  In the present article we use the quantum formalism to describe the effects
of risk and ambiguity in decision theory. The main idea is that the
probabilities in the classic theory of expected utility are estimated
probabilities, and thus do not follow the classic laws of probability theory.
In particular, we show that it is possible to use consistently the classic
expected utility formula, where the probability associated to the events are
computed with the equation of quantum interference. Thus we show that the
correct utility of a lottery can be simply computed by adding to the classic
expected utility a new corrective term, the uncertainty utility, directly
connected with the quantum interference term.
