[HN Gopher] Quantum particles feel the influence of gravitationa...
___________________________________________________________________
Quantum particles feel the influence of gravitational fields they
never touch
Author : pseudolus
Score : 70 points
Date : 2022-01-14 11:00 UTC (12 hours ago)
(HTM) web link (www.sciencenews.org)
(TXT) w3m dump (www.sciencenews.org)
| bubblecheck wrote:
| (Per the article): Is it correct to describe superposition as the
| probability of, e.g., an electron being in one of two places? In
| such an example, is it instead correct to say that superposition
| is a probability distribution of infinitely many possible
| locations?
| monocasa wrote:
| It depends. In the general case a superposition is a
| probability field with infinitely many options once the
| waveform collapses, but the specifics of the experiment might
| discretize that practically into two options.
| [deleted]
| sandworm101 wrote:
| 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.
| notfed wrote:
| Quantum mechanics news hasn't been giving us anything new for
| decades. Every modern article is about a new speculation, or at
| best an or experiment that reconfirms what we already knew.
| Yet, articles will never cease to use click-bait to make you
| think a revolution has occurred.
| amelius wrote:
| There was an article about China reaching quantum supremacy
| some time ago, so I suppose we achieved _something_.
| sandworm101 wrote:
| The closer you can get the words "quantum" and "gravity"
| together in the title the better.
| changoplatanero wrote:
| 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.
| criddell wrote:
| 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.
| pdonis wrote:
| 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.
| kenjackson wrote:
| Is that the common way you'd express that they were
| measured in free fall -- that the effects were "filtered"
| out? That seems like an odd way of saying it, but I'm not a
| physicist.
| pdonis wrote:
| I don't think it's a very good way of expressing that the
| objects were in free fall, no. Nor, as far as I can tell,
| does the actual paper (as opposed to the pop science
| article) use such an expression.
| Arwill wrote:
| 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.
| pdonis wrote:
| _> 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.
| Arwill wrote:
| >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...
| pdonis wrote:
| _> they did measure a difference_
|
| They measured a phase shift in the wave function, as I
| said. They did not measure any direct difference in
| "gravitational effect" on the particles, as for example a
| difference in bending of their trajectories due to the
| source mass would be.
|
| _> the expression "not touching the field" makes
| perfect sense to me_
|
| The problem with it, as several commenters have pointed
| out, is that you can't shield anything from gravity. The
| "not touching the field" comes from electromagnetism,
| where you _can_ shield things from the field. So the
| "not touching the field" interpretation, while it works
| for EM, does not work for gravity.
| martopix wrote:
| > There is no "gravitational force" in free fall, and the
| particles were in free fall.
|
| what is free fall in a reference frame is a particle
| subject to a force in another reference frame.
| pdonis wrote:
| No, it isn't. Free fall is invariant: attach an
| accelerometer to the object and it reads zero. That is
| true regardless of your choice of reference frame.
| PicassoCTs wrote:
| 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.
| pdonis wrote:
| While this is of course possible in theory, it's not at all
| what was being done in this experiment.
| wilbdhm wrote:
| wongarsu wrote:
| 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.
| pdonis wrote:
| 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.
| mikewarot wrote:
| You're right, most descriptions of Aharonov-Bohm fail to
| mention _Electromagnetic Potential_ , and just describe it as
| quantum woo. I'd love to have an actual quantum detector,
| like a SQUID, to do some physics experiments with.
| Koshkin wrote:
| > _description_
|
| Importantly, it's "famed" and "eerie."
| hilbert42 wrote:
| _" The two theories that underlie this experiment, general
| relativity and quantum mechanics, don't work well together."_
|
| The Aharonov-Bohm effect alone is perplexing enough and there
| isn't full unanimity about the theory that underpins it. That
| we're seeing a similar effect with gravity is truly exiting as I
| reckon it will attract a great deal more research in this area.
|
| It seems to me that Aharonov-Bohm effect now has a gravitational
| parallel tells us that we're honing in closer and closer to
| having a quantum understanding of gravity.
|
| Excellent stuff.
| ianai wrote:
| Sounds more like a demonstration of an ability to detect the
| influence of gravitational fields at scales previously
| unavailable. Specifically, in testing something called the
| "Aharonov-Bohm influence/[effect]" previously demonstrated within
| EM fields and now for gravity.
