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Quantum Physics Made Relatively Simple

 
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PostPosted: Mon Aug 24, 2015 5:34 am    Post subject: Quantum Physics Made Relatively Simple Reply with quote

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An émigré from Nazi Germany, Hans Bethe joined Cornell’s physics department back in 1935. There, he built a remarkable career for himself. A nuclear physicist, Bethe made key contributions to the Manhattan Project during World War II. After the war, he brought stellar young physicists like Richard Feynman from Los Alamos to Ithaca and turned Cornell’s physics department into a top-notch program. In 1967, he won the Nobel Prize for “his groundbreaking work on the theory of energy production in stars.”

As a tribute to Bethe, Cornell now hosts a web site called Quantum Physics Made Relatively Simple, where you can watch three lectures presented by Bethe in 1999.


http://bethe.cornell.edu/index.html

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PostPosted: Sun Aug 30, 2015 12:45 am    Post subject: Reply with quote

Damn. Three minutes into the first lecture, and I want to stick something sharp in my ears so I can't hear any more of it.

...

I tried a couple more minutes, but I'm done. Holy crap, he's bad. Laughing

But here's a great moment:
Quote:
Transistors replaced vacuum tubes. I suppose most of you are old enough to remember vacuum tubes, which were the predecessors of transistors.

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PostPosted: Tue Sep 15, 2015 1:54 pm    Post subject: Reply with quote

Maybe a Quantum Physics for Dummies is in order,
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PostPosted: Wed Sep 16, 2015 5:32 am    Post subject: Reply with quote

LOL I never actually watched any of it. Very Happy

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PostPosted: Tue Feb 21, 2017 5:24 pm    Post subject: Reply with quote

Well...this could be fun.
[[[though not really on topic---it doesn't seem to be simplifying Smile
First, the [relatively] easy/descriptive article on it,
Then the work by the guy with all the maths.

"George C. Knee, a theoretical physicist at the University of Oxford and the University of Warwick, has created an algorithm for designing optimal experiments that could provide the strongest evidence yet that the quantum state is an ontic state (a state of reality) and not an epistemic state (a state of knowledge)."


https://phys.org/news/2017-02-strongest-evidence-quantum-state-real.html

http://iopscience.iop.org/article/10.1088/1367-2630/aa54ab
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PostPosted: Sat Jun 24, 2017 7:11 pm    Post subject: Reply with quote

From Vraith's link:

Knee showed that a much better approach to this type of optimization problem is to convert it into a problem that can be studied with convex programming methods. To search for the best combinations of variables, he applied techniques from convex optimization theory, alternately optimizing one variable and then the other until the optimal values of both converge. This strategy ensures that the results are "partially optimal," meaning that no change in just one of the variables could provide a better solution. And no matter how optimal a result is, Knee explains that it may never be possible to rule out the epistemic view entirely.

"There will always be wriggle room!" he said. "Certainly with the techniques known to us at the present time, a small amount of epistemic overlap can always be maintained, because experiments must be finished in a finite amount of time, and always suffer from a little bit of noise. That is to say nothing of the more wacky loopholes that a staunch epistemicist could try and jump through: for example, one can usually appeal to retrocausality or unfair sampling to get around the results of any 'experimental metaphysics.' Nevertheless, I believe that showing the quantum state must be at least 50% real is an achievable goal that most reasonable people would not be able to wriggle out of accepting."

One especially surprising and encouraging result of the new approach is that it shows that mixed states could work better for supporting the ontic view than pure states could. Typically, mixed states are considered more epistemic and lower-performing than pure states in many quantum information processing applications. Knee's work shows that one of the advantages of the mixed states is that they are extremely robust to noise, which suggests that experiments do not need nearly as high a precision as previously thought to demonstrate the reality of the quantum state.

"I very much hope that experimentalists will be able to use the recipes that I have found in the near future," Knee said. "It is likely that the general technique that I developed would benefit from some tweaking to tailor it to a particular experimental setup (for example, ions in traps, photons or superconducting systems). There is also scope for further theoretical improvements to the technique, such as combining it with other known theoretical approaches and introducing extra constraints to learn something of the general structure of the epistemic interpretation. The holy grail from a theoretical point of view would be to find the best possible experimental recipes and prove that they are as much! That is something I will continue to work on."



