characterisation of non-classical light sources for quantum information technologies wojciech...
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Characterisation of non-classical light sources for quantum information technologies
Characterisation of non-classical light sources for quantum information technologies
Wojciech WasilewskiMichał KarpińskiPiotr Wasylczyk
Czesław RadzewiczFaculty of Physics
University of WarsawPoland
Piotr KolenderskiRobert FrankowskiKonrad BanaszekInstitute of PhysicsNicolaus Copernicus UniversityToruń, Poland
Parametric down-conversionParametric down-conversion
sp
i
Energy conservation:
Momentum conservation:
p = s + i
kp ks + ki
Twin beamsTwin beams
Fibre couplingFibre coupling
Fourier Transform SpectroscopyFourier Transform Spectroscopy
Common-path interferometerCommon-path interferometer
Joint spectrum measurementJoint spectrum measurement
W. Wasilewski, P. Wasylczyk, P. Kolenderski, K. B., and C. Radzewicz,Opt. Lett. 31, 1130 (2006)
InterferogramInterferogram
-100 -80 -60 -40 -20 0 20 40 60 80
-100
-80
-60
-40
-20
0
20
40
60
80
100
-100 -80 -60 -40 -20 0 20 40 60 80 100
-80
-60
-40
-20
0
20
40
60
80
100
Experiment vs. theoryExperiment vs. theory
Schmidt decompositionSchmidt decomposition
Mode pairsMode pairs
…what about the mode of one photon?
Two-photon interferenceTwo-photon interference
&
Probability amplitudes:
– + –
Photon indistinguishability =
mode matching
Coincidence probabilityCoincidence probability
&
Single pulseSingle pulse
t
t’
Double pulseDouble pulse
t
t’
Experimental schemeExperimental scheme
fLO
ALOr
t1 t2
&BS1 BS2
D2
D1M1
M2
W. Wasilewski, P. Kolenderski, and R. Frankowski,Phys. Rev. Lett. 99, 123601 (2007)
Simulated interferogramSimulated interferogram
Fourier transformFourier transform
Experimental setupExperimental setup
RegA
t1
t
X
FP C 50/ 50
D 1
D 2
I F
FC
D M
BGD M
I LFL
FC
PHW P
BS XSH
ND
W. Wasilewski, P. Kolenderski, and R. Frankowski,Phys. Rev. Lett. 99, 123601 (2007)
ResultsResults
Output wave functionOutput wave function
Fiber coupling:
Brigthness: Purity:
OptimizationOptimizationB
rig
htn
ess
Pu
rity
P. Kolenderski,W. Wasilewski, and K.B.,arXiv:0905.0009Phys. Rev. A (in press)
Geometric decorrelation:
A. U’Ren, K. B., and I. A. Walmsley, Quant. Inf. Comp. 3, 480 (2003).
Spectral filteringSpectral filtering
L = 1 mm, ws = wi = 100 mm, p = 100 fs
Multiphoton statisticsMultiphoton statistics
Losses
Multimode modelMultimode model
losses
losses Equivalent number of
(equally probable) modes
M
Squeezing strength r
Experimental setupExperimental setup
W. Wasilewski, C. Radzewicz, R. Frankowski, and K. Banaszek,Phys. Rev. A 78, 033831 (2008)
Two-beam photon statisticsTwo-beam photon statistics
Equivalent number of modesEquivalent number of modes
no filters 10 nm filters + 5 nm filters
Overall detection efficiencyOverall detection efficiency
no filters 10 nm filters + 5 nm filters
Contamination coefficientsContamination coefficients
Two-photon contaminationTwo-photon contamination
no filters 10 nm filters + 5 nm filters
Four-photon contaminationFour-photon contamination
No interference filters
Non-linear waveguideNon-linear waveguide
M. Karpiński, C. Radzewicz, and K.B.,Appl. Phys. Lett. 94,181105 (2009)
ConclusionsConclusions
• “Toolbox” for measuring spectral properties
• Modal structure an issue in multiphoton interference
• Spectral filtering sensible option for bulk sources
• Higher-order terms dangerous!