What sort of an experiment can refute QM or QFTs?

[PeterDonis]

if this didn't produce the correct results, it would just show that the Coulomb potential wasn't the full story.

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

As you noted, there is also e.g. fine structure, but we didn't take its discovery as an argument to reject quantum theory. We just added some higher order terms to account for the discrepancy.

Exactly: these additional terms were due to interactions we already knew were there, just of smaller magnitude so the initial model didn't include them. We added them as measurements became more accurate and we began to see the effects of the higher order terms.

That's very different from having to add a whole new interaction to the model. That might be possible, but it would be very difficult.

 

[bob012345]

The way to do that is to not mention the potentially controversial thing at all. Hinting at it and then saying you can't give more detail because it might get you banned is not avoiding controversy, it's inviting a warning for yourself. Again, please take heed.

I am sorry. I used poor judgement saying that and I apologize.

 

[bob012345]

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

I agree completely with the first sentence but I'm not sure I understand what you mean in the second sentence?

 

[PeterDonis]

I'm not sure I understand what you mean in the second sentence?

Just that if, hypothetically, we imagine that the results of many experiments we have already done were different, then those results might support a different theory. But that sort of hypothetical might not be what the OP intended.

 

[Paul Colby]

The standard Hamiltonian for the electron in the hydrogen atom is not just taken from thin air; it is derived from the standard non-relativistic kinetic energy and the Coulomb potential of the nucleus.

It’s even a little better than that. Equation 14.1.1 in Weinberg vol I is a relativistic Lagrangian bit taken straight from the standard model. The coulomb central potential is the usual one, of course, but the Dirac equation is used for the electron. Adding the em field back in for the Lamb shift is straight forward. Always been impressed by how cleanly this works out.

 

[vanhees71]

Sure, there's not the slightest hint for any violation of the standard-model prediction for the hydrogen atom, although it's among the most accurately measured and theoretically calculated phenomena ever. The reason for this effort is that one always looks for violations of the predictions of the Standard Model and physics beyond it, because (a) one still looks for possible new particles that could make up the "dark matter" in the cosmological standard model needed to explain the velocity curves of stars in most galaxies and also the structure formation in the evolution of the universe in the big-bang model and (b) to overcome the fine-tuning problem.

The theoretical foundation for alternative theories (like SUSY extensions of the Standard Model) is, however, still standard QFT (including SUSY extensions of course). There are very few generic features that are valid for any local relativistic QFT. One is the relation between spin and statistics (half-integer-spin fields have to be quantized as fermions those of integer spin as bosons) and the invariance under the CPT transformation. Both predictions are tested thoroughly as well with no contradictions found (while all the symmetries, P, T, C, CP, etc. are observed to be violated by the weak interaction).

 

[Nullstein]

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Exactly: these additional terms were due to interactions we already knew were there, just of smaller magnitude so the initial model didn't include them. We added them as measurements became more accurate and we began to see the effects of the higher order terms.

That's very different from having to add a whole new interaction to the model. That might be possible, but it would be very difficult.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

 

[MathematicalPhysicist]

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

So do you say the rather disturbing thing:"you cannot falsify Quantum Theory"?

 

[Nullstein]

So do you say the rather disturbing thing:"you cannot falsify Quantum Theory"?

Where did you get that from? I said the opposite in post #26.

 

[bob012345]

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

 

[MathematicalPhysicist]

Where did you get that from? I said the opposite in post #26.

From what you wrote here:" But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort."

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

 

[Nullstein]

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

Luckily, because our best theories remain valid and we don't have to deal with these pseudo-science models. I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

From what you wrote here:" But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort."

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

If you drop a ball and it goes upwards, you have falsified gravity, but not quantum theory. Similarly, you cannot just pick any arbitrary experiment to falsify quantum theory. You must design the experiment in a way so it tests an actual prediction of quantum theory. Quantum theory doesn't predict that balls have to fall down. Gravity does. These "hydrinos" are just not in direct contradictions with quantum theory, so their discovery would not falsify quantum theory. I told you in post #26 what kind of experiments are needed to falsify quantum theory. It's possible to conduct such experiments, so I don't see the problem. QT is not a dogma.

 

[Vanadium 50]

dogma

Puh-lese.

Any successor to quantum theory needs to explain everything QM does. Which means it needs to make very, very similar predictions over the range its been tested.

 

[bob012345]

Luckily, because our best theories remain valid and we don't have to deal with these pseudo-science models. I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

That makes little sense to me. If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science? Are physicists incapable with dealing with a surprise discovery outside the current widely accepted mainstream?

