Why I hope QM is incomplete

DennisN

Btw,
Well, this is a little tricky question, you know . I could agree with you in some sense, but on the other hand disagree. Where do we draw the line between microscopic and macroscopic?
In a sense, yes, "classical" macroscopic physical behavior can be seen as emerging from the behavior of miscroscopic systems (gravity is still a problem though, but that's another story). I'll give you some examples of "macroscopic QM" (there are more);

* Superconduction (e.g. SQUID)
* Superfluid Helium (clip)
* The double-slit experiment is a macroscopic demonstration (clip)
* This is a macroscopic demonstration (clip) of the Uncertainty Priciple.

Bonus material: The color of gold is a demo of microscopic relativity, pretty interesting I think + also the liquidity of mercury. Provided by me just to show macroscopic results of microscopic behavior.

(see also Macroscopic quantum phenomena)

DennisN

I would personally choose other literature (at least at first). I see no reason to cloud one's objectivity by introducing humans as special. But it's my personal opinion of course. A quite interesting question (from a psychological perspective IMO) is why some people seem to resort to the human perspective when discussing QM. It seems... unusual. We don't seem to need any human perspective when discussing, let's say, thermodynamics or relativity.
No, you are not alone . But I would personally not call it absurd, but interesting, because:
I agree with atyy.
Yes!

mfb

I would like to add Bose-Einstein condensates to the counterexamples of DennisN.
That literature is bad then, unless this option is just mentioned as one of many interpretations (and I don't think it has many supporters).
There are interpretations where the time-evolution of the universe is deterministic, in particular the de-Broglie-Bohm theory and many worlds.

Superpositions exist in all interpretations in some way. Otherwise, you could not perform double-slit experiments.

No, it does not fit to experiments. You can decide what you want to measure even after the photon passed the slit(s).

To get an interference pattern, this information has to be destroyed in a very fundamental way - in a way not even a rock could "observe" it.

The_Duck

Unfortunately there's a lot of nonsense written about QM. Your instincts that human consciousness should not be special are correct. Anyone who tries to associate QM with human consciousness is talking nonsense.

No, many people have an instinctive reaction against non-determinism. But keep in mind that the universe doesn't particularly care what you find absurd.

All we can do is look at the world and try to describe what we see, and what we see is that it is possible for things to be in "superpositions" of different states.

Classical mechanics arises gradually from quantum mechanics as you consider larger systems, in the same way that Newtonian mechanics arises gradually from special relativity as you consider slower speeds.

DennisN

I also forgot the Tunnel diode, which makes use of quantum tunnelling.

bhobba

Then the book to get is - Quantum Mechanics - A Modern Development by Ballentine:
http://www.amazon.com/Quantum-Mechan.../dp/9810241054

An observation is any device capable of recording an outcome - it has nothing to do with a conscious observer. But don't take my word for it - it's all explained in full detail in the reference above.

Thanks
Bill

micky_gta

I do not understand your answer to my question?

my question: "How would you explain the double slit experiment where a 'measuring device' was left on but the information leaving the measuring device was not allowed to reach its destination and viewed (by humans) AND STILL resulting in a an interference pattern? "

People argue that its the measuring devices that causes the double slits to appear instead of an interference pattern when clearly experiments have shown that its not. Its where the information ends up and 'who' knows about it.

mfb

If the environment knows about it (and we get decoherence), it is a measurement (and we destroy interference), otherwise it is not (and we get interference). It does not matter if a human, a dog, or a rock might receive the measurement result.

In other words, if you get an interference pattern, your measuring device did not really measure the position of the particle - it might have interacted with it, but there is no measurement result.

DrChinese

No one knows "why" the laws of physics are as they are. But being "reasonable" is not a requirement of those laws. Quantum mechanics is a great theory and it is very useful. The implications of it are subjective to each person, but it is certainly considered strange by most. That does not stop science from moving forward.

Many experiments have been performed to shed more light on things. So far, the basic theory from circa 1927 remains intact. You mentioned Bell's Theorem, this is a very important stepping stone to answering your original question.

DrChinese

The above is incorrect for a couple of reasons. If it is not observed by a human, we don't know what happened (interference or not). On the other hand, there is no evidence at all that human observation yields any special results - ie the opposite of what you are saying.

bhobba

Why is that? What is so special about a human? Why, for example, if the outcome was recorded in a computer wouldn't knowledge of what had happened exist just as well as if it was observed by a human? Would not wave function collapse occur exactly the same? Indeed once decoherence has occurred regardless of if an outcome has been recorded or not, has not, for all practical purposes, an observation occurred? As far as I can tell once decoherence has occurred and a pure state has been transformed into an improper mixed state then in effect an observation has occurred - at least for all practical purposes - by which I mean no experiment can tell otherwise.

I am very uneasy about this introduction of human observers into the theory even in saying things like you said above as I think it introduces unnecessary obfuscation. I know you are not advocating consciousnesses causes collapse but why introduce issues of 'human' observation at all?

Thanks
Bill

DrChinese

I think you misunderstood my comment. Logically, we NEVER know the result of ANY unobserved measurement. For if you did, you must have observed it! This has nothing to do with QM, it is just logic.

As to QM, there is NO element of it which says that there is anything special about human observers, consciousness, or similar. There are those who say there is that element, but that is just their own opinion. It is not generally accepted science.

Generally, in the double slit experiment, there is no interference pattern if it was even POSSIBLE for to know which slit even if the human didn't bother to try and collect that information. So I conclude that the physical presence of a conscious observer is NOT a primary determining factor in decoherence.

Maui

Isn't this a similar case to the HUP and its dependence on what can be known about noncommuting observables, which introduces knowledge of the observer into where you clearly hate to see it? When people say knowledge, they always mean knowledge of the observer as there is no other knowledge.

bhobba

Now Dr Chinese clarified what he meant I am cool with it. But, as a point of semantics, I personally do not agree with your view of 'knowledge'. IMHO knowledge exists once it is recorded - not when an 'observer' knows about it. But this is a philosophical issue not of any real value IMHO - I simply mention it as something that's open to debate.

Thanks
Bill