Physics:Quantum Commutator



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In quantum mechanics, a commutator measures how much two operators fail to commute. For two operators $A$ and $B$, the commutator is

$[A,B]=AB-BA.$

A commutator compares doing two quantum operations in different orders.

Role in quantum mechanics

Commutators are central because quantum observables are represented by operators. If two observables have a nonzero commutator, the corresponding quantities generally cannot both have sharply defined values in the same state.

The canonical position and momentum commutator is

$[x,p]=i\hslash I.$

This relation underlies the uncertainty principle and is one of the basic structures of matrix mechanics.

See also

• Physics:Quantum mechanics
• Physics:Quantum Matrix mechanics
• Physics:Quantum Uncertainty principle
• quantum operators
• quantum observables

References

• "Commutator". https://mathworld.wolfram.com/Commutator.html. 
• Dirac, P. A. M. (1930). The Principles of Quantum Mechanics. Oxford University Press. 

Author: Harold Foppele