qiskit.quantum_info.purity¶
-
purity(state, validate=True)[source]¶ Calculate the purity of a quantum state.
The purity of a density matrix \(\rho\) is
\[\text{Purity}(\rho) = Tr[\rho^2]\]- Parameters
state (Statevector or DensityMatrix) – a quantum state.
validate (bool) – check if input state is valid [Default: True]
- Returns
the purity \(Tr[\rho^2]\).
- Return type
float
- Raises
QiskitError – if the input isn’t a valid quantum state.