|
| Quote: """
|
| The study not only reveals a famed physics effect in a new
| context, but also showcases the potential to study subtle effects
| in gravitational systems. For example, researchers aim to use
| this type of technique to better measure Newton's gravitational
| constant, G, which reveals the strength of gravity, and is
| currently known less precisely than other fundamental constants
| of nature (SN: 8/29/18).
|
| """
| mikewarot wrote:
| The wavelength of an atom (DeBroglie Wavelength) is much lower
| than that of a photon of visible light, so it follows that
| anything that makes the path of one beam even slightly longer,
| such as putting a mass near it, would be far more detectable in
| this manner.
|
| There might be a small, very hard to detect optical
| interference shift if the experiment were re-run with a
| coherent laser beam.
| squeaky-clean wrote:
| 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.
| krastanov wrote:
| 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).
| cashsterling wrote:
| i think a possible startup idea would be to start a "Github for
| science" (replace "science" with any academic or interest area
| really). Encourage folks to post their papers in latex or
| markdown. Post their data, code, mechanical and electrical
| drawings, videos and pictures of their experimental setup,
| videos explaining their research, videos performing the
| experiment?, and so on. Allow others to comment on research
| with questions, concerns, suggestions for enhancement, or link
| it to their own supporting work, etc. Allow other researchers
| to fork people's research (but all forks link back to the
| original to give full attribution). The core focus is open up
| access to academic papers and research, foster better
| communication between people, and set a higher bar for
| communication of research.
|
| Going the non-profit route: I think it would be cool for the
| site to be federated/distributed so universities & countries
| could host replicated nodes. It would be best if somehow the
| software system development and hosting costs could be
| underwritten by governments and universities.
|
| Going the for-profit route: The site could have an inexpensive
| PRO account to help support the site and software development.
| The site could be add supported, but zero tracker, with adds
| that would be small and content-based purely on the content of
| the paper topic.
|
| Add Examples: Reading an article on Julia numerical
| programming... maybe show an add for the upcoming JuliaCon or
| Julia Computing
|
| Reading a metallurgy analysis paper... maybe show a small add
| for an x-ray fluorescent system for metal composition analysis
| or advertise an upcoming metallurgy conference
|
| ... the idea being that these adds are (1) not targeted at
| users, just targeted at content, (2)small, dismiss-able, and
| not annoying (3) hopefully actually useful and interesting to
| the reader.
|
| The site could also sell "advanced API access" to interested
| parties for knowledge management/search on fast trending
| research and topical areas, research community graph analysis
| (maybe for recruiting?)... kind of the LinkedIn layer of the
| site.
| ambrozk wrote:
| Just use sci-hub. It always works, and it's very easy. There's
| no good reason to give the journal your money to read an
| article they had no hand in writing or funding.
| diontron wrote:
| 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
| kgwgk wrote:
| > quantum physics: the biggest waste of time since philosophy
|
| Sure. After all, natural sciences from physics to biology used
| to be called natural philosophy until not so long ago.
| jakeinspace wrote:
| 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, and
| quantum mechanics is our attempt to predict outcomes based on
| an incomplete understanding? That is a defensible position, but
| it still wouldn't make sense to call quantum physics a waste of
| time.
| diontron wrote:
| Quantum physics is worse than a waste of time. It actually
| impedes real progress.
|
| http://www7b.biglobe.ne.jp/~kcy05t/index.html
|
| Enjoy.
| kingcharles wrote:
| OK, Mr Troll. That site is like I had a seizure while
| playing with Adobe Dreamweaver.
| gpderetta wrote:
| I was expecting Time Cube, but close enough I guess.
| JaimeThompson wrote:
| What about the use of quantum physics in things like
| semiconductors?
| diontron wrote:
| semiconductors don't "use" quantum physics, quantum physics
| just tries to explain how they work. semiconductors still
| exist without requiring quantum physicists to come in and try
| and steal credit for something they had no influence on
| whatsoever.
| evanb wrote:
| Not for nothing but Shockley, Bardeen, and Brattain were
| physicists awarded a Nobel "for their researches on
| semiconductors and their discovery of the transistor
| effect". Bardeen also won a separate Nobel for a theory of
| superconductivity. Claiming they're not quantum physicists
| or had no influence on semiconductors is misinformed.
