Editing Squeezed coherent state (section)

==Photon number distributions and phase distributions==
The squeezing angle, that is the phase with minimum quantum noise, has a large influence on the [[photon]] number distribution of the light wave and its [[phase (waves)|phase]] distribution as well.

{{multiple image
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 | image1   = photon numbers squeezed coherent states subpoisson.jpg
 | caption1 = Experimental photon number distributions for an amplitude-squeezed state, a coherent state, and a phase squeezed state reconstructed from measurements of the quantum statistics. Bars refer to theory, dots to experimental values.<ref name="Breitenbach">G. Breitenbach, S. Schiller, and J. Mlynek, "[http://gerdbreitenbach.de/publications/nature1997.pdf Measurement of the quantum states of squeezed light]", Nature, 387, 471 (1997)</ref>
 | image2   = phase distribution squeezed coherent states subpoisson.jpg
 | caption2 = Pegg-Barnett phase distribution of the three states
}}

For amplitude squeezed light the photon number distribution is usually narrower than the one of a coherent state of the same amplitude resulting in [[sub-Poissonian]] light, whereas its phase distribution is wider. The opposite is true for the phase-squeezed light, which displays a large intensity (photon number) noise but a narrow phase distribution. Nevertheless, the statistics of amplitude squeezed light was not observed directly with [[photon number resolving detector]] due to experimental difficulty.<ref>{{cite arXiv |title=Entanglement evaluation with Fisher information |eprint=quant-ph/0612099 |last1=kitagawa |first1=Akira |last2=Takeoka |first2=Masahiro |last3=Sasaki |first3=Masahide |last4=Chefles |first4=Anthony |year=2006 }}</ref>

[[File:photon numbers squeezed vacuum.jpg|thumb|400px|center|Reconstructed and theoretical photon number distributions for a squeezed-vacuum state.  A pure squeezed vacuum state would have no contribution from odd-photon-number states. The non-zero contribution in the above figure is because the detected state is not a pure state – losses in the setup convert the pure squeezed vacuum into a mixed state.<ref name="Breitenbach" /> (source: link 1)]]
For the squeezed vacuum state the photon number distribution displays odd-even-oscillations. This can be explained by the mathematical form of the [[squeezing operator]], that resembles the operator for [[Spontaneous parametric down conversion|two-photon generation]] and annihilation processes. Photons in a squeezed vacuum state are more likely to appear in pairs.