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(All Voices)   Scientists cast doubt on infallibility of Heisenberg's Uncertainty Principle, which holds that it is impossible to measure anything, since the act of measurement disturbs the object and thus, the measurement   ( allvoices.com) divider line
    More: Interesting, Heisenberg, doubts, quantum mechanics, quantum cryptography, physics, relativity, Physical Review Letters  
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3607 clicks; posted to Geek » on 08 Sep 2012 at 3:09 PM (5 years ago)   |   Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»

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2012-09-08 01:23:18 PM  
4 votes:
Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.
2012-09-08 06:56:08 PM  
2 votes:
nobody seems to bother to click through links.

From Synopsis: The Certainty of Uncertainty

... If the observer affects the observed, how can one even make such a measurement of the disturbance of a measurement? Rozema et al. use a procedure called "weak" quantum measurement: if one can probe a quantum system by means of a vanishingly small interaction, information about the initial state can be squeezed out with little or no disturbance. The authors use this approach to characterize the precision and disturbance of a measurement of the polarizations of entangled photons. By comparing the initial and final states, they find that the disturbance induced by the measurement is less than Heisenberg's precision-disturbance relation would require. ...
2012-09-08 03:33:17 PM  
2 votes:

Here's a wonderful example: this study provides experimental support for the HUP. That's right- this study demonstrates that the Heisenberg Uncertainty Principle does exactly what we think it does, but instead, everybody's running around going, "OMG! It's not uncertain at all!"

Once upon a time, there was this thought that it was the act of measurement that caused uncertainty. Since measuring a particle requires interacting with it, and interacting with it changes its state, this makes intuitive sense. Like most intuitive ideas in QM, it's also wrong. It's been proven wrong mathematically for decades, but this provides experimental evidence that the measurement disturbance relationship is not the cause of uncertainty.
2012-09-08 02:16:48 PM  
2 votes:

Dafodude: Tigger: Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.

I'm a layman here, but I'm guessing that the paper just challenges certain assumptions about the principle. No matter (ha!) what, you still have to rely on some kind of interaction to make the measurement, which is always a two-way street, right? And that the precision is still limited to the wavelength involved, and the higher the precision you want, the shorter the wavelength and therefore the more energetic of an interaction. Yeah, this headline is a bad explanation - the measurement doesn't disturb itself, it's just that by measuring part of the state information of a particle you have to disturb the rest of it. Am I getting even close?

Wish I had access to the actual paper.

Not very close no! The Heisenberg uncertainly principle doesn't state that you can't measure it because you'll disturb the measurement. It states that there is a limit to what is functionally knowable about the position of a particle in the universe because that particle has a waveform. As a result it is not in any particular place it is merely an uncollapsed probability function before you measure it.

If you actually are interested I would recommend "How to Teach Quantum Mechanics to Your Dog" as an excellent book that doesn't require any specialist knowledge.
2012-09-08 05:23:19 PM  
1 vote:
i.imgur.comView Full Size
2012-09-08 04:44:29 PM  
1 vote:

whatshisname: Hence you can't know both at once.

Yes you can. But only to a certain limit of precision. Which is true of every measurement; every measurement has a finite precision. That's why the concept of "significant figures" exists. No measurement can ever be said to be 100% accurate- it's accurate to a certain level of precision. HUP just sets some lower bounds on how precise a specific pair of measurements can be.
2012-09-08 04:40:27 PM  
1 vote:
So we may someday be able to construct a Heisenberg... compensator?
2012-09-08 04:17:45 PM  
1 vote:

whatshisname: You can't know both their position and momentum.

Close: you can't know both momentum and position to an arbitrary precision. The amount of uncertainty in the measurement has a floor- there will always be a minimal level of uncertainty. That level is ħ / 2 (ħ being planck's constant). You can know both position and momentum, but only to a point- at some point you have to sacrifice precision.
2012-09-08 03:33:36 PM  
1 vote:
Click through to TFA linked by TFA. It's not questioning the "true" uncertainty principle, the one bounded by Planck's constant. It's just challenging the limits of the "measurement-disturbance relationship," where uncertainty beyond the physical minimum is introduced by the act of measurement. The only reason Heisenberg's name came up is because, and I did not realize this, Heisenberg himself had initially proposed such a relationship as the reason for the uncertainty that now bears his name.
2012-09-08 12:42:15 PM  
1 vote:
Say my name.
2012-09-08 12:16:01 PM  
1 vote:
From Schrodinger's Cat (an epic poem):

Shine light on electrons,
You'll cause them to swerve!
The act of observing,
Disturbs the observed!
2012-09-08 12:10:48 PM  
1 vote:
which holds that it is impossible to measure anything

That's certainly true. I tried to measure something today with a yardstick; but as I got the yardstick near, it fell over and broke. Quantum mechanics works in mysterious ways.
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