and entanglement can be hard to grasp and often seem bizarre.

Multiple interpretations: As you mentioned, there are several interpretations of quantum mechanics, such as the Copenhagen interpretation, the Many-Worlds interpretation, and the de Broglie-Bohm interpretation, among others. Each offers a different perspective on the nature of reality and the behavior of quantum systems, but none are universally accepted as the "correct" interpretation. This can lead to the impression that the field is uncertain and speculative.

Mathematical complexity: Quantum mechanics is built on sophisticated mathematical tools and models, which can be challenging even for those with a strong background in mathematics. This complexity can make it difficult for non-experts to appreciate the rigor and coherence of the field.

Ongoing research: Despite its remarkable successes, quantum mechanics is not yet a complete theory. Researchers continue to investigate open questions and explore new ideas to better understand the quantum realm. This ongoing research can give the impression that the field is still a work in progress.

So, while quantum mechanics is indeed a complex and multifaceted field with multiple interpretations, it is not a random ad hoc collection of ideas. Rather, it is a well-established and highly successful branch of physics that has provided us with profound insights into the fundamental nature of the universe. Its ongoing development and open questions are a testament to the richness and depth of the subject, as well as the dedication of the scientific community in seeking a deeper understanding of the quantum world.

Regards,

The principles are understandable, explained exactly the same way in

a huge number of QM books. In practice you dont worry about "interpretations", you simply learn how to do QM calculations.

Its mostly philosophers, or those with little experience, who will be fussy.

Translate all your quantities into operators, write out the Hamiltonian,

solve H psi = E psi,

if time independent, get the spectrum of values for E and the eigenfunction for each; analyze which operators commute with each other (thats the set that can be measured together), etc

In any case psi is only good for one thing, psi* psi, a probability density.

Any psi is undetermined then by some phase factor as in psi exp(i alfa), for example -psi means the same as psi. So how could it mean something physically? Its only u|se to describe the wave.

This is because people have tried to answer the intricate physics of quantum measurements by simple postulates, which leads to various proposals, all wrong in principle. I worked on this issue for 25 years starting from a setup where the z-component of a spin 1/2 is measured by an apparatus which consists of an Ising magnet coupled to a bath. The quantum state emerges as a state of your best knowledge. See arXiv 1107.2138 (200 pages, >> 500 equations)

True, the discourse of QM often seems only approximate, its hard to

make it fool proof accross all the problems it enconters. Therefore some things come accross as too orthodox.

On the other hand the purpose is to make something not too rigid, rather more flexible to absorb particular cases and possible generalizations. If

you make it too general, it sounds inspecific.

Therefore there is a collection of some loose general rules to use.

Mostly examples of things already settled in the past.

Juan Weisz We went to the core of a measurement, considering "the simplest model" for what happens in a laboratory measurement. Even then, the analysis was intricate. Do you know a simpler but rich enough model?

In the past there were many viewpoints, nothing was settled. Ours was not formulated before with all its subtleties.

We started from the quantum formalism without interpretation, found that cat terms vanish dynamically and that the Born rule emerges for ideal measurement. Our emerging viewpoint is that the density matrix describes our best knowledge about the set of systems considered. It was not formulated before with all its subtleties.

Hi Th.M.

I think that when experimentalists read Q.Theory they think theorists are really simplistic guys.

Say they read "On measurement the system jumps to one of the set of possible eigenstates" actually

interpretable as just one eigenstate. Then they usually clarify that they turn up with some

relative probability given by the square modulus of amplitudes. What they dont usually say is that in

many cases you dont know what these amplitudes are.

Well, when you observe a Hydrogen atom spectrum, you get a whole bunch of discrete lines, each

actually transition between two eigenstates, so what you finally get after an analysis, is a

whole bunch of eigenstates

together. It seems the wording is more appropriate say to a two level spin problem, either up or down.

Then there are many particular calculations, which can give you the same results as a Q one, and you come out

with a feeling that the whole formalism may be extraneous. This can happen say with the frequencies of simple molecules under vibration.

Anyway, I think a well rounded formation of a physicist should included many hours of experiment

along with theory. This can temper certain flawed ideas that may come out of the theory alone.

However the best experimentors also know the theory.

A good analysisof some given experiment usually requires going over it from both sides.

Do we really see what we expect to see or something else? is a comon question.

Regards, Juan