Editing Squeezed coherent state (section)

====Single-mode squeezed states====
Single-mode squeezed states, as the name suggests, consists of a single mode of the electromagnetic field whose one quadrature has fluctuations below the shot noise level {{clarify|reason=What is the "shot noise level"? A Poisson distribution?|date=September 2016}} and the orthogonal quadrature has excess noise. Specifically, a single-mode squeezed ''vacuum'' (SMSV) state can be mathematically represented as,
:<math> |\text{SMSV}\rangle =  S(\zeta)|0\rangle  </math>
where the squeezing operator S is the same as introduced in the section on operator representations [[#Operator representation|above]]. In the photon number basis, writing <math>\zeta = r e^{i\phi}</math> this can be expanded as,
:<math> |\text{SMSV}\rangle = \frac{1}{\sqrt{\cosh r}} \sum_{n=0}^\infty (- e^{i\phi} \tanh r)^n \frac{\sqrt{(2n)!}}{2^n n!} |2n\rangle</math>
which explicitly shows that the pure SMSV consists entirely of even-photon [[Fock state]] superpositions.
Single mode squeezed states are typically generated by degenerate parametric oscillation in an optical parametric oscillator,<ref>{{cite journal |first1=L.-A. |last1=Wu |first2=M. |last2=Xiao |first3=H. J. |last3=Kimble |title=Squeezed states of light from an optical parametric oscillator |journal=J. Opt. Soc. Am. B |volume=4 |pages=1465 |year=1987 |issue=10 |doi=10.1364/JOSAB.4.001465 |bibcode=1987JOSAB...4.1465W }}</ref> or using four-wave mixing.<ref name="slusher"/>