The relational interpretation of quantum physics

A reaction by a reader of my book mentioned that she didn’t find any mention of Carlo Rovelli’s relational quantum physics interpretation. Indeed. So I’ll repair that here. Rovelli sets his idea of relational quantum physics out in his recent book, Helgoland – Making sense of the Quantum Revolution. A book that should be read by everyone interested in the puzzling aspects of quantum physics. Rovelli is a good storyteller quite capable of keeping such a difficult subject interesting for the lay reader.

To me, his relational interpretation seems to say that all the material objects, that physics is about, only exist in relation to each other. They need each other to manifest their physical qualities. Without each other they are literally nothing.

The observer effect

With his relational interpretation Rovelli tries to explain the observer effect in quantum physics. That is the effect that the measurement of a quantum object gives the object its physical properties, such as location, speed en energy, which is the so-called quantum collapse. And also the effect that the way of observation determines in what way the objects will manifest itself. Before measurement the quantum objects has no physical properties. It does not exist in a material sense. It’s not there, not yet. Now you should realize that all objects in the world, including our own bodies, are in fact quantum objects.

That this is the case, has gradually become an inescapable conclusion for most physicists. The so-called delayed choice experiments have confirmed that before the measurement the measured particle does not yet exist physically. For a description of such an experiment carried out in 2007, I refer to my book, chapter 7 paragraph ‘The quantum eraser experiments’, or to the published article ‘Random Delayed-Choice Quantum Eraser via Two-PhotonImaging‘. Rovelli, in the introduction of his book, looking out at the sea, philosophizes with a colleague about this seeming absurd aspect of reality.

The hand in the interferometer

Rovelli describes in his book – chapter II around pages 45-46 – the surprising effect his hand evokes when he holds it in the path of a beam of photons in a Mach-Zehnder interferometer. This is a device where the incoming photons can travel along two different trajects that meet each other again at a beam splitter where interference occurs. If the device is properly configured and the photon can ‘travel’ unhindered along both roads, it turns out that interference happening at the second beam splitter causes the photons to be able only to leave the device in the direction of detector D1. It will only be detector D1 which detects photons. Detetector D2 detects nothing.

Mach-Zehnder interferometer, both trajects have equal lengths. All photons go to D1.

But when Rovelli blocks one of the two beam paths with his hand, and blocks thus half the photons, the unblocked photons, which have therefore traveled the lower path, suddenly arrive evenly distributed at both detectors.

Mach-Zehnder with hand blocking the upper path.

The photons that reach the second mirror apparently ‘know’ that Rovelli’s hand blocks the other path and can now freely choose between the two detectors. The big question is, how do they ‘know’ that?

Everything connected?

If you want to hold on to the image of a permanent objective world outside of us, then you can’t do much other than assuming that quantum objects are somehow connected to each other, that they have a relationship. Thus arrives Rovelli at his relational interpretation of quantum physics. But if you think a little further, then you will hopefully realize that this is a rather obfuscating technical term for the idea that everything is connected. And that is precisely the message that has reached us time and time again through Indian wisdom traditions, mystics, seers and – not unimportant – through reports of near death experiences.

The idea of a universe where objects only exist in relation to each other explains here the so-called quantum collapse, caused by the measuring instrument and also the undeniable observer effect that quantum physicists have been dealing with since the beginning of the last century. It is then not the awareness of the observer, but the fact that the observer is also a composition of quantum objects, which explains the observer effect. In my opinion, this is a variation of panpsychism, which says that everything is conscious. If you assume that everything is connected and ‘know’ where all the other objects are in the universe, which means awareness, then I do think the step is small to idealism, the idea that everything is actually happening within consciousness, a idea promoted these days strongly by – among many others – Bernardo Kastrup. Idealism is much simpler than making every separate object aware of all the others and therefore easier to understand than Rovelli’s panpsychism. Which does not mean that I even remotely understand what consciousness is, what it does and why, even though I experience it almost every moment.

The role of consciousness cannot be ignored, Quantum Physics confirms despite opposition

As regular readers of my posts and of my book will know, I am of the opinion that quantum physics does not so much prove the primary role of consciousness, however that it certainly strongly confirms it. This is of course a controversial position. As long as accepted science continues to cling to the materialistic frame of mind, there will be scientists who wholeheartedly try to show this as wrong. They want to maintain their there-is-only-matter vision, although the attractiveness of that idea of reality, in which I am only a casual bystander, escapes me. On top of that, there are also people who take consciousness and its survival after physical death seriously, but they prefer to keep quantum physics out of the whole discussion about consciousness.

