## Proof Mooted For Heisenberg's Uncertainty Principle 158

Posted
by
Soulskill

from the he's-the-one-who-knocks dept.

from the he's-the-one-who-knocks dept.

ananyo writes

*"Encapsulating the strangeness of quantum mechanics is a single mathematical expression. According to every undergraduate physics textbook, the uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a subatomic particle — the more precisely one knows the particle's position at a given moment, the less precisely one can know the value of its momentum. But the original version of the principle, put forward by physicist Werner Heisenberg in 1927, couches quantum indeterminism in a different way — as a fundamental limit to how well a detector can measure quantum properties. Heisenberg offered no direct proof for this version of his principle. Now researchers say they have such a proof. (Pre-print available at the arXiv.) If they're right, it would put the measurement aspect of the uncertainty principle on solid ground — something that researchers had started to question — but it would also suggest that quantum-encrypted messages can be transmitted securely."*
## Fixed the summary (Score:2, Informative)

measurethe exact position and momentum of a subatomic particle the more precisely one knows the particle's position at a given moment, the less precisely one can know the value of its momentum.Fix.

## Re: You keep using that word... (Score:2, Informative)

I too found the title odd

[moot]

- adjective

1. open to discussion or debate

2. of little practical value

## Re:Fixed the summary (Score:4, Informative)

## Re: You keep using that word... (Score:5, Informative)

http://dictionary.reference.com/browse/moot [reference.com] says:

verb (used with object)

4. to present or introduce (any point, subject, project, etc.) for discussion.

5. to reduce or remove the practical significance of; make purely theoretical or academic.

So meaning 4 seems appropriate. Strange that a word simultaneously means to introduce it and to remove it from consideration, but it is a pretty old word I think so it has probably evolved quite a bit.

Origin:

before 900; Middle English mot ( e ) meeting, assembly, Old English gemt; cognate with Old Norse mt, Dutch gemoet meeting. See meet1

## Re:Uncertaintiy principle and Foruier Transforms (Score:2, Informative)

He means the location of the sonic event. If you think of sound as particulate (a series of events a la granular synthesis) then the frequency of each event and the location in time of each event satisfy a sort of uncertainty principle. It's because the FFT of sine * normal curve is sine * normal curve, but the width of the normal curve is conjugate in each case (the limiting case is sine * delta -> sine * 1). This width represents the "certainty" that the actual frequency or location in time is at the center point. It's a neat trick but it's not clear how or if it relates to QM, except via the mathematical equivalence. Once you start asking "what, then is h?" or "how does scalar amplitude relate to quantum phase" the illusion of relevance kind of vanishes.

## Re:Fixed the summary (Score:2, Informative)

Indeed. I don't know what crap "undergraduate textbooks" people use near the north pole, but here down under, the principle of Heisenberg is taught using _math_.

It has always been about measuring (not "knowing", the universe doesn't give a damn about what you know or don't know or it would forbid god from existing. Instead, it just hampers aquiring new knowledge of the full state vector ;p). And it has always been a nice mathematical, strictly quantified trade off between the precision you'll get out of one of the measurements being inversely correlated to the precision you'll get out of the other measurement because the product of the two must be at least half the reduced plank constant.