Hidden variable theory
Under hidden variables or hidden parameters (hidden parameters ) is defined as occurring in some deterministic interpretations of quantum mechanics sizes, which physical reality is awarded and with the aid of the "pure " chance to be returned to the non-deterministic standard interpretation of quantum mechanics to deterministic mechanisms. Such interpretations are generally associated with a philosophical realism, so that such interpretations are also referred to as a realistic interpretations of quantum mechanics.
The parameters are hidden called because they do not show up in the standard interpretation of quantum mechanics and consequently no measurement method can be derived within this standard interpretation. If they exist, they would be so hidden in the standard interpretation. This does not mean that hidden variables could not in principle be measured. So can not be ruled out in principle, that of a deterministic theory with hidden variables, a measurement method can be derived. On the other hand, there are deterministic theories (such as the de Broglie -Bohm theory ) from which it can be shown that they do exactly the same empirical predictions as the nonrelativistic standard quantum mechanics, so that the hidden parameters are essentially unmeasurable.
We distinguish between theories with local and non-local hidden variables. Theories with local hidden variables always satisfy Bell's inequality. Quantum mechanics, however, injured in agreement with the results of the Aspect experiment (s Aspect experiment ) to the Einstein - Podolsky-Rosen paradox, Bell's inequality. Therefore, it can give no description of reality with local hidden variables.
The most common theory with non-local variables is the already mentioned de Broglie -Bohm theory. It is a deterministic theory in which the quantum mechanical wave function is considered " guide shaft " for unobservable particle trajectories. However, the de Broglie -Bohm theory is a nonrelativistic theory. A satisfactory extension to the relativistic case is still pending.