Editing Squeezed coherent state (section)

==Experimental realizations==
There has been a whole variety of successful demonstrations of squeezed states. The first demonstrations were experiments with light fields using [[laser]]s and [[non-linear optics]] (see [[optical parametric oscillator]]). This is achieved by a simple process of four-wave mixing with a <math>\chi^{(2)}</math> crystal; similarly travelling wave phase-sensitive amplifiers generate spatially multimode quadrature-squeezed states of light when the <math>\chi^{(2)}</math> crystal is pumped in absence of any signal. [[Sub-Poissonian]] current sources driving semiconductor laser diodes have led to amplitude squeezed light.<ref>{{cite journal|last1=Machida|first1=S.|last2=Yamamoto|first2=Y.|last3=Itaya|first3=Y.|title=Observation of amplitude squeezing in a constant-current driven semiconductor laser|journal=Physical Review Letters|date=9 March 1987|volume=58|issue=10|pages=1000–1003|doi=10.1103/PhysRevLett.58.1000|bibcode = 1987PhRvL..58.1000M|pmid=10034306}}</ref>

Squeezed states have also been realized via motional states of an [[ion]] in a trap, [[phonon]] states in [[crystal lattice]]s, and spin states in neutral [[atom]] ensembles.<ref>O. V. Misochko, J. Hu, K. G. Nakamura, "Controlling phonon squeezing and correlation via one- and two-phonon interference," https://arxiv.org/abs/1011.2001</ref><ref>{{cite journal|last1=Ma|first1=Jian|last2=Wang|first2=Xiaoguang|last3=Sun|first3=C.P.|last4=Nori|first4=Franco|s2cid=119239234|title=Quantum spin squeezing|journal=Physics Reports|date=December 2011|volume=509|issue=2–3|pages=89–165|doi=10.1016/j.physrep.2011.08.003|arxiv = 1011.2978 |bibcode = 2011PhR...509...89M }}</ref> Much progress has been made on the creation and observation of spin squeezed states in ensembles of neutral atoms and ions, which can be used to enhancement measurements of time, accelerations, fields, and the current state of the art for measurement enhancement{{clarify|reason=In what setting? The claim is too broad.|date=September 2016}} is 20&nbsp;dB.<ref name="ReferenceA">{{cite journal|last1=Hosten|first1=Onur|last2=Engelsen|first2=Nils J.|last3=Krishnakumar|first3=Rajiv|last4=Kasevich|first4=Mark A.|s2cid=2139293|title=Measurement noise 100 times lower than the quantum-projection limit using entangled atoms|journal=Nature|date= 11 January 2016|volume=529|issue=7587|doi=10.1038/nature16176|pmid=26751056|pages=505–8|bibcode=2016Natur.529..505H}}</ref><ref>{{cite journal|last1=Cox|first1=Kevin C.|last2=Greve|first2=Graham P.|last3=Weiner|first3=Joshua M.|last4=Thompson|first4=James K.|s2cid=29467218|title=Deterministic Squeezed States with Collective Measurements and Feedback|journal=Physical Review Letters|date= 4 March 2016|volume=116|issue=9|doi=10.1103/PhysRevLett.116.093602|bibcode=2016PhRvL.116i3602C|pmid=26991175|page=093602|arxiv=1512.02150}}</ref><ref>{{cite journal|last1=Bohnet|first1=J. G.|last2=Cox|first2=K. C.|last3=Norcia|first3=M. A.|last4=Weiner|first4=J. M.|last5=Chen|first5=Z.|last6=Thompson|first6=J. K.|s2cid=67780562|title=Reduced spin measurement back-action for a phase sensitivity ten times beyond the standard quantum limit|journal=Nature Photonics|date=13 July 2014|volume=8|issue=9|pages=731–736|doi=10.1038/nphoton.2014.151|arxiv = 1310.3177 |bibcode = 2014NaPho...8..731B }}</ref><ref>{{cite journal|last1=Lücke|first1=Bernd|last2=Peise|first2=Jan|last3=Vitagliano|first3=Giuseppe|last4=Arlt|first4=Jan|last5=Santos|first5=Luis|last6=Tóth|first6=Géza|last7=Klempt|first7=Carsten|s2cid=38230188|title=Detecting Multiparticle Entanglement of Dicke States|journal=Physical Review Letters|date=17 April 2014|volume=112|issue=15|doi=10.1103/PhysRevLett.112.155304|arxiv = 1403.4542 |bibcode = 2014PhRvL.112o5304L|pmid=24785048|page=155304}}</ref> Generation of spin squeezed states have been demonstrated using both coherent evolution of a coherent spin state and projective, coherence-preserving measurements. Even macroscopic oscillators were driven into classical motional states that were very similar to squeezed coherent states. Current state of the art in noise suppression, for laser radiation using squeezed light, amounts to 15&nbsp;dB (as of 2016),<ref>{{Cite journal|last=Rini|first=Matteo|date=September 6, 2016|title=Synopsis: A Tight Squeeze|journal=Physics|volume=117|issue=11|pages=110801|doi=10.1103/PhysRevLett.117.110801|pmid=27661673|hdl=11858/00-001M-0000-002B-87B5-3|bibcode=2016PhRvL.117k0801V|arxiv=2411.07379}}</ref><ref name=":0">{{Cite journal|last1=Vahlbruch|first1=Henning|last2=Mehmet|first2=Moritz|last3=Danzmann|first3=Karsten|last4=Schnabel|first4=Roman|date=2016-09-06|title=Detection of 15 dB Squeezed States of Light and their Application for the Absolute Calibration of Photoelectric Quantum Efficiency|journal=Physical Review Letters|volume=117|issue=11|pages=110801|doi=10.1103/PhysRevLett.117.110801|bibcode=2016PhRvL.117k0801V|pmid=27661673|hdl=11858/00-001M-0000-002B-87B5-3|url=http://pubman.mpdl.mpg.de/pubman/item/escidoc:2351442/component/escidoc:2351441/PRL117_110801.pdf}}</ref> which broke the previous record of 12.7&nbsp;dB (2010).<ref>{{cite journal|last1=Eberle|first1=Tobias|last2=Steinlechner|first2=Sebastian|last3=Bauchrowitz|first3=Jöran|last4=Händchen|first4=Vitus|last5=Vahlbruch|first5=Henning|last6=Mehmet|first6=Moritz|last7=Müller-Ebhardt|first7=Helge|last8=Schnabel|first8=Roman|s2cid=9929939|title=Quantum Enhancement of the Zero-Area Sagnac Interferometer Topology for Gravitational Wave Detection|journal=Physical Review Letters|date=22 June 2010|volume=104|issue=25|doi=10.1103/PhysRevLett.104.251102|arxiv = 1007.0574 |bibcode = 2010PhRvL.104y1102E|pmid=20867358|page=251102}}</ref>