# Harmonic oscillator

why is the expectation value of the position of a harmonic oscillator in its ground state zero? and what does it mean that it is in ground state? is ground state equal to n=0 or n=1?

The energy can be calculated with the n quantum number, so that n = 0 corresponds to the energy of $1/2 \hbar \omega$. Answering your sencond question, n=0 corresponds to groud state.