Measuring the Wave-Function of Broadband Bi-Photons

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Measuring the Wave-Function of Broadband
Bi-Photons
FRISNO 2013, Ein Gedi

• Yaakov Shaked, Roey Pomeranz, Avi Peer
• Rafi Vered, Lena Kirjner, Michael Rosenbluh
• Physics Dept. and BINA center for nanotechnology,
  Bar Ilan University

ISF, EU-IRG, Kahn Foundation
How to make a TiSapphire laser tap-dance
Posters M17, T23
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Outline

• Why ultra broadband photon pairs?
• Measuring time-energy entanglement
• HOM interference
• SFG correlation
• Measuring the two-photon phase with quantum
  pairwise interference
• Non-classical nature Fringe contrast
• FWM Observe the entire quantum-to-classical
  transition

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Time-Energy Entangled Photons
non linear crystal
pump
signal
idler
The two-photon state (monochromatic pump)
Entanglement
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Time-Energy Correlation
uncertainty relation
the two-photon wave function (monochromatic pump)
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Ultra-Broadband bi-Photons
Zero Dispersion !
Single cycle bi-photons
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Why ultra-broad photon pairs ?
Because there are so many of them !
Standard detection does not work Need new schemes
!
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Measuring entanglement - HOM

• Limitations
• Phase sensitivity, but no phase measurement
• Only for indistinguishable photons
• Not directly applicable for collinear
  configuration

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Measuring entanglement - SFG
PRL 94, 043602 (2005) , PRL 94, 073601 (2005)
Efficient two-photon interaction

• Limitations
• Phase sensitivity, but no phase measurement
• Very low SFG efficiency ! (10-8)

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Quantum two-photon interference
What if we let the pump pass ?
Frustrated Two-Photon Creation via Interference"
, T. J. Herzog, J. G. Rarity, H. Weinfurt A.
Zeilinger, Phys. Rev. Lett. 72, 629-632 (1993).
CCD camera
Pump laser (880nm)
Crystal 2
Crystal 1
Pump power meter
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SFG efficiency 60Inherent phase stability !
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Reconstruct the spectral phase

• Phase mismatch
• Dispersion from the dielectric mirrors

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What is non-classical ?
Classical fringe contrast
A
CCD camera
Pump laser (880nm)
B
Crystal 2
Crystal 1
Pump power meter
A
Measure of the two-photon purity
B
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Now to FWM
Four Waves Mixing
Down conversion
non linear fiber
non linear crystal
pump
signal
signal
pump
idler
idler
?i
energy conservation
2?p
?s
ki
ks
momentum conservation (phase matching)
2kp
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The Experiment
6ps
TiS Laser (6ps)
PCF
Spontaneously generated signal-idler (ASE)
Spectrometer
Pump filter
Different from supercontinnum generation!
INCOHERENT No comb
Dispersive window
Unique regime compared to CW High gain
Can cover the full Quantum-Classical transition
Rafi Z. Vered, Michael Rosenbluh, and Avi Peer,
Two-photon correlation of broadband-amplified
spontaneous four-wave mixing, Phys. Rev. A 86,
043837 (2012)
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FWM and TWM Differences
Four Waves Mixing
Down conversion
Rescale equations
Generalized phase mismatch
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FWM Gain Solution
Signal/idler solution
Similar to 3-waves, but
Gain only when ?klt0 !
Correlation ?
Gain also when ???0 !
Threshold pump intensity !
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FWM results (Fresh)
At zero dispersion - 784nm (?k0)
Full Quantum-classical transition !
788nm
786nm
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Conclusions

• A source of collinear single cycle bi-photons
• Huge Homodyne Gain in two-photon efficiency
  (40) with pump inserted into the 2nd crystal
• Holographic measurement of the spectral phase of
  the bi-photons by pairwise interference
• Fringe contrast is a quantum signature Measure
  quantum correlation by trying to undo it
• Observation of the entire classical-quantum
  transition with FWM in fiber
• Inherently stable collinear interferometer No
  locking needed
• Many things we dont understand yet