In this video I will explain how the quantum mechanic oscillator hold on to and increase its energy. Just like a classical oscillator that oscillates back and forth between a minimum (x=-A) and maximum (x=A) amplitude, and the frequency is sqrt(k/m) which is a constant. So if the amplitude and the frequency are fixed constants, then the only way for the energy to increase in a quantum mechanic oscillator is the addition of a photon.