Can free will possibly exist?

As far as I know, quantum physics does allow for "undecided" states. And then, Heisenberg's uncertainty principle means that even when everything is determined, it cannot be measured. Therefore, for all practical purposes, free will does exist. And it seems to me that human beings do act so unpredictably that it is not justified to compare them to pre-programmed machines. A fact that makes living as one difficult but also interesting.