The probabilistic method uses arguments from probability to prove deterministic statements. This has been applied to diverse fields such as combinatorics, topology and number theory. In this method, you constructs a random variable based on the theorem that you want to prove. Using probabilistic arguments, you then show that the random variable has certain properties. From this the deterministic theorem follows.
I wonder if there is also a ‘quantum probabilistic method’. This would mean that you construct a (theoretical) quantum system based on a mathematical theorem that you want to prove. Then you prove that the quantum system must have certain properties, from which the mathematical theorem follows.