Quantum Physics / Quantum Mechanics

[Q.E.D.]

I haven't been able to dig up a pre-print (or access the actual journal article) yet. From what I gather from the pop science articles, this paper discusses an experiment which uses nonlinear optical effects to gather information about a momentum probability distribution without sacrificing information about particle position. The Heisenberg Uncertainty Principle requires that certain complimentary pieces of information cannot be mutually extracted from a physical system. A particle cannot give off position information without stealing some information about momentum.

When a particle is at a definite exact position, quantum mechanics predicts that it can have any momentum whatsoever. This research shows that a particle with a very precise position will have a momentum obeying a reasonable probability distribution. In my view this may prove to be a small victory for physical realism (the philosophical position that physical reality exists independently). I'll keep looking for more information.

[Grames]

What is a reasonable interpretation of these results?

Even Heisenberg admitted it was possible to get around the Uncertainty Principle by taking measurements of position and momentum at different times and using a back plotting technique. Using averages and making inferences as in this experiment are an implementation of that technique. The Uncertainty Principle remains inviolate.

On one level, the experiment appears to violate a central rule of quantum mechanics, but Professor Steinberg said this was not the case.

He explained to BBC News that "while the uncertainty principle does indeed forbid one from knowing the position and momentum of a particle exactly at the same time, it turns out that it is possible to ask 'what was the average momentum of the particles which reached this position?'" .

"You can't know the exact value for any single particle, but you can talk about the average."

An average has an error bar, but it does not correspond to any particular particle.

Edited June 3, 2011 by Grames

[Dormin111]

*** Mod's note: merged with earlier topic. - sN ***

 

A facebook "debate" (a bunch of anti-objectivists insulting a youtube video) cropped up on my newsfeed today over the following video:

 

 

I have not watched the video yet and will be unable to for a while but in it David Harriman claims that Quantam Physics is mystical and invalid. Being someone who knows next to nothing about quantum physics and only slightly more about physics, can someone succinctly summarize on Harriman's arguments and elaborate if necesary. The general response from the FB crowd was to appeal to authority (ie. how can these philosophers challenge hard science) but I did not know enough on the subject to formulate a proper response.

Edited June 24, 2015 by softwareNerd
Merged with an earlier topic

[bioengine]

I have not watched the video yet and will be unable to for a while but in it David Harriman claims that Quantam Physics is mystical and invalid. Being someone who knows next to nothing about quantum physics and only slightly more about physics, can someone succinctly summarize on Harriman's arguments and elaborate if necesary. The general response from the FB crowd was to appeal to authority (ie. how can these philosophers challenge hard science) but I did not know enough on the subject to formulate a proper response.

 

Harriman doesn't challenge "hard science".  I don't think he challenges the actual results of experiments, just the interpretations of the twentieth century physicists.  Because the results of their experiments are confusing they say that a particle exists in every possible state with no particular identity until you try to observe the particle at which time it chooses an identity.  Some of the physicists go further and claim that the moon isn't there unless you are actually looking at it.  So they obviously don't believe in the primacy of existence or apply it to how they interpret their experiments.

[Grames]

A facebook "debate" (a bunch of anti-objectivists insulting a youtube video) cropped up on my newsfeed today over the following video:

It is not up to philosophy to dictate what the science of physics must discover. On the other hand, it is invalid to base one's philosophy on the latest theory in physics. Because physics requires logic and inference (philosophical tools) to be valid for any of its discoveries to be considered proven, a physics that attempts to refute logic and inference is self refuting. Logic entirely rests on the law of identity being valid, so Harriman can be construed to be correct.

But in this presentation Harriman gives the appearance of being "off his rocker". He could legitimately attack the various quantum mystics out there who start with a prior philosophical commitment to mysticism and try to use quantum mechanics as a justification. Wild interpretations on what quantum physics means, especially abuses of the Heisenberg Uncertainty Principle or the Copenhagen interpretation or the many worlds interpretation, are rampant outside of physics. Few actual physicists indulge in those wild interpretations however, so to me he comes off as attacking a strawman (an opponent that does not exist) when he repeatedly identifies physicists as the bad guys.

As far as physics goes Harriman's argument is pointless anyway, he is re-fighting a war that is long over. "Quantum Mechanics" is an introductory course to quantum phenomena, while the real theory physicists employ will be a quantum field theory. For example the de Broglie–Bohm theory, also called the causal interpretation, in a quantum field theory version.

Edited May 19, 2013 by Grames

[Harrison Danneskjold]

For example the de Broglie–Bohm theory, also called the causal interpretation, in a quantum field theory version.

