Insights Quantum Entanglement is a Kinematic Fact, not a Dynamical Effect

[Greg Bernhardt]

TL;DR Summary

In the 1990s “second quantum revolution,” physicists began treating quantum mechanics as a principle theory, much like Einstein reframed relativity. Building on Rovelli’s challenge, information theorists such as Hardy showed that quantum features like superposition and entanglement follow necessarily from the observer-independence of Planck’s constant...

Insights auto threads is broken atm, so I'm manually creating these for new Insight articles.

Towards the end of the first lecture for the Qiskit Global Summer School 2025, Foundations of Quantum Mechanics, Olivia Lanes (Global Lead, Content and Education IBM) stated...

Source: https://www.physicsforums.com/insig...t-is-a-kinematic-fact-not-a-dynamical-effect/

by @RUTA

 

[Hornbein]

Well I'll be danged. One wonders why this result is so little known.

I'm too cheap to buy the book, which I wouldn't understand anyway.

 

[elias001]

@Greg Bernhardt Wait, my naive understanding is that if there are two locations say A and B with some distance $x$ apart. If we have a particle at location A and another one at location B, then the two particles can be entangled. I assume there needs to be some sort of scientific equipments located at both locations A, B.

So what happens if I just have location A, and I have a particle name Bob, and I want to entangled some other particle at another location of whatever distance $y$ from A. Say we know at distance $y$ from A, there is some sort of stellar body. But but we can't exactly reach it in a human life span, even if we have faster than light travel. That means we can't drag scientific equipment $y$ distance from location A.

However, from popular media, for quantum radars, dragging any scientific equipment $y$ distance from location A is not necessary.

 

[dextercioby]

@Greg Bernhardt Wait, my naive understanding is that if there are two locations say A and B with some distance $x$ apart. If we have a particle [...]

Were you trying a comment on the article or a ask the author a question? Then quote @RUTA (the author), not Greg (admin & site owner), who only made it possible that the text written in the site's "Insights" section be quoted/advertised here in the discussion board.

 

[elias001]

@dextercioby I am asking or am talking to @Greg Bernhardt in my reply. I asked as a lay person. My impression is Greg Bernhardt is an all around pretty knowledgeable chap.

 

[Greg Bernhardt]

@dextercioby I am asking or am talking to @Greg Bernhardt in my reply. I asked as a lay person. My impression is Greg Bernhardt is an all around pretty knowledgeable chap.

Not in physics, ironically

 

[PeterDonis]

I am asking or am talking to @Greg Bernhardt in my reply.

You might not understand that @Greg Bernhardt did not write the Insights article that is referenced, and is not the right person to ask questions about it. The right person is the person who did write it, i.e,. @RUTA.

 

[RUTA]

Well I'll be danged. One wonders why this result is so little known.

I'm too cheap to buy the book, which I wouldn't understand anyway.

It's a relatively new twist on the quantum reconstruction program. The book is the culmination of about 4 years of development (papers, blogs, and conference presentations) and it was published just last year.

I made a 5-part YouTube video series totally less than an hour if you want an overview. Here is episode 1:

 

[Grinkle]

@RUTA SR threads here often have a shared plotline, which I'll illustrate by example below -

Q: Why do clocks move differently in different inertial frames?
A: It follows directly from SR, which is based on the empirical observation that c is the same in all inertial frames.
Q: Why is that?
A: Physics doesn't say - its not the only way a universe can be self-consistent, but its how ours is. A constant speed of light must be experimentally determined.

Why aren't QM interpretation threads following a similar plotline, in your view? While I find the perspective you present very appealing, I'm wondering why it wouldn't be a thematic answer to the myriad interpretation threads here.

 

[RUTA]

@RUTA SR threads here often have a shared plotline, which I'll illustrate by example below -

Q: Why do clocks move differently in different inertial frames?
A: It follows directly from SR, which is based on the empirical observation that c is the same in all inertial frames.
Q: Why is that?
A: Physics doesn't say - its not the only way a universe can be self-consistent, but its how ours is. A constant speed of light must be experimentally determined.

