A quick note: in the first or second lecture when you multiply a state vector by a constant and use number 2 as an example, it's a bit confusing: it does not pr

A quick note: in the first or second lecture when you multiply a state vector by a constant and use number 2 as an example, it's a bit confusing: it does not preserve the unitarity. A better example would be a complex number exp(i\phi).