Do you know how most physicists feel about De Broglie-Bohm?  I've only recently heard of it (while attempting to find the flaws in the Copenhagen Interpretation) and it amazes me that it doesn't seem to be discussed very much, whenever QM is explained to laymen.

[Grames]

Do you know how most physicists feel about De Broglie-Bohm?

I do not know the relative popularities of the various plausible theories.  

[Plasmatic]

David Harriman has shown in his lectures that the common response, " But thats not what physicist really think", is false. He demonstrates the actual position of the founders of the copenhagen interpretation is exactly that.

Edited May 19, 2013 by Plasmatic

[Grames]

Yeah, but "the founders of the Copenhagen interpretation" are a fringe element nowadays.

[Plasmatic]

Personally, I think the real beef is in field ontology.

Edited May 19, 2013 by Plasmatic

[Dormin111]

Yeah, but "the founders of the Copenhagen interpretation" are a fringe element nowadays.

 

I am currently taking an introductory Astrophysics course at the University of Chicago, and we are taught that the Copenhagen Interpretation is correct.

[StrictlyLogical]

Quantum mechanics is valid insofar as the mathematics does describe how very small things behave and they do not behave as classical particles.

 

Interpretations of Quantum mechanics which invoke consciousness to "observe" and "cause" wavefunction collapse are incorrect.

 

 

Physcists have not turned to the DeBroglie Bohm theory because it invokes additional physical things which, since it cannot be measured independently, is superfluous.  Using Occam's razor, most physicists turn to the purely mathematical model of a system characterized ONLY by the outcomes.  Some like to think seriously about various "interpretations".

[Eamon Arasbard]

 

Interpretations of Quantum mechanics which invoke consciousness to "observe" and "cause" wavefunction collapse are incorrect.

 

I don't think this position is advocated by any actual physicist, or ever has been, although I'm sure there are a few New Age mystics who would make that claim. What the "collapsing wavefunction" model would mean is that a particle has an indeterminate wavefunction until it interacts with another object in the macroscopic world. This would not, strictly speaking, be a human consciousness under any plausible circumstance. It would be the piece of computer equipment used to measure the position and velocity of a particle.

 

A wave/particle does also have definite properties before it is "observed" -- namely, a range of probability of where it might be, and how fast it might be going, defined by a specific set of mathematical equations which are equivalent to a wave function. Once it has interacted with the measuring equipment, the mathematical equations change to something more similar to a particle, but it is probable that, once the equations involved are properly understood, they will resolve into something which the human mind can interpret more easily.

 

At least that's my understanding of it. It's been a while since I've picked up a physics book.

[frank harley]

Quantum mechanics is valid insofar as the mathematics does describe how very small things behave and they do not behave as classical particles.

 

Interpretations of Quantum mechanics which invoke consciousness to "observe" and "cause" wavefunction collapse are incorrect.

 

 

Physcists have not turned to the DeBroglie Bohm theory because it invokes additional physical things which, since it cannot be measured independently, is superfluous.  Using Occam's razor, most physicists turn to the purely mathematical model of a system characterized ONLY by the outcomes.  Some like to think seriously about various "interpretations".

De Broglie/Boem was proven wrong by the application of Bell's Theorem. The behavoir of photons--including 'spooky action at at distance' --are predictably consistent; therefore no hiden variable is needed.

[frank harley]

I don't think this position is advocated by any actual physicist, or ever has been, although I'm sure there are a few New Age mystics who would make that claim. What the "collapsing wavefunction" model would mean is that a particle has an indeterminate wavefunction until it interacts with another object in the macroscopic world. This would not, strictly speaking, be a human consciousness under any plausible circumstance. It would be the piece of computer equipment used to measure the position and velocity of a particle.

 

A wave/particle does also have definite properties before it is "observed" -- namely, a range of probability of where it might be, and how fast it might be going, defined by a specific set of mathematical equations which are equivalent to a wave function. Once it has interacted with the measuring equipment, the mathematical equations change to something more similar to a particle, but it is probable that, once the equations involved are properly understood, they will resolve into something which the human mind can interpret more easily.

 

At least that's my understanding of it. It's been a while since I've picked up a physics book.

The most famous Physicist who took a decidedly mentalist view of his science was Wigner, who said that the confluence between math (a mental construct) and observable data was \far too close to be naturally coincidental. For him, our mind was indeed a causal element....

[frank harley]

I don't think this position is advocated by any actual physicist, or ever has been, although I'm sure there are a few New Age mystics who would make that claim. What the "collapsing wavefunction" model would mean is that a particle has an indeterminate wavefunction until it interacts with another object in the macroscopic world. This would not, strictly speaking, be a human consciousness under any plausible circumstance. It would be the piece of computer equipment used to measure the position and velocity of a particle.

