Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?

http://www.wired.com/2014/06/the-new-quantum-reality

by Anchor • 12 years ago

66 27 12 years ago

In case anyone is interested in the collective wisdom of the Hacker News community, you could look at the extensive discussion of this article from just over a month ago:

https://news.ycombinator.com/item?id=8554996

Earlier submissions, but with no discussion:

https://news.ycombinator.com/item?id=7964797

https://news.ycombinator.com/item?id=8034390

cmollis• 12 years ago

I know almost nothing about Quantum Mechanics, this seems to provide an interesting model for all particle behavior. I realize it's just a model, but why isn't anyone attempting to explain the actual 'fluid' part? What is that? They just refer to it as 'space and time'.. is this some form of pure energy field? is this the Higgs Field ? (or some other field) I realize that this might be an extremely stupid question. It seems consistent that matter (or any particle that has enough energy to become matter) would exhibit similar physical behavior as the experiments shown (like the pilot wave experiments in silicon oil,etc), but I'm sure my understanding is extremely naive.

gilgoomesh• 12 years ago

Fields in quantum mechanics really just describe the ways that the force fundamental forces (gravitational, electromagnetic, strong nuclear, and weak nuclear) travel around.

The double slit experiment, which this article focusses on, looks at photons. Photons, are carriers of electromagnetic energy – they're their own field.

The field though isn't really a fluid or medium – thinking about ripples moving across a pond won't help you. The field is just the distance over which the photon will travel. It's more about an area of opportunity for something to happen (e.g. in the event that something gets within range of the photon) rather than a big blobby mass actually hanging around in space.

There's no such thing as "pure energy" (although the fundamental forces are probably the simplest forms of energy). Energy is an emergent property of a system (it is a function of how things in one part of a system are arranged with respect to another part of the system).

macspoofing• 12 years ago

Isn't that common knowledge? First, there's no consensus among physicists on any particular interpretation, so right off the bat that should tell you that we are missing something really deep. Second, the Copenhagen interpretation itself is completely nonsensical. I'm convinced it is responsible for most of the millions made by Deepak Chopra.

gus_massa• 12 years ago

Second, the Copenhagen interpretation itself is completely nonsensical.

The problem is that most of the discussions about quantum mechanics interpretation are handwaving without enough linear algebra background. My two favorite questions before starting a discussion are:

* ) What are the eigenvalues of the matrix

  /  0 1 \
  \  1 0 /

* ) Why are they important for quantum mechanics?

raverbashing• 12 years ago

Well, the "shut up and do the math" interpretation of QM is very successful :P

I'm sorry I can't answer your question, I only learned about the Schroedinger's Equation

hessenwolf• 12 years ago

Oh, that's not fair. Answers, please.

analog31• 12 years ago

>>> First, there's no consensus among physicists on any particular interpretation, so right off the bat that should tell you that we are missing something really deep.

One thing it should tell you is that we have not been "interpreting quantum mechanics wrong this whole time" because we've made relatively little effort to arrive at an interpretation at all. During my time as a physics student, deeper philosophical issues weren't mentioned in class, and it seemed like the Copenhagen interpretation was grudgingly accepted as a de facto standard in order to just get on with life.

We knew there was some activity in the area of finding a more philosophically pleasing interpretation, and one or two seminar speakers talked about it, but it just wasn't a big deal. Many physicists even questioned the value or physics-ness of the pursuit.

Zigurd3• 12 years ago

It's an interesting macro-scale analogy. You can demonstrate interference in a double-slit experiment with oil drop.

But look what the article leaves out: You can't, as far as I can tell from the article, demonstrate the collapse effect of detecting which slit the particle passes through. In fact, you can always observe which slit the particle passes through, so measurement has no effect on the wave interference pattern.

If there is a "pilot wave" version of quantum mechanics, these experiments are only a suggestion of some of the mathematics. They appear not to be a macro-scale example.

snarfy2• 12 years ago

And just as measuring the trajectories of particles seems to “collapse” their simultaneous realities, disturbing the pilot wave in the bouncing-droplet experiment destroys the interference pattern.

Did we read the same article? Pilot wave theory has the same mathematics as quantum mechanics. It's a different interpretation of those mathematics - the probability wave is real and physical.

Zigurd3• 12 years ago

I read that. Note that it says "disturbing the pilot wave." That's not "measuring." The sentence is trying to draw an analogy with "collapse." But to do that you have to explicitly "disturb" the pilot wave.

