Editing Squeezed coherent state (section)

===Based on the presence of a mean field===
Squeezed states of light can be divided into squeezed vacuum and bright squeezed light, depending on the absence or presence of a non-zero mean field (also called a carrier), respectively. An [[optical parametric oscillator]] operated below threshold produces squeezed vacuum, whereas the same OPO operated above threshold produces bright squeezed light. Bright squeezed light can be advantageous for certain quantum information processing applications as it obviates the need of sending [[local oscillator]] to provide a phase reference, whereas squeezed vacuum is considered more suitable for quantum enhanced sensing applications. The [[LIGO#Advanced LIGO|AdLIGO]] and [[GEO600]] gravitational wave detectors use squeezed vacuum to achieve enhanced sensitivity beyond the standard quantum limit.<ref>{{cite journal | last1 = Grote | first1 = H. | last2 = Danzmann | first2 = K. | last3 = Dooley | first3 = K. L. | last4 = Schnabel | first4 = R. | last5 = Slutsky | first5 = J. | last6 = Vahlbruch | first6 = H. | s2cid = 3566080 | year = 2013 | title = First Long-Term Application of Squeezed States of Light in a Gravitational-Wave Observatory | journal = Phys. Rev. Lett. | volume = 110 | issue = 18| page = 181101 | doi=10.1103/physrevlett.110.181101| pmid = 23683187 | arxiv = 1302.2188 | bibcode = 2013PhRvL.110r1101G }}</ref><ref>{{cite journal | author = The LIGO Scientific Collaboration | year = 2011 | title = A gravitational wave observatory operating beyond the quantum shot-noise limit | journal = Nature Physics | volume = 7 | issue = 12| page = 962 | arxiv = 1109.2295 | bibcode = 2011NatPh...7..962L | doi = 10.1038/nphys2083 | s2cid = 209832912 }}</ref>