Changes

Quantum wells work the other way round too.  If we attach a battery to the quantum well, then we give lots of electrical energy to the electrons and they are able to "climb" high up their ladder of energies.  Over time, they drop down the ladder and release bursts of energy of fixed sizes.  This energy is stored inside photons, meaning that a beam of light comes out of the quantum well.  Again, many useful devices have been made, including [[laser]]s and [[LED]]s.

Quantum wells work the other way round too.  If we attach a battery to the quantum well, then we give lots of electrical energy to the electrons and they are able to "climb" high up their ladder of energies.  Over time, they drop down the ladder and release bursts of energy of fixed sizes.  This energy is stored inside photons, meaning that a beam of light comes out of the quantum well.  Again, many useful devices have been made, including [[laser]]s and [[LED]]s.