As far as utility goes, hypothetical transitions to lower energy levels of Hydrogen should be an energy source that could benefit humanity if it were true.

 

[bob012345]

Puh-lese.

Any successor to quantum theory needs to explain everything QM does. Which means it needs to make very, very similar predictions over the range its been tested.

Yes but candidate theories might take decades or even centuries to get to that point. For example SED theory or Stephen Wolfram's ideas as depicted in A New Kind of Science.

 

[Nullstein]

That makes little sense to me. If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science? Are physicists incapable with dealing with a surprise discovery outside the current widely accepted mainstream?

As far as utility goes, hypothetical transitions to lower energy levels of Hydrogen should be an energy source that could benefit humanity if it were true.

I really don't want to discuss this specific "theory." I just wanted to point out that it would not be the kind of discovery that would pose a serious threat to quantum theory, because it's not in direct contradiction with it. You'd have to come up with something more drastic.

 

[PeterDonis]

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science?

This is getting off topic. The thread is not about the general philosophy of science but about the specific question in the OP.

 

[PeterDonis]

Yes but candidate theories might take decades or even centuries to get to that point. For example SED theory or Stephen Wolfram's ideas as depicted in A New Kind of Science.

This thread is not about candidate theories to replace QM/QFT but about experiments that could refute QM/QFT. Please stay on topic.

 

[bob012345]

I really don't want to discuss this specific "theory." I just wanted to point out that it would not be the kind of discovery that would pose a serious threat to quantum theory, because it's not in direct contradiction with it. You'd have to come up with something more drastic.

Sticking to experiments, suppose some clever future experiment showed it was possible to simultaneously measure an electron's position and momentum to a greater precision than the HUP? Would not such a result stab at the heart of the core of all QT, the wave nature of matter?

 

[Paul Colby]

Would not such a result stab at the heart of the core of all QT, the wave nature of matter?

Scientific consensus has quite a bit of inertia behind it. Just one experiment and one paper is unlikely to shift it too greatly. First one would have to be convinced the paper's claims are accurate. This alone would take forming a scientific consensus.

 

[bob012345]

Scientific consensus has quite a bit of inertia behind it. Just one experiment and one paper is unlikely to shift it too greatly. First one would have to be convinced the paper's claims are accurate. This alone would take forming a scientific consensus.

Surely but if broadly accepted, would it meet the OP criteria of refuting QT? Of course even if such a thing happened it would not stop the usefulness of the legion of calculational techniques developed in the last 100 years.

 

[Paul Colby]

Surely but if broadly accepted, would it meet the OP criteria of refuting QT?

Well, I’m thinking not but couldn’t say because I don’t know how QM would be changed by this new finding. Somewhere somehow all the things we know today need to be included in any new formulation. This new formulation might well be called QM when the dust clears.

 

[ohwilleke]

What would a falsification of QM look like, if you could do it?

Realistically, you'd be looking at something like superdeterminism in which the universe acts in a manner that is deterministic but observed to be random because it is chaotic in the mathematical sense, with extreme sensitivity of behavior to initial conditions in a way that current experiments are too imprecise to observe but one might imagine some future experiment being capable of observing.

It would be so similar to QM, however, that it would be terribly difficult to find a way to distinguish the two experimentally and there would be little or not applied science benefit to using one over the other. It would suggest strategies to address "the measurement problem", but it isn't at all obvious that equivalent approaches couldn't be developed in the context of orthodox QM.

 

[CoolMint]

How would you falsify a tested quantum computer? What sort of scientific twist would it take?

https://edition.cnn.com/2019/10/23/tech/google-quantum-supremacy-scn/index.html

https://www.nature.com/articles/s41586-019-1666-5

 

[CoolMint]

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

The invisible hand of fate(initial conditions). Or the invisible observer if you like. Either way, we can usually offset the effects of this misfortune by intelligence as it seems to make quite a noticeable difference to what is unfolding. Most times at least.

 

[PeterDonis]

I guess you cannot falsify a dogma which states that the world is not classic.

You don't have to adopt any "dogma" about this. Classical physics was tested by experiment and experiment found it didn't work. That's why we have QM: because classical physics was making wrong predictions about the phenomena experimentalists were seeing at the atomic and subatomic scale in the late 19th and early 20th centuries.

 

[physika]

Yes but candidate theories might take decades or even centuries to get to that point.

maybe not so long, GRW one of the candidates.

.

​

 

[gentzen]

How would you falsify a tested quantum computer? What sort of scientific twist would it take?

