def multiply_matrix()

in src/braket/default_simulator/linalg_utils.py [0:0]

• 11 lines of code
• 3 McCabe index (conditional complexity)

def multiply_matrix(state: np.ndarray, matrix: np.ndarray, targets: Tuple[int, ...]) -> np.ndarray:
    """Multiplies the given matrix by the given state, applying the matrix on the target qubits.

    Args:
        state (np.ndarray): The state to multiply the matrix by.
        matrix (np.ndarray): The matrix to apply to the state.
        targets (Tuple[int]): The qubits to apply the state on.

    Returns:
        np.ndarray: The state after the matrix has been applied.
    """
    gate_matrix = np.reshape(matrix, [2] * len(targets) * 2)
    axes = (
        np.arange(len(targets), 2 * len(targets)),
        targets,
    )
    product = np.tensordot(gate_matrix, state, axes=axes)

    # Axes given in `operation.targets` are in the first positions.
    unused_idxs = [idx for idx in range(len(state.shape)) if idx not in targets]
    permutation = list(targets) + unused_idxs
    # Invert the permutation to put the indices in the correct place
    inverse_permutation = np.argsort(permutation)
    return np.transpose(product, inverse_permutation)