cirq.von_neumann_entropy

Calculates the von Neumann entropy of a quantum state in bits.

cirq.von_neumann_entropy(
    state: 'cirq.QUANTUM_STATE_LIKE',
    qid_shape: Optional[Tuple[int, ...]] = None,
    validate: bool = True,
    atol: float = 1e-07
) -> float

The Von Neumann entropy is defined as \( - trace( \rho ln \rho)\), for a density matrix \(\rho\). This gives the amount of entropy in 'ebits' (bits of bipartite entanglement).

If state is a square matrix, it is assumed to be a density matrix rather than a (pure) state tensor.

state The quantum state.
qid_shape The qid shape of the given state.
validate Whether to check if the given state is a valid quantum state.
atol Absolute numerical tolerance to use for validation.

The calculated von Neumann entropy.

ValueError Invalid quantum state.

https://en.wikipedia.org/wiki/Von_Neumann_entropy