Hi @twang150 ,
Take a look at the image from the Codebook and the one from the documentation (first layer).
Do they look exactly the same? Or is something different?
If you focus on the two blocks from the documentation image, do they look the same too? Check the documentation in detail to answer this question, and you’ll find the answer to the challenge!
If it helps, you can try coding a small circuit on a separate notebook and drawing it with qml.draw_mpl().
I hope this helps you!