Despite the triumph of Bell’s theorem, there have been a few serious attempts to apply the concept of hidden variables to get around the apparent lack of objective (observer-independent) reality at the quantum level. Interpretations of this type retain both objective reality and determinism, by postulating a real physical quantity or “force” that we have simply failed to measure directly.
Louis de Broglie called this factor a “pilot wave,” but abandoned his effort to develop a full-blown theory before completing it. More recently, David Bohm has developed perhaps the most complete theory of this type, wherein he postulates a quantum potential lurking alongside the real potential that we showed you in the Schroedinger equation. This quantum potential (or equivalently, this quantum force) guides the outcomes of all quantum measurements and thereby restores determinism.
QUANTUM LEAP
Louis de Broglie presented his idea of the pilot wave at the famous Solvay Conference of 1927. To his dismay, it resonated with his colleagues much less than he’d hoped. He was particularly disappointed by the fact that Albert Einstein didn’t offer any support. Unbeknownst to him at the time, this was because Einstein had himself pursued the idea a few months before only to abandon it shortly thereafter. Einstein was also unconvinced by Bohm’s expansion of the concept. In a 1952 letter to Max Born, he stated plainly that Bohm’s apparent solution “seems too cheap to me.”
The so-called de Broglie-Bohm interpretation of quantum physics is explicitly nonlocal, as required by Bell’s theorem and the Aspect experiment. The undetected quantum force guiding a given particle must depend on the state of any other particle with which it has interacted (or become entangled). Of course, some of those particles may be entangled with even more particles. Pretty soon it is clear that whatever this guiding force is, it must be affected by the whole universe all at once. Instead of being separable into individual particles and objects, the universe in a sense is just one big wave function. All of the different parts of the universe can affect all the other parts instantaneously.
DEFINITION
The de Broglie-Bohm interpretation of quantum physics speculates that there is a quantum potential that permeates space and allows for the hidden, nonlocal interactions needed to restore determinism.
This interpretation has some nice logical consistency, and does seem to be part of a trend toward a more holistic view of the universe—contrary to earlier tendencies to understand the world by understanding all of its parts separately. The fact that this view relies on a mysterious guiding force that can’t be (or hasn’t been) detected keeps it out of the mainstream for now.
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