What is the right interpretation to give to quantum mechanics?

An explanation at all costs?

Physicists pay little attention to the interpretation of quantum mechanics on a daily basis. The Standard Model works very well, even to the point that researchers hope for unexpected results from their experiments that would force new theoretical developments. That quantum mechanics is difficult to connect to the macroscopic is not really a concern. Scientific disciplines are compartmentalized, but the real world is unified. It does not matter that some of our representations are incompatible with each other, they correctly describe each slice of reality concerned. Even if they connect by fragile correlations, reality seems able to hold the whole upright. Knowing how is just a matter of tenacity.

Don’t philosophers seem a little hysterical to worry about incompatibilities between models that do not directly overlap? They are agitating as if the world is going to fall apart because of the flaws in its representation. But no, it holds. Its substance seems immutable. Thus unmasks a difference between the mind of the philosopher and that of the scientist:

Philosophical vs. scientific mind

The philosopher’s mind is centered on the Spirit pole —I call the part of the mind that represents the self. It seeks to bring the world to oneself. It is therefore necessary that all the representations of the world are organized to form a unified, coherent entity. To endure a crack in the building would be to accept a rift in the Self. Irreducible mystery, inability to merge with the world, realistic neurosis, let’s call this discomfort what we want, but it is an obvious target for the Spirit pole, which invents a wide variety of metaphysical cements to join its fragments of representation.

The scientist’s mind is centered on the Real pole —the part of the mind that represents the non-self. The real does not ask itself any question about its being. Neither does the Real pole. It is. All that remains is to explain. Not finding an explanation, at the moment, is not stressful. This does not call into question the fact of being. The explanation will inevitably fall. No need to rush things. Finding is a process that, like reality itself, inevitably comes to an end. The scientist is already, in the present, on the path to success. While the philosopher, placed at the end of the road – that of a unified world – worries at the slightest slippage about whether the world comes to her.

This description is caricatured, like all generalizations. We all have Spirit and Real poles. The more they dialogue, the more scientific the philosopher is and vice versa. The contemporary philosopher will look in science why the world does not come to her, and the physicist adapts her models to make them cross the threshold of her discipline.

The quantum black box

It is with this dialogue in mind that we must appreciate the competing interpretations of quantum mechanics. La Recherche has just published a remarkable file on the subject. The space is given generously to philosophers of science as well as scientists, and the result is very homogeneous. Antoine Tilloy, physicist, shows the limits of the “black box” attitude for the interpretation of quantum within the macroscopic. Simply connecting initial conditions and result by a mathematical model is not an explanation. It is an instrumentalism pushed to the extreme that becomes anti-realism: it says nothing about the essence of reality and tries to replace it.

Baptiste Le Bihan, philosopher, goes on to validate for physics the possibility of demonstrating the existence of parallel universes. Mutual support between philosopher and physicist. Let’s look at the detail, however, because Baptiste mixes different hypotheses of multiverse that do not have the same realism.

Interpretation: the real candidates

He brings together the model of eternal inflation in cosmology, Everett’s multiple worlds, and alternative universes with string theory. They are not the same multiverses, and not the same infinities. Cosmological and string multiverses are juxtapositions of independent universes. Everett’s is an infinity without any measure with others, and without any way to separate the world of our experience. It is immeasurably more “romantic” than the others, to use John Bell’s terminology. Bell was indicating that a good theory does not need to add a surprising character to the world that is not strictly imposed by experiments. Experiments have imposed quantum oddity, which rests on a precise mathematical foundation. No experiment or equation leads to Everett’s multiverse in any inescapable way. Its romanticism puts it out of the game in the face of competing interpretations.

Two remain in the running: the pilot wave (Broglie-Bohm theory) and especially the objective collapse models. The pilot wave has the advantage of perfectly respecting the Schrödinger wave function. Advantage that is also its disadvantage: no experience allows to distinguish it from other interpretations with the current means. Moreover, the pilot wave only pushes back into the depths of reality the strange wave-corpuscle association, without explaining it. Isn’t getting rid of the counterintuitive in the unknown also romanticism according to Bell?

Objective collapse

Objective wave packet reduction models, or objective collapse, modify the Schrödinger equation very slightly by adding background noise related to neighboring particles. Without consequence on the dynamics of a few particles, it radically changes the equation on a large scale, when a macroscopic number of particles is involved. The wave function tightens around a point. It becomes corpuscle when it interacts with a large number of others. We find the classic matter.

The interpretation of objective collapse has two considerable advantages: 1) It is testable. The collapse of the wave packet by this means produces a very small amount of radiation that does not exist with the classical Schrödinger function. It is therefore possible to differentiate it, which is underway at the Italian laboratory of Gran Sasso. 2) The objective collapse fits perfectly into Surimposium, the more general theory of reality that I defend on this site.

Surimpose to not eliminate

In this theory, each level of complexity constructs its framework and rules in relative independence from its constitution. Correlation yes, determinism no, due to the approximation made by the emerging level on its constitution. For example, the temperature and pressure of a gas do not change, for what interacts with the gas, while countless microphysical constitutions of the gas follow one another continuously. Similarly, the characteristics of a corpuscle of matter do not change, for the other corpuscles forming a system with it, while the potentialities of the wave packet are always present in its constitution.

In this theory it is not necessary to reduce the wave function. No need to eliminate all probabilities except one. They still exist at the underlying, constitutive level of the quanton. Macroscopic interaction adds an organization of wave packets. One of the probabilities emerges, surimposes itself on the others without making them disappear. The independence of complexity levels allows them to exist together (let’s avoid saying ‘simultaneously’ because time frames are specific to each level).

We are at the same time waves, corpuscles, cells and even the mind, without seeing one replacing the fact of having seen the other. To interpret is not to manufacture a world of ideals parallel to reality, it is to encompass one interpretation in another in a perfectly concrete, physical way. It is also to extract oneself from the horizontal sequential way of thinking and verticalize our models.

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