# Wave Packet Dynamics

##
a
b

c

a) A displaced ground state of a simple harmonic oscillator of the correct
width (i.e., a **coherent state**) oscillates back and forth with constant width.

b) If the wave packet width or variance in a) is initially
**squeezed**, it will spread for a quarter of a cycle, then return to
the squeezed value at the half-cycle, spread for another quarter of a cycle,
and so on.

c) **Squeezed vacuum state**: the wave packet width or variance
is oscillating in a simple harmonic oscillator potential well. The
packet initially had a **squeezed variance**.

The paths traced by the oscillating packets as a function of time are also available as animations.

Expanded/Modified from: P. Meystre and M. Sargent III, *Elements of
Quantum Optics*, Springer-Verlag, 1991.