Quantum harmonic oscillator. Quantum mechanics, Harmonic oscillator, Equilibrium point, Quantum gravity, Nondimensionalization, Diatomic molecule, Canonical commutation relation, Particle in a spherically symmetric potential, Gas in a harmonic trap, Creation and annihilation operators, Coherent state, Morse potential, Hooke's atom, Bertrand's theorem, Grimsby, Solid-state physics.