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).
There might be a small, very hard to detect optical interference shift if the experiment were re-run with a coherent laser beam.
The paper itself is here:
It's paywalled and unfortunately I have not been able to find a preprint on arxiv.org.
That comment is short, succinct and understandable, it's the best summary of the physics involved that I've heard in so few words.
It seems to me that we don't put sufficient emphasis into considering potentials. Viewing things from the aspect of potentials I reckon changes one's perspective, and I think the Aharonov-Bohm effect is a case in point, without doing so we easily come aground.
However, the Aharonov-Bohm effect still perplexes me more than I'd like - in QM, why exactly does potential have observable effects? Why is it that a phase shift occurs in the wave function of a charged particle in the near vicinity of a solenoid even though both magnetic and electric fields are negligible? (I'm either not convinced by explanations that I've heard to date or thst I don't fully understand them.)
Whilst my understanding of the Aharonov-Bohm effect is deficient in this regard, it nevertheless seems to me that if the effect can also be detected in a gravitational field context then we've likely found a profound and deeply relevant connection between EM fields/relatively and gravity. If verified, then we'd have to consider it a breakthrough in our understanding of what up until now has been an intractable problem.
The key point is that we've now experimental evidence for such a connection and that's really good news.
I'm not sure I'd say it's a breakthrough since theorists have expected it all along. And current treatments of this all have a key limitation, that they are using non-relativistic QM. Which in practice works fine since all the experiments we can currently do in this area are well within the non-relativistic domain.
A real breakthrough would be a relativistic quantum theory that included gravity as well as the other interactions. But that's probably still some way off.
Yeah, sometimes one has to be optimistic. I'm aware of the limitations of using non-relativistic QM but it seemed to me that this experimental connection, if confirmed, would encourage or even force relativistic work to center stage.
Essentially, both theoretical and experimental practitioners could now say 'we've now a concrete stating point'. On reflection, I wouldn't expect a full GR explanation to come easy. Still, it's a start.
The simple answer is that it's right there in the Hamiltonian, and the Hamiltonian is the central operator in QM, the one that determines time evolution. The fact that the EM potential appears there has been known almost as long as QM itself. Much of the recent QM experimentation in gravitational fields has been making use of recent technological advances to verify, what theorists have expected all along, that the gravitational potential acts just like the EM potential in the Hamiltonian.
It's a while since I last looked at Aharonov and Bohm's '59 paper but if I recall your point about the Hamiltonian is covered there. My understanding is that in this paper the key difference from the earlier work to which you also refer is that their new solution to the Hamiltonian now involves a phase factor.
The point I should have made was that I wasn't thinking so much about the mathematical explanation of the Aharonov-Bohm effect but in more general terms where perhaps this new experimental work may reinvigorate interest in the subject and in related areas.
Whilst QFT provides us with an exquisitely accurate mathematical account for the purposes of calculation, it says little about the underlying physics per se. Thus, it seems to me that we stil have a limited understanding about the nature of say virtual particles, ZPE, etc. and essentially no understanding of why the electric, magnetic and fine structure constants and others are the values they are.
Research into the Aharonov-Bohm effect, could eventually lead to a deeper more fundamental understanding of the subject although, given past history, I fully accept that coming up with a major breakthrough in the near future is probably unlikely. (It's even more unlikely that we'll resolve the constants problem anytime soon, if at all.)
It seems to me that the most significant aspect of this work is that we now have more than just a theoretical framework that connects EM and gravity/the gravitational field at a QM level (or seemgly so). Tenuous it may be but it seems like a good start.
For my part, I still worry about why, say, the electric and magnetic constants have the value they do or why our understanding of ZPE is seemingly at odds with reality given the ludicrous value of the calculated zero-point radiation of the vacuum. But then, this is more about philosophy than it is about physics.
Re SQUIDs, likewise, I could amuse myself for ages if I had several to play with.
Importantly, it's "famed" and "eerie."
> 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.
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.
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.
Right, it seems that for many the 'potential' worldview is hard to grasp (it was for me too until it drawned on me that it's important).
I blame this on poor training and poor textbooks, they don't emphasize the importance of potentials. Also, we seem to grow up with a 'fields' perspective, electric fields and so on.
Maxwell was on the 'right' path with his original formulation of his equations where potentials were involved. However, when Heaviside reformulated them to the 'vector' view we quickly lost the 'potential' one.
No doubt, Heaviside's formulation is incredibly useful in electrical engineering and eleconics and as you'd know that's how they usually appear in textbooks. Trouble is, outside advanced physics texts the 'potential' view is usually omitted. Educators really need to fix this.
Another problem is that the description of a potential is not up to scratch. All too often we seem to be stuck with highschool physics descriptions - those that involve pith balls. The concept that we never measure absolute energy, but only differences often gets lost when describing potentials.
You'd reckon that after Feynman's well documented whingeing about the fact he wasn't taught about potentials early enough that you'd think by now educators would have had sufficient time to have rewritten their notes but apparently they've not.
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...
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.
what is free fall in a reference frame is a particle subject to a force in another reference frame.
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.
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.
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.
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.
In my view, the latter is by far the most difficult and failing to come up with a common objective or view is likely to either scuttle the project or render it ineffective or inefficient.
Let me give you a real world example: Linux. We've so many distros that it's hard for anyone of them to get real traction. As we've seen for decades, Linux has never managed to take on Windows on the desktop for the reason that there are so many disparate views about how tackle the problem. Both businesses and ordinary users want certainty not constant variation.
We see the same problem in other areas of the net, for instance copyright reform. The only way to tackle that is on a worldwide basis - as the forces against it are aldo already very well organized on a worldwide basis and have been so for some 140 years (since the original Berne Convention).
I've often thought that we need a worldwide union of computer users to tackle these issues and take on Big Tech, etc. but how does one start something as big and significant as this let alone hold it altogether for any length of time?
I wish I knew.
quantum physics: the biggest waste of time since philosophy
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
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.
Then he continued and explained how a junction transistor worked with the same equations!
No QM required.
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.
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.
LEDs weren't discussed that day.
Oh, and Casimir cavities.
Sure. After all, natural sciences from physics to biology used to be called natural philosophy until not so long ago.
> 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.