Math Moment

 

This is lesson 2 from IBM Learn Quatum Info. Having done some preparation,

I am actually following along and enjoying the lesson. When things aren't clear to

me or I'm just tired, I stop the video and work things through for myself...

Below, on tensor products. I initially have two systems (kets) X and Y that are bound

together, so that the sum of all possible states is 1. I measure X, which comes in at

0,  but not Y. What do I now know about the state of Y. That it now has the probabilities

of the initial X readings divided by the former's  probability for 1. The probabilities on Y

now sum to 1. All this from the math alone...