von Neumann entropy

Meaning

Noun

• The entropy of a quantum state. If the state is expressed as a quantum density matrix $\backslash rho$, then this entropy can be expressed mathematically as $S\; =\; -\backslash text\{tr\}(\backslash rho\; \backslash log\; \backslash rho)$ where $\backslash text\{tr\}$ is the trace operator and the logarithm is natural.

Origin

• Named after John von Neumann.