Heisenberg’s uncertainty principle explained (?) by classic physics

The same goes for those two Finnish scientists who published a mathematical study in September 2020 in which Heisenberg’s uncertainty relation is a result of statistical fluctuations in space-time, somewhat comparable to the Brownian motion of microscopic particles in a liquid. These Finns, not quantum physicists by the way, would have shown that Heisenberg’s uncertainty relation is not a consequence of the measurement – the observation – of the particle, but is something that takes place entirely in the classical Newtonian world. One of the two authors, Jussi Lindgren, is not a mathematician but is a mathematically very educated person. This he states in his LinkedIn profile:

Part-time doctoral student at Aalto University School of Science, main interests in optimal control theory with applications in macroeconomics, physics and finance. Other academic interests include nuclear engineering and philosophy of science. Quantum physics, relativity and theoretical physics are key interests of mine as well.’

Their publication does indeed contain a impressive piece of complex mathematics. That is not particularly accessible to the layman who, despite his lack of mathematical skills, is interested in the true meaning of quantum physics.

Although my mathematical ability is not what it used to be, I would still like to add a critical note concerning their publication and especially their conclusion. Their conclusion is that the interpretation of quantum physics can be found within the classical Newtonian domain, ie hard objective scientific realism. The Heisenberg uncertainty relation says that there is a fundamental lower limit to the accuracy with which the position and speed of particles can be measured. According to these Finns, the particles in an experiment are permanently objectively present, but are controlled by statistical fluctuations in space-time that make it impossible to measure speed and position with an accuracy greater than Heisenberg’s principle allows. In fact, their approach is an excellently elaborated example of an the ensemble theory in quantum physics. Quantum ensemble theory is only about the statistical behavior of larger ensembles of particles and prefers to ignore the individual particle behavior itself. And therein lies the problem. Ignoring unwelcome facts is not science.

If we hadn’t had the Bell and the delayed choice experiments, I wouldn’t have been able to find good counter-arguments so easily. Their significance cannot be overstated. All Bell experiments have confirmed, with ever increasing confidence and without exception, that two (or more) particles, when they have a common history, are in such a way connected (entangled) that a measurement on one particle immediately makes the other particle exhibit the complementary property, while they did not have that property prior to the measurement. When you assume that those particles exist permanently and objectively, you cannot but assume then that the measured particle communicated faster than light to its entangled partner that it was measured, whereupon the partner ‘decided’ to show the complementary property. A property it did not have before measurement. Such an assumption, as far as I’m concerned, is far beyond what Occam’s Razor recommends us.

And then there are also (fortunately) the delayed choice experiments. These have shown very clearly that the idea of particles that are physically on their way from source to detector, and thus travel materially, cannot be correct, unless you make some rather far-fetched assumptions: about particles that can see into the future, about entangled photons that know that once the position of the other photon has been measured, they should adjust their behavior, showing or not showing interference or not, and, on top of that, retroactively in time. You are of course free to prefer the material view of the world, but then you have to be honest and accept intelligent and instantaneous behavior of elementary particles. Therefore I prefer the idea that it is ultimately the conscious observer who, when he observes an event, also records it for its history as a really happened event. My idea is that it is the conscious observer who is definitely not to be ignored if you really want to be scientific.

An experimental test of non-local realism

Last but not least, I would like to mention here the result of an experiment conducted at the University of Vienna in 2007, one that, in my opinion, has received little attention. In this experiment, the assumption that perception does not affect objective reality was actually tested. By this I do not mean that every measurement always disturbs that which is measured, that was already an accepted fact in classical physics, but that mere observation has an effect on the nature of the observed, although it does not physically touch what is observed. That is what is called a non-local influence.

In this experiment, a complete class of important non-local hidden variable hypotheses has been falsified. These theories presuppose realism. Permanently objectively existing matter. These hidden variable hypotheses propose mechanisms that would explain, for example, the entanglement of photons in Bell-type experiments with effects where they already possessed their polarization all along. They would not manifest it only at the moment of measurement.

The conclusion from this experiment is that we must take the result of a Bell-type experiment and its significance for what being real means, very seriously. We can no longer hope that science can repair the idea of objectively permanent matter of classic physics.