  In order to know if the Schrodinger's cat is alive or dead without opening
the box, observers have to play a game with nature. The observers have to
"guess" (with degrees of belief) the state of the cat due to incomplete
information; in other words, the observers' decision has to be made under
uncertainty. We propose a quantum expected value theory for decision-making
under uncertainty. Value operator is proposed to guide observers to choose
corresponding actions based on their subjective beliefs through objective
quantum world by maximizing the value from the measured historical results. The
value operator, as a quantum decision tree, can be constructed from both
quantum gates and logic operations. Genetic programming is applied to optimize
quantum decision trees.