There will be always be wiggle room, he says , but it sounds like a breakthrough may be here in settling the question, give or take a few years.
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PostPosted: Sat Jun 24, 2017 9:24 pm    Post subject: Reply with quote

+JMJ+

Vraith wrote:
Well...this could be fun.
[[[though not really on topic---it doesn't seem to be simplifying Smile
First, the [relatively] easy/descriptive article on it,
Then the work by the guy with all the maths.

"George C. Knee, a theoretical physicist at the University of Oxford and the University of Warwick, has created an algorithm for designing optimal experiments that could provide the strongest evidence yet that the quantum state is an ontic state (a state of reality) and not an epistemic state (a state of knowledge)."


https://phys.org/news/2017-02-strongest-evidence-quantum-state-real.html

http://iopscience.iop.org/article/10.1088/1367-2630/aa54ab


Cool beans. Thanx for posting this.

Though this subject matter lies largely outside my comfort zone, it seems to me that the either/or of the Ontic/Epistemic dichotomy is a badly-posed problem which would be better served by a both/and in the form of a simple duality.

Q: Ontic or Epistemic?

A: Yes.

Even the firstly-linked article seems to imply as much:

Quote:
… "There will always be wriggle room!" he said. "Certainly with the techniques known to us at the present time, a small amount of epistemic overlap can always be maintained, because experiments must be finished in a finite amount of time, and always suffer from a little bit of noise. That is to say nothing of the more wacky loopholes that a staunch epistemicist could try and jump through: for example, one can usually appeal to retrocausality or unfair sampling to get around the results of any 'experimental metaphysics.' Nevertheless, I believe that showing the quantum state must be at least 50% real is an achievable goal that most reasonable people would not be able to wriggle out of accepting." … [emphasis added]


----------------------------------------------------

I would think that a Hylomorphic interpretation (or some other Realist iteration) might be better positioned to deal with the insoluble problematics and potential frustrations engendered by the intersection of theory with reality than are those reductive approaches which seem to produce little more than endless, fruitless and oft-dispiriting debates.

Quote:
… That being said, there is a good bit of controversy as to what the experiments actually show. Certain interpretations of quantum mechanics do claim that there is a metaphysical indeterminacy in the quantum world, e.g., the photon's nature is in fact indeterminate, while other interpretations argue for more modest epistemic conclusions, e.g., the intrinsic nature of the photon is in principle beyond our ken, even if we can estimate its current state within a range of probabilities. There are also issues as to what counts as "observation." Using the split screen experiment again, in this case observation is made by applying a laser beam to a photon stream. As far as we know, it is an open question as to whether the laser beam in fact interacts causally with the photon stream in a way that explains the experimental results without the need to posit an actual indeterminacy in the quantum world, though such interaction is as yet unknown to us. We will not weigh-in on these issues, not only because they go beyond our meager scientific pay grade, but because our view is that quantum indeterminacy, even under a strongly metaphysical interpretation, should really be taken as good news for the overall plausibility of hylomorphism! Let's stipulate then that, per the metaphysical interpretations of quantum indeterminacy, the intrinsic natures of the most fundamental physical elements are in-themselves in superpositional states with respect to certain incompatible attributes. That is, quantum particles, when separated from broader determinate systems suffer certain indeterminacies.

To see why this stipulation poses no problem for the hylomorphist, begin by remembering that the hylomorphist argues that matter, when considered in precision from its compositional role in a determinate substance, is indeterminate among a certain range physical attributes, even otherwise essential attributes. The intrinsic indeterminacy of matter to contraries is what provides the potency for the sorts of change substances can undergo at various levels of composition, e.g., the indeterminacy of Smitty between running and walking is what makes it possible for him to pick up the pace, or the indeterminacy of certain amino acids between the different types of muscle tissue is what makes eating meat a means for muscle growth for various types of animals. Moreover, the broader the compositional role of a certain kind of matter, i.e., the more types of substances that it can compose, the greater its range of intrinsic indeterminacies, and ultimately the hylomorphist claims all material beings are the beneficiaries of the universal indeterminacy of prime matter. Thus, the hylomorphist is not at all surprised to find that as more fundamental types of matter are discovered so too are greater levels of intrinsic indeterminacy. Indeed he or she should expect as much. In other words, the "closer" we come to prime matter, the more we expect proximate matter to resemble prime matter's indeterminacy. …


Aristotelianism/Scholasticism has, again, never been more than a fleeting area of study, so I can't really speak to the issue in more than the most general of terms and can only defer to the specialists with regard to the rest.
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