Why aren't QM interpretation threads following a similar plotline, in your view? While I find the perspective you present very appealing, I'm wondering why it wouldn't be a thematic answer to the myriad interpretation threads here.

Let me add something to that plot line before answering your question. The light postulate is not acceptable as an explanans for most people, indeed Lorentz complained "that Einstein simply postulates what we have deduced [the light postulate], with some difficulty and not altogether satisfactorily, from the fundamental equations of the electromagnetic field" (quote below). The reason most people accept the derivation of the Lorentz transformations from the light postulate as explanatory is that the light postulate follows from the relativity principle and Maxwell's equations (the last sentence in this Lorentz quote):

It will be clear by what has been said that the impressions received by the two observers A0 and A would be alike in all respects. It would be impossible to decide which of them moves or stands still with respect to the ether, and there would be no reason for preferring the times and lengths measured by the one to those determined by the other, nor for saying that either of them is in possession of the ``true'' times or the ``true'' lengths. This is a point which Einstein has laid particular stress on, in a theory in which he starts from what he calls the principle of relativity, ... .

I cannot speak here of the many highly interesting applications which Einstein has made of this principle. His results concerning electromagnetic and optical phenomena agree in the main with those which we have obtained in the preceding pages, the chief difference being that Einstein simply postulates what we have deduced, with some difficulty and not altogether satisfactorily, from the fundamental equations of the electromagnetic field. By doing so, he may certainly take credit for making us see in the negative result of experiments like those of Michelson, Rayleigh and Brace, not a fortuitous compensation of opposing effects, but the manifestation of a general and fundamental principle.

So the ultimate explanans is the relativity principle, which most physicists seem to find compelling (we explain why at length in Chapter 1 of our book "Einstein's Entanglement"). That's what I present in this Insight. Now to your question.

The principle account of QM given in this Insight whereby QM parallels special relativity (SR) is a very new (3 years-old) completion of a relatively new reconstruction of QM via information theoretic principles (Masanes & Mueller, 2011). I'm still working on getting the word out in papers, blogs like this one, The Conversation, OUP, and Science X, and at conferences in Helsinki, Bristol, Vienna, Los Angeles, Vaxjo, Trieste, and Rome. Many of my colleagues in foundations of QM find it appealing and surprising (e.g., see book blurbs by Adlam and Brukner), but it will take some time before it is accepted like SR because most in quantum foundations are still looking for a constructive account of QM whereby entanglement is a dynamical effect. Einstein's principle reconstruction of the Lorentz transformations was likewise ignored for many years because everyone wanted a constructive account a la the luminferous aether (some are still looking today!). Even Einstein felt SR needed a constructive counterpart. Here is what he wrote to Sommerfeld in 1908:

It seems to me too that a physical theory can be satisfactory only when it builds up its structures from elementary foundations. The theory of relativity is not more conclusively and absolutely satisfactory than, for example, classical thermodynamics was before Boltzmann had interpreted entropy as probability. If the Michelson-Morley experiment had not put us in the worst predicament, no one would have perceived the relativity theory as a (half) salvation. Besides, I believe that we are still far from satisfactory elementary foundations for electrical and mechanical processes. I have come to this pessimistic view mainly as a result of endless, vain efforts to interpret the second universal constant in Planck's radiation law in an intuitive way.

That last sentence is ironic because we now see that QM and SR are principle explanations based on the same relativity principle and after 100 and 120 years, respectively, neither has a consensus constructive counterpart. But since this is such a new discovery and the dynamical-constructive-causal bias runs very deep, I imagine it will take some years of promotion before it is widely accepted as a viable alternative to Bohmian mechanics, retrocausality, superdeterminism, QBism, GRW, and Many Worlds :-)

 

[Grinkle]

Thanks for taking the time to give that response, much appreciated. It has got to be fatiguing continually articulating things at a "B" level, I don't take those efforts by everyone here for granted.

a relatively new reconstruction of QM via information theoretic principles

If its possible to explain conceptually, what is new about the reconstruction that would make it more compelling vs prior constructions? Is it the concept that h-bar stays constant for all inertial frames be taken as an axiom?

