qiskit.quantum_info.purity

purity(state, validate=True)

Calculate the purity of a quantum state.

The purity of a density matrix \(\rho\) is

\[\text{Purity}(\rho) = Tr[\rho^2]\]

パラメータ

• state (Statevector or DensityMatrix) – a quantum state.

• validate (bool) – check if input state is valid [Default: True]

戻り値

the purity \(Tr[\rho^2]\).

戻り値の型

float

例外

QiskitError – if the input isn’t a valid quantum state.