De Broglie–Bohm theory
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The de Broglie–Bohm theory, also known as the pilot wave theory, Bohmian mechanics, and the causal interpretation, is an interpretation of quantum mechanics that postulates that, in addition to the wave function, a particle possesses a definite position at all times, even when unobserved.
The evolution over time of the configuration of all particles is defined by a guiding equation. The evolution of the wave function over time is given by the Schrödinger equation. The interpretation is named after Louis de Broglie and David Bohm.
The interpretation is deterministic and explicitly nonlocal: the velocity of any one particle depends on the value of the guiding equation, which depends on the configuration of all the particles under consideration.
Measurements are a particular case of quantum processes described by the theory—for which it yields the same quantum predictions as other interpretations of quantum mechanics. The interpretation does not have a "measurement problem", due to the fact that the particles have a definite configuration at all times. The Born rule in de Broglie–Bohm theory is not a postulate. Rather, in this theory, the link between the probability density and the wave function has the status of a theorem, a result of a separate postulate, the "quantum equilibrium hypothesis", which is additional to the basic principles governing the wave function. There are several equivalent mathematical formulations of the interpretation.