In these droplet experiments, you can measure all you want without affecting the wave and the interference pattern. This might point to an analogous form of quantum mechanics. But it also could be just an interesting but incomplete analogy in classical physics.

shoegumfoot• 12 years ago

In fact, you can always observe which slit the particle passes through, so measurement has no effect on the wave interference pattern.

The first half of that sentence is true, while the second half is not (unless I am misinterpreting what you are trying to say).

Empirically, nobody has (yet) managed to come up with an experiment that measures which slit the photon/electron/other quantum object passes through AND preserves the wave nature of the double-slit effect. In other words, when you set up an experiment to measure which slit is traversed, the characteristic double-slit interference pattern disappears. Again, I'm talking about this purely in practice, or what people observe when they try to perform this experiment[1].

Theoretically, this is result is completely expected. To determine which slit the photon traversed, you must interact with the photon to observe it. Any observation has two results: First, you know the state of the quantum object. Second, the quantum object is in an eigenstate of whatever operator you used to observe it. Since you have forced the photon into an eigenstate, the interference pattern disappears.

[1] Not that you can still see two superimposed single-slit interference patterns, which might confuse some people into thinking they are seeing a double-slit pattern.

duncanawoods• 12 years ago

There was a recent quantum doc on BBC which was a pretty good watch. I think it mentioned the term pilot wave but the message they gave was that Bell test experiments proved that hidden variable interpretations were impossible and that the probabilistic reality of particles was undeniably true so you have to suck it up.

http://www.bbc.co.uk/iplayer/episode/b04tr9x9/the-secrets-of...

foobarbaz1234• 12 years ago

Only accessible in the UK ... :/

tachion• 12 years ago

You can access that content by installing something like Hola plugin in your browser, works quite well for watching 'Hey I've Got Bit More News For You' ;)

inclemnet• 12 years ago

the message they gave was that Bell test experiments proved that hidden variable interpretations were impossible and that the probabilistic reality of particles was undeniably true

This isn't actually the case - Bell's theorem and subsequent verification demonstrate only that a theory of local hidden variables cannot be successful - the local part means that faster than light information transfer doesn't occur. You're allowed to have a pilot wave interpretation if it's nonlocal.

I think this is actually a problem with these experiments - it's nice that they work, but we already knew pilot wave mathematics could describe quantum mechanics, with the caveat that nonlocality is necessary to explain everything. I don't think this nonlocality is (or can be) expressed in the fluid experiments, so presumably they can't actually replicate QM.

smortaz• 12 years ago

on YT: https://www.youtube.com/watch?v=KoPbsQeNc18

UhUhUhUh• 12 years ago

I would recommend David Bohm's "Wholeness and the implicate order." And Bohm in general: this guy was stripped from his US citizenship during the McC hysteria.

zeclec• 12 years ago

(OT) Brazil did not allow for dual citizenship at the time so when Bohm persued Brazilian citizenship he had to give up his US one.

brute2• 12 years ago

I dont get it.

Suppose I have a particle at coordinates (0,0) with some velocity in x-direction. Due to symmetry, the trajectory of a pilot-wave particle has to stay on the x-axis, while in QM the heisenberg uncertainty principle results in some momentum in y-direction.

Wouldn't you need to add some kind of imperfection to disturb the pilot-wave in order to reproduce the probabilistic results?

TylerJay• 12 years ago

One of the main objections to the pilot-wave theory of QM is that it brings us back to the idea of a "luminiferous aether" that was famously disproved by the null result of the Michaelson-Morley experiment. What would the substrate be? The article gives a very brief hand-wavy mention to it being "space-time" and I've heard this before, but I have yet to hear even a good suggestion for how this might work.

A related problem is that both De Broglie's and Bohm's pilot-wave models leave open the possibility of "empty waves" that carry no momentum or energy and are not related to any particles. Even if we assume that it is space-time through which they propagate, this gives us another piece of math that we need to just throw away, similar to the non-observed probabilities after state collapse, which runs counter to the goal of creating a formalism where the math corresponds to something real in the universe(s).

brute2• 12 years ago

One of the main objections to the pilot-wave theory of QM is that it brings us back to the idea of a "luminiferous aether"

No it does not. We already have the Schrödinger field, without any notion of an aether. In fact the whole quantum field theory is all about fields and does not require it.

Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?

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