| klyrs wrote:
| Now do Josephson Junctions.
| https://en.wikipedia.org/wiki/Josephson_voltage_standard
| ben_w wrote:
| Indeed, or superfluids, Fermi-Dirac and Bose-Einstein
| condensates, quantum computers, lasers, quantum dot
| displays, quantum key distribution, MRI scanners, that
| trick with 3 polarising filters letting though more light
| than just 2, antimatter, and electron microscopes.
|
| Oh, and Casimir cavities.
| pmontra wrote:
| They used to but manufacturers are starting to have to deal
| with quantum effects lately
| https://semiengineering.com/quantum-effects-at-7-5nm/
| danbruc wrote:
| Nothing in the universe >>uses<< quantum physics. Or
| classical physics. Or any physics. Or any science. Or
| anything made by man. Or aliens. All a waste of time and
| resources.
| dekhn wrote:
| This is sort of a profoundly different way of looking at
| it. The creation of the first semiconductors was closely
| tied to the development of quantum theory around electrons
| in metal. Bell labs hired up Shockley, Bardeen and a bunch
| of other solid state physicists (when it started to become
| obvious that the US needed to build computing devices that
| were faster and more rugged than vacuum tubes) and it was
| their knowledge of quantum physics that enabled them to
| solve key problems in the development of the transistor.
|
| QM is still the best theory for semiconductors and a lot of
| semiconductor improvement happens by applying quantum
| physics.
|
| The important part to recognize is that this is a part of
| QM that doesn't involve entanglement or wave function
| collapse, but definitely relies heavily on quantum
| tunnelling. All of this is well documented by the primary
| literature in the field.
| mikewarot wrote:
| It may be that is how it started, but I'll never forget
| the day my Advanced Chemistry teacher at Rose-Hulman used
| standard chemistry (I think it was the Nerst equation, 40
| years ago!) to explain how a diode works.
|
| Then he continued and explained how a junction transistor
| worked with the same equations!
|
| No QM required.
| dekhn wrote:
| The nernst equation is
| https://en.wikipedia.org/wiki/Nernst_equation (redox).
| THere's also https://en.wikipedia.org/wiki/Nernst%E2%80%9
| 3Planck_equation which also isn't exactly for diode
| modelling.
|
| I'm sure you can find classical equations that model some
| aspects of p-n junctions but you're ultimately going to
| see that p-n junction physics is literally quantum
| physics of tunneling electrons in atomic solids.
| mikewarot wrote:
| It's not tunneling, it's conduction. There are liquid
| electrolytic rectifiers, they suck, but they exist.
| dekhn wrote:
| Oh, I see what you're saying now. Your teacher showed you
| the equations explaining a classical (pre-semiconductor)
| diode, then showed those equations predict some aspects
| of semiconductor diodes.
|
| Yeah, that doesn't mean that diodes don't work in a
| fundamentally quantum way. There are a number of details
| about diodes (for example, the emitted frequency of light
| in an LED) that are very specifically due to quantum
| energy transitions of electrons in outer shells. It
| doesn't get any more quantum physics than that.
| baja_blast wrote:
| How is explaining/figuring out how quantum physics effects
| semiconductors "stealing credit"? Learning about how
| quantum tunneling effects impact super small transistors is
| extremely useful since chip designers can use this info to
| design chips that mitigate this effect as we scale down.
|
| Also in the material sciences metamaterials have special
| properties precisely because of how the molecular structure
| manipulates quantum forces.
| https://www.nature.com/articles/s41467-019-09939-8
| Chris2048 wrote:
| It says:
|
| > subatomic particles can feel the influence of this warping
| even if they aren't subject to gravitational forces
|
| So I guess they are talking about particles without mass.
| quantum_state wrote:
| Completely misleading and eye ball gripping "article' ...
| dang wrote:
| Quite possibly, but a comment like this is only helpful if it
| explains how the article is misleading--i.e. if it provides
| more correct information on the topic. Otherwise it's just
| another low-quality dismissal, which we're trying to avoid
| here.
|
| https://news.ycombinator.com/newsguidelines.html
___________________________________________________________________
(page generated 2022-01-14 23:02 UTC)