Talk:Bohm interpretation

Excised text:

Although for a long time considered a pariah among mainstream quantum physicists, Bohmian interpretation of quantum mechanics has recently gained ground due to the unequivocal experiment that has resolved the controversy Copenhagen vs. Bohm interpretation. Reactions from the physics community are yet to be seen. The paper on crucial experiment corroborating Bohmian interpretation (or, more correctly, shaking the Copenhagen orthodoxy) can be seen at Los Alamos site: http://xxx.lanl.gov/abs/quant-ph/0310096 (one could also consider http://xxx.lanl.gov/abs/hep-th/0304105 )

The quant-ph paper is hardly a description of a crucial experiment shaking the Copenhagen orthodoxy. It is a theoretical study comparing one model of the two slit experiment with another. There are slight differences between the results, but that could easily be due to differences between the inexact models used in each case. They do not claim that the differences are physical, and the experimental data fits both models. The main point of their paper was a demonstration of non-locality in the Bohmian interpretation. -- Tim Starling 23:53, Dec 4, 2003 (UTC)

---

Hmm...I'm not sure whether we're talking about the same thing. As I've read in the quant-ph article, the point is that non-locality is present even in the classical physics limit, ie. decoherence alone is not sufficient for explanation of quantum-classical "transitions", or "cuts" (in von Neumann's lingo). According to Copenhagen- there is not a single bit of quantum theory (ie. anything that characterizes QT as such) in the description of "classical world". And here, in Bohmian int.- it is.

Btw, as an aside: I'd say that the entire page on Bohmian int. is very poorly structured. Bohm's int. vs. Copenhagen (or quasi-Copenhagen as defined by Von Neumann and Dirac): ontological vs. epistemological; quantum potential/active information vs. ordinary wave-particle and probability waves; nonlocalicty vs. locality; wholeness vs. -I dont know how to call it: particulariness ?...is presented very poorly. In his posthumous book "The Undivided Universe", Bohm has (with Hiley, and, of course, in numerous previous papers) presented ellegant and complete description of the physical world. This description is in many aspects more satisfying than the prevailing one (and I'm not saying it's flawless or "perfect" since such notions are nonsensical). Just- the weigh of habit and pragmatism keeps people stuck to the old ways (they give good description- but so does Bohm). The only thing is that non-locality is almost "emotionally" unacceptable to the majority of working phsyicists. But- this is hardly an argument.

As I've said: this article "collapses" Copenhagen orthodoxy. And- the page on Bohmian int. really deserves (even without it) more. Now, he looks like some pop-guru, which is, probably, the perception of interested outsiders-but not the truth about a serious and testifiable physical theory.

Mir Harven

You've got to look closely at what they mean by the "classical limit". They don't mean using pre-quantum physics, like Zernicke decoherence or whatever. They just mean the probability density. See the paragraph under equation 14. They calculate this probability density using Bohmian mechanics, and observe that it is different to the probability density calculated using the standard decoherence picture. If you look at figures 1a, 2a, 2b and 2c, you see that the Bohmian mechanics result agrees with the standard result at the experimental scale. However I have to admit that I'm not familiar with Omnès' work. To me, the phrase "Omnès doubts that decoherence is the answer to loss of coherence" sounds like an oxymoron.

Please sign your entries with ~~~~, which is automatically converted to a name and a date. -- Tim Starling 01:40, Dec 7, 2003 (UTC)

Hmm...first, I apologize for a belated answer-I was lost in a maze of other, more mundane interests. But-are you sure you got their contention right ? I'll try to summarize what I've read from (and I hope not into) their article:

• their point is that Bohmian computation agrees with the experiment (addressed earlier, at the beginning of the "Results" chapter, just below eq. (14).). So, we must stress that it's the results of the experiment they're trying to explain, not just an exercise in one way of computation or another (or, more precisely, one formalism or another). To repeat: they try to reproduce the results of the experiment.

