Editing Coherence (physics) (section)

=== Matter wave coherence ===
The simplest extension of optical coherence applies optical concepts to [[matter waves]]. For example, when performing the [[double-slit experiment]] with atoms instead of light waves, a sufficiently collimated atomic beam creates a coherent atomic wave-function illuminating both slits.<ref name=adams>{{Cite journal |last1=Adams |first1=C.S |last2=Sigel |first2=M |last3=Mlynek |first3=J |date=May 1994 |title=Atom optics |journal=Physics Reports |language=en |volume=240 |issue=3 |pages=143–210 |doi=10.1016/0370-1573(94)90066-3|doi-access=free |bibcode=1994PhR...240..143A }}</ref> Each slit acts as a separate but in-phase beam contributing to the intensity pattern on a screen. These two contributions give rise to an intensity pattern of bright bands due to constructive interference, interlaced with dark bands due to destructive interference, on a downstream screen. Many variations of this experiment have been demonstrated.<ref name=cronon>{{Cite journal |last1=Cronin |first1=Alexander D. |last2=Schmiedmayer |first2=Jörg |last3=Pritchard |first3=David E. |date=2009-07-28 |title=Optics and interferometry with atoms and molecules |url=https://link.aps.org/doi/10.1103/RevModPhys.81.1051 |journal=Reviews of Modern Physics |language=en |volume=81 |issue=3 |pages=1051–1129 |doi=10.1103/RevModPhys.81.1051 |arxiv=0712.3703 |bibcode=2009RvMP...81.1051C |issn=0034-6861|hdl=1721.1/52372 |s2cid=28009912 |hdl-access=free }}</ref>{{rp|1057}}

As with light, transverse coherence (across the direction of propagation) of matter waves is controlled by collimation. Because light, at all frequencies, travels the same velocity, longitudinal and temporal coherence are linked; in matter waves these are independent. In matter waves, velocity (energy) selection controls longitudinal coherence and pulsing or chopping controls temporal coherence.<ref name=adams />{{rp|154}}