  We identify the time $T$ between Andreev reflections as a classical adiabatic
invariant in a ballistic chaotic cavity (Lyapunov exponent $\lambda$), coupled
to a superconductor by an $N$-mode point contact. Quantization of the
adiabatically invariant torus in phase space gives a discrete set of periods
$T_{n}$, which in turn generate a ladder of excited states
$\epsilon_{nm}=(m+1/2)\pi\hbar/T_{n}$. The largest quantized period is the
Ehrenfest time $T_{0}=\lambda^{-1}\ln N$. Projection of the invariant torus
onto the coordinate plane shows that the wave functions inside the cavity are
squeezed to a transverse dimension $W/\sqrt{N}$, much below the width $W$ of
the point contact.
