  Weak measurements in combination with post-selection can give rise to a
striking amplification effect (related to a large "weak value"). We show that
this effect can be understood by viewing the initial state of the pointer as
the ground state of a fictional harmonic oscillator, helping us to clarify the
transition from the weak-value regime to conventional dark-port interferometry.
We then describe how to implement fully quantum weak-value measurements
combining photons and atomic ensembles.
