Quantum resonance of the kicked rotor
= Quantum resonance of the kicked rotor
{title2=$\langle K\rangle_N=\hbar^2\eta^2N^2/(4I)$}
When the free angular-momentum <phases> all recur at the driving period, successive identical kicks add coherently. For the full revival $\hbar T/(2I)=2\pi$ and an initial zero-angular-momentum state, the <kinetic energy> after $N$ kicks is $\hbar^2\eta^2N^2/(4I)$. This ballistic law is specific to the stated <resonance> and <boundary conditions>.