Third law of thermodynamics and the scaling of quantum computers

One twist could be the important role of temperature when it comes to increasing the number of qubits.

 

[MathematicalPhysicist]

BTW I read the following in Joseph Polichnski's wiki bio:

In July 2012, Polchinski, with two of his students, James Sully and Ahmed Almheiri, and fellow string theorist Donald Marolf at the University of California, Santa Barbara (UCSB), published a paper[12] whose calculations about black hole radiation suggested that either general relativity's equivalence principle is wrong, or else a key tenet of quantum mechanics is incorrect.

was this problem in his paper resolved eventually?

 

[CoolMint]

Third law of thermodynamics and the scaling of quantum computers

One twist could be the important role of temperature when it comes to increasing the number of qubits.

This, as far as I can see, has been resolved to some extent by Google in their 2018 machine. The first computer in the world was as big as a room and is a million times less powerful than a low budget smartphone of today, so time will bring better and more practical solutions.

People take issue with QT because they cannot live without knowing. Without the cushion of the familiar classicality and objects in time and space.
I have no issue with everything being mostly the result of electromagnetism. One day, gravity too will be described in quantum terms - the remaining question will be - how did we come to the conclusion that we knew what we had assumed? If anything, the history of physics and science show that every knowledge is provisional, pending falsification.

 

[PeterDonis]

was this problem in his paper resolved eventually?

The whole area of research of which that paper was an example, basically how to reconcile quantum field theory with GR (which is not limited to the case of black holes although black holes do highlight a number of key issues), is still open and unresolved.

 

[physika]

BTW I read the following in Joseph Polichnski's wiki bio:

was this problem in his paper resolved eventually?

now summed up in the hairy vs not hairy dispute.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.111301

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.055101

 

[gentzen]

This, as far as I can see, has been resolved to some extent by Google in their 2018 machine.

That was a link to a paper from 2022, so if their concern would have already been resolved in 2018, then the paper would be invalid to some extent. The paper references Google's results, and I see the following quotes from that paper against that background:

We argue that, in order to go beyond NISQ devices, substantial efforts are needed to improve not only the fidelity of single gates, but also the quality of initialization of multi-qubit registers. Thus, with this work, our aim is to help improving the design of quantum protocols and devices that properly takes into account fundamental thermodynamic constraints, hitherto neglected.

Accordingly, in order to move beyond NISQ devices, we need to prepare pure states with increasing fidelity by properly taking into account also the needed resources, at least at the energetic level. In doing this, quantum state initialization could need to be improved at a faster rate than the one at which the size of quantum computers increases.

Now I am unsure about the level you want to discuss such a paper, and also unsure about the allowed level of discussion in a B(eginner) level thread. Anyway, here is my opinion about the objections against scalable quantum computing from that paper:

I thought about similar "temperature based objections" against scalable quantum computing in the past, but the open question for my approach was whether quantum error correction could allow to limit the relevant size of the states to be considered. This paper might circumvent this question by focusing on the initial state instead. But maybe the question is still there, "conservation of difficulty", I currently simply don't know.

 

[Fra]

I assume most people when they refer to Quantum Theory, they sort of referring to QFT.

So my question boils down to, what sort of an experiment could potentially refute QFTs (its plural because there are QF theories)?

When pondering about this, I think the falsification paradigm is a bit blunt and uselss. As long as one considers QFT as effective theories, I don't see an obvious way how to falsify it as you can probably always tweak the parameters, enlarge the state spaces etc. But if one tries to ask, how the effective theories FORM, one may be required to step outside the QFT paradigms. In this sense, I doubt there will be a single experiment that refutes QFT, I think it will be if an alternative paradigm demonstrates it's superioirty in solving some open questions. Superior maybe in the sense or computation complexity, compact representation etc. Ie. I think it's not sufficient for a theory to be consistent, it must also be solvable or computable by it's host agent - otherwise it is useless. It's in these sense I think the current paradigms may need rethinking. Ie. it is not enough that something is solvable in principle, if it is not solvable by the resources at hand, then what is it's value, and rational from a naturalness perspective?

/Fredrik

 

[bob012345]

I'm not sure if this would qualify but in the spirit of this paper and talk;

https://www.researchgate.net/publication/224775736_There_are_no_particles_there_are_only_fields
https://www.preposterousuniverse.com/blog/2020/05/19/the-biggest-ideas-in-the-universe-9-fields/
https://www.symmetrymagazine.org/article/july-2013/real-talk-everything-is-made-of-fields

If an experiment could show there are particles such as the electron, distinguishing it from fields, would that violate the modern notion of QFT?