Single photon sources

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Single photon sources
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Approximate single photon source

• Attenuated laser
• Coherent state

Laser
Attenuator
Mean number of photon per pulse 0,1
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Pair photons and entangled photons
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Why photon pairs?

• Heralded single photon source

JGR,JMO 1998, 45, 595-604
Triggered APD
Heralded photons
Source of Photon pairs
Trigger photons
APD
Mandel (1986)
Experimental realization of a localized
one-photon state, C. K. Hong and L. Mandel, Phys.
Rev. Lett. 56, 58 (1986) Observation of
sub-poissonian light in parametric
downconversion. J.G. Rarity, P.R.Tapster and E.
Jakeman, Opt. Comm., 62(3)201, 1987.
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Creating Entangled Photon Pairs
C
Phase matching and energy conservation
D
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Portable Crystal based entangled pair
source150mW diode70000 detected coincidences/sec
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Recent experiments

• Free-Space distribution of entanglement and
  single
• photons over 144 km, R. Ursin, et al
  quant-ph/0607182

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Pair photon generation in microstructured
fibres With University of Bath

• Non-linear process in ?(3)
• 2 pump photons ? 2 emitted photons

Phase matching and energy conservation

• Use of the normal dispersion region
• no pump power dependence
• wavelengths created far from the pump
• Raman and fluorescence amplification effects
  reduced

W. J. Wadsworth et al. (Opt. Express 2004)
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Coincidences3.105 s-1
Spectra
Experiment
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Coincidence results
Idler (895nm) single-mode fiber
14 of coincidences Signal (583nm) multimode
fiber 33 of coincidences
single-mode fiber 22 of
coincidences
2 photon peak

• Ppump540µW
• Coincidence rate 3.5.105 s-1
• Overall coupling efficiency in SMF 60

4 photon peak
Confirmation of bright pair photon emission
-potential for 80 coupling to SMF
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Recent HOM Experiment
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Entangled state, preliminary measurement
Latest result by narrow band filtering 90 in HV
and 80 in /-45.