  Parametric amplifiers are known to squeeze the vacuum state of the
electromagnetic field, which results in predictable statistics of the
photocounts at their output. However, recent theoretical work arXiv:1112.4159
predicts a very different statistical distribution for an amplifier based on a
Josephson junction. We test the hypothesis experimentally and recover the
expected squeezed vacuum statistics. We explain this discrepancy by showing
theoretically how the photocount statistics is dictated by the detection
process, from single mode (our experiment) to multimode, fully resolved in
frequency (as in arXiv:1112.4159).
