Constructive and destructive interference are generally well-understood and common phenomena even in the macro world. Sound waves, ocean waves, string instrume

Constructive and destructive interference are generally well-understood and common phenomena even in the macro world. Sound waves, ocean waves, string instruments. With QM, the probability can never be negative since it is calculated as the amplitude squared. Somewhat similarly, with ocean waves, we are not concerned that troughs are somehow creating negative energy when energy of an ocean wave = amplitude squared.