A skeptic of quantum theory explains his misgivings

In a 1905 paper, Albert Einstein proposed that light could travel in the form of particles later called photons. It was one of the pioneering papers in the research that led to quantum mechanics, the mathematical framework for describing matter and energy on a fundamental level. But in his later years, Einstein expressed grave dissatisfaction with quantum mechanics. He was especially unhappy with its description of reality in terms of probabilities, a view developed by the German physicist Max Born. Einstein preferred the deterministic cause-and-effect rigor of classical physics, expressing his displeasure by saying “God does not play dice.” But Einstein’s views on quantum mechanics are often oversimplified. For observable phenomena, he accepted the statistical view of quantum mechanics; his main concern was its incompleteness (in his view) in describing reality. To investigate those views, Science News Editor in Chief Tom Siegfried conducted an “interview” with Einstein via of a number of the physicist’s writings and statements.

Some physicists, among them myself, cannot … accept the view that events in nature are analogous to a game of chance. Oren Jack Turner/Library of Congress, Wikimedia Commons

In a nutshell, what’s wrong with quantum mechanics?

Some physicists, among them myself, cannot believe that we must abandon, actually and forever, the idea of direct representation of physical reality in space and time; or that we must accept the view that events in nature are analogous to a game of chance.

Why were you so upset about quantum theory when much of it was based on your own work?

Yes, I may have started it but I always regarded these ideas as temporary. I never thought that others would take them so much more seriously than I did.

Do you believe the world is totally deterministic, so each effect follows from its causes with complete predictability?

From the point of view of immediate experience there is no such thing as exact determinism…. The question is whether or not the theoretical description of nature must be deterministic. Beyond that, the question is whether or not there exists generally a conceptual image of reality (for the isolated case), an image which is in principle completely exempt from statistics.

Quantum mechanics has been extremely successful. How can you oppose a theory that always gets the right answers?

I consider the methods of quantum mechanics fundamentally unsatisfactory. I want to say straight away, however, that I will not deny that this theory represents an important, in a certain sense even final, advance in physical knowledge….  Probably never before has a theory been evolved which has given a key to the interpretation and calculation of such a heterogeneous group of phenomena of experience…. In spite of this, however, I believe that the theory is apt to beguile us into error in our search for a uniform basis for physics, because, in my belief, it is an incomplete representation of real things, although it is the only one which can be built out of the fundamental concepts of force and material points (quantum corrections to classical mechanics). The incompleteness of the representation leads necessarily to the statistical nature (incompleteness) of the laws.

So then are you saying that a statistical interpretation is necessary for observable “material points”?

Experiments lead to the conclusion that energy values lying between the quantum values do not exist…. It seems to be clear, therefore, that Born’s statistical interpretation of quantum theory is the only possible one.

David Bohm proposed a deterministic interpretation of quantum mechanics in 1952 — what about that?

That way seems too cheap to me.

You say that quantum statistics apply only to ensembles of systems rather than individual particles. Is it possible that nature allows no deeper insight into single systems than quantum mechanics provides?

To believe this is logically possible without contradiction; but, it is so very contrary to my scientific instinct that I cannot for­go the search for a more complete conception.

So do you believe quantum mechanics is not the final word as a basis for physical theory?

There is no doubt that quantum mechanics has seized hold of a good deal of truth, and that it will be a touchstone for any future theoretical basis…. If one wants to consider the quantum theory as final (in principle), then one must believe that a more complete description would be useless because there would be no laws for it. If that were so then physics could only claim the interest of shopkeepers and engineers; the whole thing would be a wretched bungle.

For sources of Einstein’s comments, visit www.sciencenews.org/einstein