Quantum optics

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Two photon interference

The interference of light was first studied by Thomas Young with his famous double slit experiment. This experiment showed first-order interference. Showed second-order interference of light and the first time experiment is by Hanbury Brown and Twiss using an intensity interferometer.[1]

Another type of interferometer which use the photon pairs from the spontaneous parametric down-conversion(SPDC) was built and used to show the quantum nature of light in 1987, which is called the 'Hong-Ou-Mandel dip' experiment.[2]

Fig.1. Geometry of the experiment



As shown in Fig.1, Generation of a photon pair is realized via parametric down conversion.Two photons where overlapped on a beam splitter spatially and temporally. The coincidence counts dropped down when the path lengths of the photons became identical.(Fig.2)

Fig.2. Single rate and coincident rate are measured for path delay


References:
  1. R.Hanbury Brown and Twiss, Nature (London) 177, 27-32 (1956)
  2. CK Hong, ZY Ou, L Mandel, Phys. Rev. Lett 59, 2044 (1987))url



Photon bunching

In recent years, there is an interesting subject of the study of the thermal nature in the process of spontaneous parametric down-conversion (SPDC)[1][2]. Since in this process photons from a pump laser beams are randomly converted into pairs of photons at lower frequency. Bunched light consists of a stream of photons with the photons all clumped together in bunches. In 1987, Yurke and Potasek have investigated the thermal nature of the field in one arm of a SPDC source)[3]. We will measure the photon statistics of weak light pulse emitted in the process of pulsed parametric down-conversion.


Fig.3 is the experimental setup

Fig.3. experimental setup



References:
  1. P.R.Tapster and J.G.Rarity, J.Mod.Optic,45,595(1998)
  2. B. Blauensteiner, I. Herbauts,S. Bettelli, etc. ArXiv: 0810.4785v1 [quant-ph], 27, 2008.
  3. B. Yurke and M. Potasek, Phys. Rev. A 36, 3464 (1987).
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