Algorithmic cooling

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Algorithmic cooling is a phenomenon in quantum computation in which the processing of certain types of computation results in negative entropy and thus a cooling effect.

The phenomenon is a result of the connection between thermodynamics and information theory. In so far as information is encoded in physical systems it is subject to the laws of thermodynamics.

Certain processes within computation require a change in entropy within the computing system. As data must be stored as some kind of ordered structure (like a localized charge in a capacitor) so the erasure of data by destroying this order must involve an increase in disorder, or entropy. This means that the erasure of data releases heat. This is Landauer's principle.

Reversible computing or Adiabatic computing is a theoretical type of computing in which data is never erased, it just changes state or is marked to be ignored. In theory such a system would be able to "hide" data without releasing heat.

In the case of quantum entangled data, or qubits, it is possible for a computation to result in negative entropy, actually transferring heat out of the computational system, and so cooling it.