• they do it in two ways: Bohmian and "orthodox" (in a relaxed sense-but it is still orthodox; works by Zurek and others, i.e. references 2 and 3 in the article). Understandably, orthodox (or, better, ordinary) approach is within ordinary QM framework and doesnt employ specifically Bohmian concepts of quantum potential and active information. Just as an aside-one should mention that Bohmian approach is not new with regard to math formalism, but re interpretation of rather ordinary Sch. eq. (or, Ham.-Jac.), which simply gives a part Bohm had interpreted as quantum potential and developed a new view on QM with testifiable results. So, Bohm is (as anyone familiar with "The Undivided Universe" knows) not original re mathematical formalism (it's just a wave function in radial form, and Sch.eq. applied on it)-but in interpretation that denies central features of ordinary QM: no wave-particle dualism (electron is particle guided by quantum pot. field); no epistemological approach (i.e., quantum realism and ontology); and, most strikingly: non-locality vs. locality of ordinary QM (or any ordinary physical theory). Not to delve into intricacies further, what's at stake in this article is: there should be no non-locality in classical systems. And it is-according to the experiment and their Bohmian computation. But not in the ordinary decoherence framework. Look at this: "What it is remarkable is that this behavior even takes place in the case in which the coherence is completely lost (ô=0). This result is totally unexpected, and is due to the fact that the non–local behavior of quantum mechanics is preserved even in this case.This supports Omn`es’ suggestion that something else it is necessary, apart from decoherence, in order to make quantum mechanics exhibit a true classical behavior. In a Bohmian sense, even when interference eects are lost, still it is possible to distinguish between the result observed when the two slits are simultaneously opened, and those obtained from the sum of trajectories coming from each slit independently............

Conclusions. – By applying Bohmian mechanics to the paradigmatic two–slits experiment we have addressed a question raised by Omn`es about the possibility of decoherence theory to fully explain the appearance of classical behavior in a quantum system. Our results show that, although quantum statistics erases information about interference eects, there is still a strong non–local quantum correlation in the behavior of the system in the case of null coherence. This is due to non–locality in quantum mechanics, making that the probability density keeps information about the whole system. Such an information is “transmitted” to each particle, so that they “know” whether the other slit is open or not."

• or, in everyday speech: decoherence approach (i.e. ordinary QM) doesnt explain non-local behavior of classical systems (quot. "there is still a strong non–local quantum correlation in the behavior of the system in the case of null coherence.") This non-locality is the feature completely absent in ordinary QM, and peculiar to Bohmian mechanics. What needs to be stressed again: they point to the results of the experiments-not just their calculations. More simplistically: the keywords are CLASSICAL SYSTEM and NON-LOCAL BEHAVIOR (experimentally measured). And this is explained only (in this case) within the conceptual apparatus of Bohmian mechanics, and NOT decoherence.

• also- I do not see this corroborated by graphs, hence there is, IMO, discrepancy between their contentions and presented pictures.

Mir Harven 23:28, 13 Dec 2003 (UTC)

"It also differs in a few matters that are experimentally tested with no consensus whether the Copenhagen interpretation has been proven inadequate (and this inadequacy just glossed over due to inertia in physicist circles- not unlike the situation with cold fusion)" Excuse me, but isn't this a little bit biased of the author?

This page is a mess in explaining its subject. I edited it a little, tried to clarify. Still a mess, tho. 64.168.30.87 03:29, 24 Oct 2004 (UTC)

Critcism ? Or ignorance

Although personally I dont think Bohmian interpretation will bear much fruit-when criticised, it must be on fair basis. And, at least half of "criticisms" are, to put it mildly- lame. I've deleted, now, only the 1st point, since "inelegance" is personal preference, and, judging from the majority of opinion- this would be the last objection re Bohmian view. As for redundance-current physical theories are full of variables that are not directly verified and are props that may very well turn out to be just concoction: for instance, Higgs boson and dark matter. Other cristicism will be reviewed in due time, but, weaknesses of Bohm's interpretation cannot be addressed in such a manner, teeming with half-truths, since Copenhagen formulation abounds with even more "unacceptable" or concocted notions (anyone remember problems with classsical-quantum division, "healed" by Bohr's Correspondence pronciple-pure scholasticism, not provable at all). Bohm's "sin", if any, is that he was too timid and not radical enough. Mir Harven 12:57, 29 Oct 2004 (UTC)

category change

Linas removed this article from [Category:Quantum mechanics] and added [Category:Quantum measurement]. I reverted that edit, and then he reverted mine, with a note asking not to revert his change without discussion. OK, I'm here. Why did you remove this article from the Quantum mechanics category? --goethean 19:17, 14 May 2005 (UTC)

Yes, I'm puzzled myself. The articles under the rubric interpretation of quantum mechanics now fall under quantum measurement. Though not quite utterly absurd, this reclassification is quite idiosyncratic.--CSTAR