Editing Light (section)

=== Quantum optics ===
{{main|Quantum optics}}
[[John R. Klauder]], [[George Sudarshan]], [[Roy J. Glauber]], and [[Leonard Mandel]] applied quantum theory to the electromagnetic field in the 1950s and 1960s to gain a more detailed understanding of photodetection and the [[Statistical mechanics|statistics]] of light (see [[degree of coherence]]). This led to the introduction of the [[coherent state]] as a concept which addressed variations between laser light, thermal light, exotic [[squeezed state]]s, etc. as it became understood that light cannot be fully described just referring to the [[electromagnetic field]]s describing the waves in the classical picture. In 1977, [[H. Jeff Kimble]] et al. demonstrated a single atom emitting one photon at a time, further compelling evidence that light consists of photons. Previously unknown quantum states of light with characteristics unlike classical states, such as [[Squeezed coherent state|squeezed light]] were subsequently discovered.

Development of short and [[Ultrashort pulse|ultrashort]] laser pulses—created by [[Q switching]] and [[modelocking]] techniques—opened the way to the study of what became known as ultrafast processes. Applications for solid state research (e.g. [[Raman spectroscopy]]) were found, and mechanical forces of light on matter were studied. The latter led to levitating and positioning clouds of atoms or even small biological samples in an [[optical trap]] or [[optical tweezers]] by laser beam. This, along with [[Doppler cooling]] and [[Sisyphus cooling]], was the crucial technology needed to achieve the celebrated [[Bose–Einstein condensation]].

Other remarkable results are the [[Bell test experiments|demonstration of quantum entanglement]], [[quantum teleportation]], and [[quantum logic gate]]s. The latter are of much interest in [[quantum information theory]], a subject which partly emerged from quantum optics, partly from theoretical [[computer science]].