RE: Cats and quantum computers have more in common that one may think of…

The double slit experiment is very funny with this respect. You may want to have a look to this old post of mine.

The only true contradiction is to say that something both is and is not the case at the same time, for example "a particle is and is not in two places at the same time"

Another point is quantum mechanics is that it tells you that the position is not uniquely defined. Everything is probabilistic which is one of the complications in its understanding. Another complication is that a particle is a wave. That does not help.

In short, the quantum world is tough, but exciting!