Say we have a stream of particles, emitted from a source, traveling freely in one direction and then colliding with some sort of screen. Between the source and the screen the particles are said to be in that indefinite state of limbo known as coherent superposition. Do the particles in this state, since they are not interacting with their environment (other particles), meet the definition of "conservative systems"? Conversely, does EVERY exchange of energy (interacting with other particles) constitute a "measurement"? As always, thanks in advance.