# von Neumann entropy

> English word · Noun · IPA /vɔn ˈnoɪ.mən ˈɛn.tɹə.pi/

## Definitions
1. The entropy of a quantum state. If the state is expressed as a quantum density matrix ρ, then this entropy can be expressed mathematically as S=-tr(ρ log ρ) where tr is the trace operator and the logarithm is natural.

## Etymology
Named after John von Neumann.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/von-neumann-entropy