The Trouble with Quantum Mechanics... and a possible solution

Quantum Mechanics is still a mystery. It works perfectly in describing the properties of matter and light, and in developing novel technologies, yet no one understands what it is really about. The reason is that the Copenhagen interpretation assumes a division between the microscopic world governed by quantum rules and a macroscopic world of apparatus and observers that obeys classical physics. This division should not be part of a fundamental theory of nature, but removing it is not an easy task. I will discuss this problem, and will review some solutions that have been proposed to overcome it. In particular, I will present spontaneous wave function collapse models: they assume a new dynamics for physical systems in place of the Schrödinger equation, where the superposition principle progressively loses validity when moving from the micro- to the macro-world. I will show how this is implemented mathematically. I will discuss the physical consequences of the new dynamics, and the most promising experiments to test them, which span over a large variety of experimental platforms.