cirq.bloch_vector_from_state_vector

Returns the bloch vector of a qubit.

cirq.bloch_vector_from_state_vector(
    state_vector: np.ndarray,
    index: int,
    qid_shape: (tuple[int, ...] | None) = None
) -> np.ndarray

Used in the tutorials
Classical control Textbook algorithms in Cirq

Calculates the bloch vector of the qubit at index in the state vector, assuming state vector follows the standard Kronecker convention of numpy.kron.

Args
`state_vector`	A sequence representing a state vector in which the ordering mapping to qubits follows the standard Kronecker convention of numpy.kron (big-endian).
`index`	index of qubit whose bloch vector we want to find. follows the standard Kronecker convention of numpy.kron.
`qid_shape`	specifies the dimensions of the qudits for the input `state_vector`. If not specified, qubits are assumed and the `state_vector` must have a dimension a power of two. The qudit at `index` must be a qubit.

Returns
A length 3 numpy array representing the qubit's bloch vector.

Raises
`ValueError`	if the size of `state_vector`is not a power of 2 and the shape is not given or if the shape is given and `state_vector` has a size that contradicts this shape.
`IndexError`	if index is out of range for the number of qubits or qudits corresponding to `state_vector`.

Args