What objections, if any, are you encountering?

 

[RUTA]

Thanks for taking the time to give that response, much appreciated. It has got to be fatiguing continually articulating things at a "B" level, I don't take those efforts by everyone here for granted.

I just retired from 37 years of teaching undergrad physics at Elizabethtown College (not R1, I was paid to teach). I have always wanted to understand reality and felt that physics was the best way for me to do that (it's different for different people, obviously). When I figure something out, I love to explain it to people who want to understand, so answering your questions is a pleasure for me :-)

If it's possible to explain conceptually, what is new about the reconstruction that would make it more compelling vs prior constructions? Is it the concept that h-bar stays constant for all inertial frames be taken as an axiom?

What objections, if any, are you encountering?

The quantum reconstructions via information-theoretic principles are mathematically technical, it took me months to figure out the basics and I still have questions about some of the proofs (check out Hardy's original paper here). When I came to the simple understanding in the Insight, Markus Mueller invited me to present it at IQOQI in Vienna (April 2022). Caslav Brukner attended that presentation, checked what I said in the book, and then blurbed the book. I asked Markus, Hardy, and Grinbaum to check what I wrote about their reconstructions and reconstructions in general and all of them signed off (Markus had me add some references and the fact that his and Masanes' reconstruction was one of the "first fully rigorous, complete reconstructions").

Given that, I think it's safe to say that we have extended QM as a principle theory per the quantum reconstruction program (QRP) to a principle explanation a la SR. A principle theory (per Einstein) is a theory whose formalism is derived from an empirically discovered fact, e.g., thermodynamics from impossibility of making a perpetual motion machine and Lorentz transformations from light postulate. A principle explanation (per us) is a principle theory whose empirically discovered fact is justified by a compelling fundamental principle, e.g., light postulate justified by the relativity principle. To accomplish that we did two things:
1. Showed that the empirically discovered fact in the QRP that leads to the Hilbert space kinematics of QM (Information Invariance & Continuity) entails the observer-independence of h.
2. Justified that empirically discovered fact with the relativity principle (just like the light postulate is justified by the relativity principle, as shown in the Insight).

This addresses two concerns about the QRP (again, see our paper here):
1. As Goyal points out (2024), the elucidation of QM via its reconstruction is a two-step process, first you make the reconstruction, then you have to interpret it.
2. That's because, as Van Camp points out (2011):

nothing additional has been shown to be incorporated into an information-theoretic reformulation of quantum mechanics beyond what is contained in quantum mechanics itself. It is hard to see how it could offer more unification of the phenomena than quantum mechanics already does since they are equivalent, and so it is not offering any explanatory value on this front.

Since, as we explain, the relativity principle unifies QM and SR and is not "contained in QM itself," and it's already established as a compelling fundamental principle throughout physics, we have a compelling completion of the QRP. Now, to some objections about it.

The derivation of the Hilbert space kinematics does not address either the 'big' or 'small' measurement problems (MPs) because it says nothing about the dynamics of QM (needed to solve 'big' MP) and provides no ontology (needed to solve 'small' MP). We deflate both of those at length in Chapter 9 of the book and in summary at the end of this 2025 paper (also linked in the Insight). Of importance here is "all-at-once" explanation via adynamical global constraints per quantum-classical contextuality that does not violate locality (like Bohmian mechanics), statistical independence (like retrocausality or superdeterminism), intersubjective agreement (like QBism), or the uniqueness of experimental outcomes (like Many Worlds).

There is another complaint that we cannot address, i.e., personal preference. By moving the QRP firmly into spacetime (rotational and translational invariance of h) we have destroyed what some researchers believe was an advantage of the QRP, i.e., the removal of spatiality from measurement. Markus is among those who were hoping the despatialization of measurement would lead to a new approach to quantum gravity. We have a new approach to quantum gravity per quantum-classical contextuality, but it's not what they were considering via the despatialization of measurement, so they don't particularly like our completion.