Demonstrating app for the Billiard-ball Fredkin gate

This app was developed based on the description in Prof. Chris Bernhardt's book "Quantum Computing for Everyone". This Fredkin gate F(x,y,z) is equipped with several mirrors so that the billiard ball can be properly oriented. Also, appropriate delays are added to the paths so that the ball will collide when it should, and not when it does not. Here we can see the behavior of the two most complicated cases F(1,1,0) and F(1,1,1).

For more information, please see this article.

Acknowledgments

This app seems to work, but I'm not sure on some points.

First, for F(1,1,1), unlike F(1,1,0), I gave a delay to the start of ball 3 (input z). That's to make it properly collide with ball 2 within the switch gate.

Second, in the case of F(1,1,1), unlike the other cases, I gave a delay to the path of ball 1 (input x) outside the switch gate. This is to avoid collision with ball 2.

So, my question is:

As mentioned above, the delay is not the same for all input patterns. Is it acceptable to change the delay depending on the combination of inputs?

I would like to thank Prof. Chris Bernhardt for his good advice (2023-07-06).