qiskit/quantum_info/states/states.py
def purity(state):
    """Calculate the purity of a quantum state.

    Args:
        state (ndarray): a quantum state
    Returns:
        float: purity.
    """
    rho = np.array(state)
    if rho.ndim == 1:
        return 1.0
    return np.real(np.trace(rho.dot(rho)))
def purity(state):
    rho = np.array(state)
    if rho.ndim == 1:
        return 1.0
    return np.real(np.trace(rho.dot(rho)))
def purity ( state ) : rho = np . array ( state ) if rho . ndim == 1 : return 1.0 return np . real ( np . trace ( rho . dot ( rho ) ) )
Calculate the purity of a quantum state.

    Args:
        state (ndarray): a quantum state
    Returns:
        float: purity.
Calculate the purity of a quantum state .