Macroscopic quantum state

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A macroscopic quantum state is a state of a system with many particles that cannot be described classically , but only correctly quantum-physically .

The quantum mechanics is used to describe the physics on a microscopic level, such. B. individual atoms or molecules . A quantum state usually only describes the properties of single or a few particles. The description of the properties of a system of very many particles on a macroscopic scale goes over into statistical or classical mechanics .

In a few special cases such as the state of superconductivity or superfluidity , which represent a new state of aggregation of substances, the properties of a macroscopic number of particles can no longer be explained by statistical or classical mechanics, but only by the laws of quantum physics . This always occurs when all particles are in the same quantum state (e.g. Bose-Einstein condensate ) and can therefore be described by a common wave function . One then speaks of a macroscopic quantum state.