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Quantum particles feel the influence of gravitational fields they never touch

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Re: Quantum particles feel the influence of gravitational fields they never touch

#21

Post by pdonis »

changoplatanero wrote: post #3

I'm not sure how it's possible to "never touch" a gravitational field given that they extend throughout the universe and are impossible to be shielded.

As is unfortunately common in pop science writeups, the article gives a garbled description of what the Aharonov-Bohm effect actually is. The key point is not that "the field never touches the particles". The key point is that the potential, rather than the field, has an observable effect. In classical gauge theories, the potential itself is not considered to be observable; only the field (the gradient of the potential) is. However, in QM, the potential itself can have observable effects. That's what's going on here, but with the gravitational potential instead of the EM potential (as in the ordinary Aharonov-Bohm effect).

The paper itself is here:

https://www.science.org/doi/10.1126/science.abl7152

It's paywalled and unfortunately I have not been able to find a preprint on arxiv.org.

Re: Quantum particles feel the influence of gravitational fields they never touch

#22

Post by pdonis »

criddell wrote: post #8
changoplatanero wrote: post #3

I'm not sure how it's possible to "never touch" a gravitational field given that they extend throughout the universe and are impossible to be shielded.

They touch on that in the article: > Notably, the particles weren’t in a gravitational field–free zone. Instead, the experiment was designed so that the researchers could filter out the effects of gravitational forces, laying bare the eerie Aharonov-Bohm influence. I'm no physicist, but I think they calculated the expected influence and compared that with a measurement.

The "filter out the effects of gravitational forces" means that the measured particles were in free fall; in free fall there is no gravitational force.

Re: Quantum particles feel the influence of gravitational fields they never touch

#23

Post by pdonis »

Arwill wrote: post #20
changoplatanero wrote: post #3

I'm not sure how it's possible to "never touch" a gravitational field given that they extend throughout the universe and are impossible to be shielded.

They measured a bigger gravitational effect on the particle, because the superpositional pair of the particle flew closer to a mass than the actually measured particle. Regarding the "never touch", gravity decreases with distance squared, so it diminishes quickly with distance. There is a big difference in being near the mass, as opposed to feeling the dimished effect of it from far.

> They measured a bigger gravitational effect on the particle

No, they didn't. They measured a phase shift in the particle's wave function. There is no "gravitational force" in free fall, and the particles were in free fall.

> gravity decreases with distance squared

The Newtonian gravitational force does, but the Newtonian gravitational force is irrelevant for an experiment conducted in free fall, as this one was. The gravitational potential is the key thing being measured, and it's not the potential due to the Earth, it's the potential due to a 1-kg "source mass".

> There is a big difference in being near the mass, as opposed to feeling the dimished effect of it from far.

The particles were near the 1-kg source mass.

Re: Quantum particles feel the influence of gravitational fields they never touch

#24

Post by pdonis »

PicassoCTs wrote: post #17
changoplatanero wrote: post #3

I'm not sure how it's possible to "never touch" a gravitational field given that they extend throughout the universe and are impossible to be shielded.

One, in theory could shield of them, by having the same field apply from the opposing direction and distance. So if one could create such a "mirror" copy of all attractors - one would have a L1 Lagrange point. The forces still interact, but chancel each other out.

While this is of course possible in theory, it's not at all what was being done in this experiment.

Re: Quantum particles feel the influence of gravitational fields they never touch

#25

Post by squeaky-clean »

I know this is a trope that comes up in half of the posts involving a journal article, but scientific journal pricing is so confusing to me.

I can pay $30 for digital access to a 4 page article (it says Vol 375 pg 226-229). Or I can pay $15 and get the entire issue of Vol 375 in print? Or I can pay $80/yr to join AAAS and get "50 issues of Science", but which issues? I assume they mean the upcoming year of issues, but I still want to read issue 375...

I consider buying or joining every once in a while when a cool article like this links back to a paper I can't find on Arxiv. But then I remember how expensive individual articles are and how confusing it is to sign up.

Re: Quantum particles feel the influence of gravitational fields they never touch

#26

Post by wongarsu »

changoplatanero wrote: post #3

I'm not sure how it's possible to "never touch" a gravitational field given that they extend throughout the universe and are impossible to be shielded.

Changes in the gravitational field are only propagated at the speed of light, so in principle you could say something "never touched" a gravitational field if it just hasn't been reached by it yet.

Re: Quantum particles feel the influence of gravitational fields they never touch

#27

Post by Arwill »

pdonis wrote: post #23
Arwill wrote: post #20

Earlier quoted context omitted.

They measured a bigger gravitational effect on the particle, because the superpositional pair of the particle flew closer to a mass than the actually measured particle. Regarding the "never touch", gravity decreases with distance squared, so it diminishes quickly with distance. There is a big difference in being near the mass, as opposed to feeling the dimished effect of it from far.

> They measured a bigger gravitational effect on the particle No, they didn't. They measured a phase shift in the particle's wave function. There is no "gravitational force" in free fall, and the particles were in free fall. > gravity decreases with distance squared The Newtonian gravitational force does, but the Newtonian gravitational force is irrelevant for an experiment conducted in free fall, as this one was. Th…

>Each of those two sets of atoms were split into superpositions, with one path traveling closer to the mass than the other, separated by about 25 centimeters

One path of the particle in superposition was closer to the 1.25Kg mass than the other path, and they did measure a difference when doing that.

I don't know if you are trying to be pedantic, or just want to contradict. I know what you are saying, but the the expression "not touching the field" makes perfect sense to me. Try plotting the 25cm distance difference for the 1.25Kg mass, and see if it makes a difference or not...

Re: Quantum particles feel the influence of gravitational fields they never touch

#28

Post by krastanov »

squeaky-clean wrote: post #25

I know this is a trope that comes up in half of the posts involving a journal article, but scientific journal pricing is so confusing to me. I can pay $30 for digital access to a 4 page article (it says Vol 375 pg 226-229). Or I can pay $15 and get the entire issue of Vol 375 in print? Or I can pay $80/yr to join AAAS and get "50 issues of Science", but which issues? I assume they mean the upcoming year of issues, bu…

Your confusion is warranted, the system has twisted incentives. I am a scientist working at a rich university. I still mostly use scihub unless the article is on arxiv, even for articles which have my name in the byline. All this to say, I consider pirating these papers the moral highground and you should not feel bad doing it. Thankfully, I have the job security and funding to demand my work be open access (a whole other can of worms).

Re: Quantum particles feel the influence of gravitational fields they never touch

#29

Post by sandworm101 »

I don't see the new. All this tells me is that entangled particles react to things that impact some but not all of their various superpositions/entanglements. Sounds like basic double-slit stuff to me. The particle that goes through the slit A reacts to its partners going through slit B. The particle that passed through gravity field A reacted to its partners going through field B.

Re: Quantum particles feel the influence of gravitational fields they never touch

#30

Post by diontron »

jakeinspace wrote: post #12
diontron wrote: post #4

article goes on to state that gravitational pull effects surrounding objects without touching them, you know, like how we already know every fucking planet works? quantum physics: the biggest waste of time since philosophy

You're about a hundred years late to be making this stand. I've never actually seen anyone claim that quantum physics in general is hooey. What do you even mean by that? That in fact, all of modern physics observations, as well as cosmology, materials science, etc, can actually be explained by classical physics? Or do you mean that you think there is some underlying classical/deterministic process which drives nature…

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