qiskit/quantum_info/operators/channel/transformations.py
def _reravel(mat1, mat2, shape1, shape2):
    """Reravel two bipartite matrices."""
    # Reshuffle indicies
    left_dims = shape1[:2] + shape2[:2]
    right_dims = shape1[2:] + shape2[2:]
    tensor_shape = left_dims + right_dims
    final_shape = (np.product(left_dims), np.product(right_dims))
    # Tensor product matrices
    data = np.kron(mat1, mat2)
    data = np.reshape(
        np.transpose(np.reshape(data, tensor_shape), (0, 2, 1, 3, 4, 6, 5, 7)),
        final_shape)
    return data
def _reravel(mat1, mat2, shape1, shape2):
    """Reravel two bipartite matrices."""
    # Reshuffle indicies
    left_dims = shape1[:2] + shape2[:2]
    right_dims = shape1[2:] + shape2[2:]
    tensor_shape = left_dims + right_dims
    final_shape = (np.product(left_dims), np.product(right_dims))
    # Tensor product matrices
    data = np.kron(mat1, mat2)
    data = np.reshape(
        np.transpose(np.reshape(data, tensor_shape), (0, 2, 1, 3, 4, 6, 5, 7)),
        final_shape)
    return data
Reravel two bipartite matrices.