Editing Photon (section)

== Quantum optics and computation ==
Much research has been devoted to applications of photons in the field of [[quantum optics]]. Photons seem well-suited to be elements of an extremely fast [[quantum computer]], and the [[quantum entanglement]] of photons is a focus of research. [[Nonlinear optics|Nonlinear optical processes]] are another active research area, with topics such as [[two-photon absorption]], [[self-phase modulation]], [[modulational instability]] and [[optical parametric oscillator]]s. However, such processes generally do not require the assumption of photons ''per se''; they may often be modeled by treating atoms as nonlinear oscillators. The nonlinear process of [[spontaneous parametric down conversion]] is often used to produce single-photon states. Finally, photons are essential in some aspects of [[optical communication]], especially for [[quantum cryptography]].<ref>
Introductory-level material on the various sub-fields of quantum optics can be found in {{cite book |last=Fox |first=M. |url={{google books |id=Q-4dIthPuL4C |plainurl=y}} |title=Quantum Optics: An introduction |publisher=Oxford University Press |year=2006 |isbn=978-0-19-856673-1 |via=Google Books}}
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[[Two-photon physics]] studies interactions between photons, which are rare. In 2018, Massachusetts Institute of Technology researchers announced the discovery of bound photon triplets, which may involve [[polariton]]s.<ref name="NW-20180216">{{cite news |last=Hignett |first=Katherine |date=16 February 2018 |title=Physics creates new form of light that could drive the quantum computing revolution |magazine=[[Newsweek]] |url=http://www.newsweek.com/photons-light-physics-808862 |access-date=17 February 2018 |archive-date=25 April 2021 |archive-url=https://web.archive.org/web/20210425041617/https://www.newsweek.com/photons-light-physics-808862 |url-status=live }}</ref><ref name="SCI-20180216">{{cite journal |last1=Liang |first1=Qi-Yu |display-authors=etal |date=16 February 2018 |title=Observation of three-photon bound states in a quantum nonlinear medium |journal=[[Science (journal)|Science]] |volume=359 |issue=6377 |pages=783–786 |doi=10.1126/science.aao7293 |pmid=29449489 |pmc=6467536 |arxiv=1709.01478 |bibcode=2018Sci...359..783L }}</ref>