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To clarify this crucial point of quantum mechanics, let me begin with a precise critique of my reading of it by Sašo Dolenc, a Slovene popularizer of science (whom I appreciate very highly)1: we are dealing here with a concise formulation of a reproach that is often made in a more diffuse way. To cut a long story short, according to Dolenc my mistake resides in my identification of relationality with incompleteness: from the fact that properties are not absolute (independent of their context), I wrongly conclude that reality is not determined. But relationality can be – and in physics also is – completely determined and real. The fact that an electron appears with a different spin if we change the axis of our measurement (its referential system) does not prove a lack in reality; it just proves the wealth of its relational potentials. A relational property is not simply a property of the object “in itself” but a property of the couple “object–referential system”2. With regard to the wave function, this means that it is a wholesome mathematical object which describes all possible correlations between events in time. When we choose today how we will measure a system, we merely choose which of the already existing correlations we will actualize. However, this idea of the wave function as a “wholesome mathematical object which describes all possible correlations between events in time” is by far not globally accepted in quantum theory: it gives preference to space over time – when in our time we just select a possibility, we merely actualize something already present in the timeless matrix of all possible options.
My first comment: the majority of quantum theorists deny the very possibility of imagining the totality of all possible correlations, not only due to our empirical limitation but already at the abstract theoretical level. Plus the idea that, in making a measurement, we choose one among the already existing possibilities secretly introduces a very problematic notion of (our) freedom – as if we were somehow at a distance from the “wholesome mathematical object” and were thus free to make different choices. Furthermore, in a proper quantum measurement, we choose a space of possible outcomes (defined by Schrödinger’s equation, which determines the probabilities of different results), and the individual result we get is contingent, unpredictable. This is why, if we repeat the same measurement with the same object, we get different results. This brings us to the basic ontological coordinates Dolenc attributes to quantum mechanics and contrasts with my notion of quantum mechanics. His basic premise is the dualism of quantum reality and our ordinary reality:
“The world is consistent both at the level of qubits and at the level of bits. The quantum state (qubit) is mathematically precise and physically real, just as classical information is real. The problem arises only at the transition. We cannot directly transfer or share quantum reality because we cannot copy it. To speak of it at all, we must translate it into bits. This translation is necessarily a reduction, but this reduction is not an ontological loss of substance, but an epistemological necessity of communication. The randomness that appears in this process is not proof that reality is missing something. Randomness is the tax we pay for conversion; it is the price for importing data from the quantum to the classical world. This is not a glitch in the system of reality, but a structural property of information itself: a qubit cannot pass into a bit without payment, and the currency of this payment is randomness.”
I agree that the problem arises at the transition, but in a much more radical sense than the one implied by Dolenc, who qualifies this transition (from the quantum domain to our ordinary reality) in two ways, both of which I find problematic. First, he qualifies it as the translation of the privacy of the quantum domain to the public domain of social communication: “If we want knowledge that can be shared, copied, and socially transmitted—if we want to cross from the privacy of the quantum to the publicity of the classical—we must accept the necessity of translation or measurement.” Second, he further qualifies the public domain as the domain of language, of communication: “Reality is full and rich at the level of qubits, but we cannot transfer this fullness forward. To be able to speak of it at all, we must translate it into bits.” Does this notion of quantum reality not reduce our ordinary reality to an effect of our epistemological limitation? Dolenc’s key claim is: “Qubits are what is; bits are what we can say.” So the only real reality is the quantum one, while what we experience as external reality is reality reduced through the filter of language. (Dolenc’s answer here would be that information itself is a material fact.)