 

A wave/particle does also have definite properties before it is "observed" -- namely, a range of probability of where it might be, and how fast it might be going, defined by a specific set of mathematical equations which are equivalent to a wave function. Once it has interacted with the measuring equipment, the mathematical equations change to something more similar to a particle, but it is probable that, once the equations involved are properly understood, they will resolve into something which the human mind can interpret more easily.

 

At least that's my understanding of it. It's been a while since I've picked up a physics book.

One normal way of understanding particle behavior of photons is by matrix algebra. This was first developed, btw, by Heisenberg, et cie in 1925, I believe. Wigner and Heisenberg developed further, nore complex matrices, the D & S models.

 

Present models refer more to Feynman's Path Integral...

 

The problem is that the math of particle description simply doesn't 'talk' to that of wave; Copenhagen, then, is far more a pragmatic reality than a philosophical posture.

[Dormin111]

To clarify, my professor did not say that consciousness affects reality, but he did say that time-space is metaphysically indeterminate for subatomic particles, and he explicitly referenced the Copenhagen theory.

[Harrison Danneskjold]

1. Indeterminacy of any sort is empirically unverifiable.  Since "random" is the negation of any pattern, as such, it can never be proven to exist; we can only disprove various patterns.  http://en.wikipedia.org/wiki/Quantum_indeterminacy
2. Quantum Indeterminacy is logically derivative from determinism; you cannot define "random" except by reference to a pattern, in the same way and for the same reasons that you cannot define "nothing" except by reference to "something".  This makes its assertion one gargantuan, conceptual larceny. http://en.wikipedia.org/wiki/Counterfactual_definiteness
3. The negation of any sort of pattern, as such, is a negation of the Law of Identity which logically descends from the Primacy of Consciousness implicit in Heisenberg's Uncertainty Principle.  http://en.wikipedia.org/wiki/Uncertainty_principle
4. Heisenberg's Uncertainty Principle implicitly denies the Primacy of Existence when it refers to subatomic particles, in the absence of any observer, as physical "information".

It may well be a valid formula (I doubt it would still be used if it were not empirically valuable) but its widespread interpretation amounts to an inversion of Consciousness over Existence which inevitably leads to the denial of the Law of Identity which can only occur as a Reification of the Zero- because to be is to be something.

And at the root of all such epistemological contortions, in their motivation, is fear:

http://en.wikipedia.org/wiki/Static_interpretation_of_time

[frank harley]

To clarify, my professor did not say that consciousness affects reality, but he did say that time-space is metaphysically indeterminate for subatomic particles, and he explicitly referenced the Copenhagen theory.

Time space is indeed determinate down to h/2, per the Heisenberg. As to 'metaphtysically' determinate, welll....uhhh...h/2 means workable down far beyond the level of the smallest subatomic.

[frank harley]

 

1. Indeterminacy of any sort is empirically unverifiable.  Since "random" is the negation of any pattern, as such, it can never be proven to exist; we can only disprove various patterns.  http://en.wikipedia.org/wiki/Quantum_indeterminacy
2. Quantum Indeterminacy is logically derivative from determinism; you cannot define "random" except by reference to a pattern, in the same way and for the same reasons that you cannot define "nothing" except by reference to "something".  This makes its assertion one gargantuan, conceptual larceny. http://en.wikipedia.org/wiki/Counterfactual_definiteness
3. The negation of any sort of pattern, as such, is a negation of the Law of Identity which logically descends from the Primacy of Consciousness implicit in Heisenberg's Uncertainty Principle.  http://en.wikipedia.org/wiki/Uncertainty_principle
4. Heisenberg's Uncertainty Principle implicitly denies the Primacy of Existence when it refers to subatomic particles, in the absence of any observer, as physical "information".

It may well be a valid formula (I doubt it would still be used if it were not empirically valuable) but its widespread interpretation amounts to an inversion of Consciousness over Existence which inevitably leads to the denial of the Law of Identity which can only occur as a Reification of the Zero- because to be is to be something.

And at the root of all such epistemological contortions, in their motivation, is fear:

http://en.wikipedia.org/wiki/Static_interpretation_of_time

 

Please remember that Heisenberg himself did not derive any 'uncertainty' principle. All the equation says is that measurement (dT/dD) can go down to h/2. That it can't go lower means there 's nothing smaller in nature than a photon (wave) divided by 2.

 

Yet to a working Physicist, the fact that the measurement can go this precise is a holy grail of opportunity, not a stopligh of 'indetermanacy. For more, please see 'Bose/Einstein equations. Bosons, or massless particles that emit energy because of theie whole spin, can be studdied and classified.

 

'Indetermanancy', then, is a set of interesting metaphysical issues that are extrinsic to how physics is really done.