Does Quantum Mechanics Require a Conscious Observer?

 

The notion that the interpretation of quantum mechanics requires a conscious observer is rooted, I believe, in a basic misunderstanding of the meaning of a) the quantum wavefunction ψ, and b) the quantum measurement process. This misunderstanding originated with the work of John von Neumann (1932) on the foundations of quantum mechanics, and afterwards it was spread by some prominent physicists like Eugene Wigner (1984); by now it has acquired a life of its own, giving rise to endless discussions on this subject, as shown by the articles in the Journal of Cosmology (see volumes 3 and 14).

Quantum mechanics is a statistical theory that determines the probabilities for the outcome of a physical process when its initial state has been determined. A fundamental quantity in this theory is the wavefunction ψ which is a complex function that depends on the variables of the system under consideration. The absolute square of this function, ψ2, gives the probability to find the system in one of its possible quantum states. Early pioneers in the development of quantum mechanics like Niels Bohr (1958) assumed, however, that the measurement devices behave according to the laws of classical mechanics, but von Neumann pointed out, quite correctly, that such devices also must satisfy the principles of quantum mechanics. Hence, the wavefunction describing this device becomes entangled with the wavefunction of the object that is being measured, and the superposition of these entangled wavefunctions continues to evolve in accordance with the equations of quantum mechanics. This analysis leads to the notorious von Neumann chain, where the measuring devices are left forever in an indefinite superposition of quantum states. It is postulated that this chain can be broken, ultimately, only by the mind of a conscious observer.

I present, tongue in cheek, the von Neumann paradox as a dilemma: The experiment may be said to start with the printed proposal and to end with the issue of the report. The laboratory, the experimenter, the administration, and the editorial staff of the Physical Review are all just part of the instrumentation. Tee! Hee! Hee! The incorporation of (presumably) conscious experimenters and editors into the equipment raises a very intriguing question... If the interference is destroyed, then the Schrodinger equation is incorrect for systems containing consciousness. If the interference is not destroyed, the quantum mechanical description is revealed as not wrong but certainly incomplete (Bell and Nauenberg, 1966). I have added the remark that “we emphasize not only that our view is that of a minority, but also that current interest in such questions is small. The typical physicist feels that they have been long answered, and that he will fully understand just how, if ever he can spare twenty minutes to think about it.”

Now the situation has changed dramatically, and interest in a possible role of consciousness in quantum mechanics has become widespread. But Bell, who died in 1990 , believed in the second alternative to the von Neumann dilemma, remarking that: I think the experimental facts which are usually offered to show that we must bring the observer into quantum theory do not compel us to adopt that conclusion (Davies and Brown, 1986). Actually, by now it is understood by most physicists that von Neumann’s dilemma arises because he had simplified the measuring device to a system with only a few degrees of freedom, e.g. a pointer with only two states. Instead, a measuring device must have an exponentially large number of If the wavefunction ψ is a physical object like an atom, then the proponents of this flawed concept must require the existence of a mechanism that lies outside the principles governing the time evolution of the wavefunction ψ in order to account for the so-called “collapse” of the wavefunction after a measurement has been performed. But the wavefunction ψ is not a physical object like, for example, an atom which has an observable mass, charge and spin as well as internal degrees of freedom. Instead, ψ is an abstract mathematical function that contains all the statistical information that an observer can obtain from measurements of a given system. In this case there isn’t any mystery that its mathematical form must change abruptly after a measurement has been performed. For further details on this subject, see (Nauenberg, 2007) and (van Kampen, 2008). The surprising fact that mathematical abstractions can explain and predict real physical phenomena has been emphasized by Wigner (Wigner 1960), who wrote: The miracle of appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve.

© Gene Vincent  2022

Originally published in West Ruislip Pensioners' Voice