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Physicists demonstrate new way to violate local causality

phys.org

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Re: Physicists demonstrate new way to violate local causality

#41

Post by pavement »

joeberon wrote: post #12

Wow the comments here are weak. Honestly surprised that the physics knowledge is so low here...

Software developers are not physicists. Software developers aren't even mathematicians, although many are enamoured with related concepts.

To grasp the difference between the hard academic sciences and software development community, consider the differences between a telephone company and an astronomical observatory with a large telescope on a mountain top.

Many people here might be amateur enthusiasts, mixed with a handful of professional academic participants. Any award winning physicists hanging out here would be surprising.

That said, feel free to distinguish yourself by outshining everyone else. It would be a welcome addition.

Re: Physicists demonstrate new way to violate local causality

#42

Post by DesiLurker »

joeberon wrote: post #12

Wow the comments here are weak. Honestly surprised that the physics knowledge is so low here...

well how about writing a series of blog posts to enlighten us lesser mortals. In any case somebody should be doing that.

I am an engineering grad with decade and a half of gap in physics education despite of my constant high level interest/familiarity. I can honestly say I have no idea what bi-local causality is which this article handwaves around in the first para. how can you expect people to debate this when they cant even cut open this basic 'black-box'.

Re: Physicists demonstrate new way to violate local causality

#44

Post by deepnet »

amoruso wrote: post #10

If anyone wants to learn more about Bell's inequality, the simplest (real, no bullshit) explanation I've ever seen is by David Griffiths. You can follow it if you know the basics of calculus: http://www.physics.umd.edu/courses/Phys270/Jenkins/Griffiths...

Interesting to observe the lack of Many Worlds as an interpretation of quantum mechanics in Griffiths excellent explanation.

Re: Physicists demonstrate new way to violate local causality

#45

Post by deciplex »

amoruso wrote: post #10

If anyone wants to learn more about Bell's inequality, the simplest (real, no bullshit) explanation I've ever seen is by David Griffiths. You can follow it if you know the basics of calculus: http://www.physics.umd.edu/courses/Phys270/Jenkins/Griffiths...

The afterword seems kind of weak as it tries to return to the question of what quantum mechanics "means" and then... sort of doesn't really do that. It goes on to describe an "ethereal" influence distinct from causal influence, which is to say an "influence" that doesn't actually do anything at all. That's pretty disappointing.

The simplest explanation of what measurement actually is, in a quantum sense, is that it's the act of entangling your brain with whatever amplitude configuration represents the experiment we're interested in looking at. Basically the amplitude goes from looking like "brain * (result A + result B)" to "brain A * result A + brain B * result B". Brain A at that point can't communicate in any meaningful way with brain B because there isn't any causal relationship between the two anymore, so in a sense the brain has "split" and this is what we call decoherence. But for brain A to suppose that brain B has vanished in a puff of smoke, that is to say to privilege brain A over brain B, needlessly complicates the theory. It is the same as saying that since you can't see a thing anymore, it must not exist, and trying to build an entire physics based around what happens after you close your eyes.

Re: Physicists demonstrate new way to violate local causality

#46

Post by chwind »

Roritharr wrote: post #19
coldtea wrote: post #15

Earlier quoted context omitted.

> Can you recommend an application that would allow me to select for example the words "distant particles can be correlated in ways that are impossible for classical objects" and find out what lead to that discovery? Or what does "Bell inequality" really mean? If not, are there recommended methods of understanding articles better? Venkman: Ray, pretend for a moment that I don't know anything about metallurgy, enginee…

Can you recommend an entry level Physics/QM book?

Definitely _Quantum Mechanics_ by Susskind and Friedman. Only assumes that you are pretty good with probability, and the expositions are nice

Re: Physicists demonstrate new way to violate local causality

#47

Post by ColanR »

coldtea wrote: post #33
ColanR wrote: post #31

Earlier quoted context omitted.

> Weaker than "I don't understand what the paper says, only read a high level layman summary, not sure even what what the experiment was for, but I'm gonna piss on it anyway"? Come on. Parent was saying what it looked like to a layman, and then asking for someone to address that and ask what was actually going on. No need to "piss on [him]".

Well, the parent also wrote "it sounds like they didn't accomplish much" and that the structure of their argument is a strawman -- without qualifications.

The way I read it, the qualifications were implicit through the questions he followed up with; and the whole point of the 'strawman' was that he wanted help to get a better understanding than the obviously wrong impression he got from his 'layman' reading of the article.

Re: Physicists demonstrate new way to violate local causality

#48

Post by gus_massa »

joeberon wrote: post #12

Wow the comments here are weak. Honestly surprised that the physics knowledge is so low here...

Be nice. We all make mistakes in subjects we don't know. I have a few examples in my comment history ...

Try to pick one or two comments that are wrong but not very wrong. Reply to them explaining the error(s). I like to add a Wikipedia link when available.

Ignore the very wrong comments. It's usually impossible to give a coherent reply. You only will get upset.

Also, to encourage a civil discussion try to upvote the grey comments unless they are offensive or extremely wrong.

Re: Physicists demonstrate new way to violate local causality

#49

Post by zeroer »

deciplex wrote: post #45
amoruso wrote: post #10

If anyone wants to learn more about Bell's inequality, the simplest (real, no bullshit) explanation I've ever seen is by David Griffiths. You can follow it if you know the basics of calculus: http://www.physics.umd.edu/courses/Phys270/Jenkins/Griffiths...

The afterword seems kind of weak as it tries to return to the question of what quantum mechanics "means" and then... sort of doesn't really do that. It goes on to describe an "ethereal" influence distinct from causal influence, which is to say an "influence" that doesn't actually do anything at all . That's pretty disappointing. The simplest explanation of what measurement actually is , in a quantum sense, is that it…

I'm not sure if you realize, but you've described the Many-Worlds Interpretation.

Re: Physicists demonstrate new way to violate local causality

#50

Post by zeroer »

semi-extrinsic wrote: post #37
ENGNR wrote: post #36

Earlier quoted context omitted.

I'm in the same boat as you, but started looking a while ago when quantum computers started showing promise. I found: - PBS Spacetime on YouTube is awesome - Check out the double split experiment. It seems simple, but when you think about what getting interference patterns when only sending one particle at a time really means.. - Then when ready, the quantum eraser - Bells inequality is a simple idea that proved the…

If you like the double slit experiment, you'll probably like Feynmann's "motivation" of the path integral in quantum field theory: Suppose you take the double slit (plate with two holes in it), and you start adding more holes. Of course the particle will go through all of them, but with less probability the further they are off-axis. We can also add more than one plate, and the particle will go through all possible c…

That connection between slits in the infinite limit and path integrals is really fascinating. I've read of lot of Feynman, but never that. Where does he talk about it?
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