Albert Einstein was critical of the de Broglie-Bohm theory, also known as the pilot wave theory or the Bohmian interpretation of quantum mechanics. This interpretation was developed by Louis de Broglie and David Bohm as an alternative to the standard Copenhagen interpretation of quantum mechanics.
One of Einstein's main concerns with the de Broglie-Bohm theory was its non-locality. The theory proposes the existence of a "pilot wave" that guides the behavior of quantum particles, determining their positions and velocities. According to this theory, particles possess definite positions even when not measured, which contrasts with the probabilistic nature of quantum mechanics as described by the Copenhagen interpretation.
Einstein, along with Boris Podolsky and Nathan Rosen, formulated a thought experiment known as the Einstein-Podolsky-Rosen (EPR) paradox to challenge the completeness of quantum mechanics. The EPR paradox suggests that quantum mechanics allows for non-local effects, meaning that the measurement of one particle can instantaneously affect the state of another particle, regardless of the distance separating them. This idea was at odds with Einstein's belief in a local, deterministic understanding of physics.
The de Broglie-Bohm theory provides a deterministic framework for quantum mechanics, but it relies on non-local influences, as particles are guided by the pilot wave. Einstein found this non-locality conceptually problematic and famously referred to it as "spooky action at a distance."
It is important to note that Einstein's criticisms were philosophical and based on his deep-seated preference for a deterministic, local understanding of physical phenomena. However, subsequent experimental tests and theoretical developments, such as Bell's theorem and the violation of Bell's inequalities, have provided strong evidence in favor of non-local effects in quantum mechanics.
While Einstein's concerns with the de Broglie-Bohm theory were valid in terms of his philosophical preferences, the theory remains a legitimate interpretation of quantum mechanics, and it has its own community of researchers who continue to explore its implications and applications.