In quantum mechanics, orientation entanglement refers to a specific type of entanglement between the quantum states of particles with angular momentum or spin. When two or more particles are entangled in terms of their orientations, measuring the orientation of one particle instantaneously determines the orientation of the other, regardless of the distance between them.
The key difference between orientation entanglement in quantum mechanics and classical physics lies in the nature of the correlations and the limitations of measurement. In classical physics, the orientations of objects are typically described using well-defined, deterministic variables. For example, the orientation of a spinning top can be precisely determined by its angular momentum vector, and measuring its orientation at one point in time does not instantaneously determine the orientation of another spinning top elsewhere.
However, in quantum mechanics, the orientation of a particle, such as its spin, is described using quantum states. These states can exhibit a peculiar property called superposition, where a particle can exist in multiple states simultaneously. When particles are entangled in terms of their orientations, their quantum states become correlated, and measuring the orientation of one particle will instantaneously determine the orientation of the other particle, even if they are far apart.
This non-local correlation in quantum mechanics is fundamentally different from the classical notion of orientation. It is a consequence of the wave-like nature of quantum particles and the superposition principle, which allows for entanglement and the instantaneous collapse of the entangled states upon measurement.
Experimental tests of orientation entanglement, such as the famous Bell's theorem experiments, have confirmed the non-classical nature of entanglement and its violation of certain classical assumptions, known as Bell inequalities. These experimental results support the unique and non-intuitive features of quantum mechanics compared to classical physics.