Von Neumann entropy

The von Neumann entropy of a quantum state ρ is given by the formula,

𝒮(ρ) ≡ −Tr(ρlog ρ)

and if λi are the eigenvalues of ρ then the Von Neumann entropy can be reexpressed as:

𝒮(ρ) = −∑iλilog (λi).

In quantum information the logarithms are usually taken to be base 2, giving a maximum entropy of 1 for a qubit.

See also

Category:Entropy Category:Handbook of Quantum Information

Last modified: 

Monday, October 26, 2015 - 17:56