Quantum mechanics is not explicitly discussed in the "Back to the Future" movies. The trilogy primarily focuses on the concept of time travel and the consequences of altering the past. The movies use a fictional device called the "flux capacitor" to enable time travel, but the explanation provided for its functioning is more in the realm of science fiction rather than quantum mechanics.
In the movies, the flux capacitor is described as a component that makes time travel possible by "fluxing" the "flux energy" through the "flux dispersal" and creating a "time field" that allows the DeLorean car to travel through time. These explanations are fictional and not based on the principles of quantum mechanics as understood in real-world physics.
However, it's worth mentioning that the concept of time travel does touch on some philosophical and scientific ideas that intersect with quantum mechanics, such as the possibility of multiple timelines or alternate realities. Still, the movies don't delve into the technical details or explicitly reference quantum mechanics in their explanations of time travel.