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.