ilja gerhardt, matthew p. peloso , caleb ho, antía lamas-linares and christian kurtsiefer
DESCRIPTION
CQT. QUANTUM OPTICS. GROUP. Entanglement-based Free Space Quantum Cryptography in Full Daylight. Ilja Gerhardt, Matthew P. Peloso , Caleb Ho, Antía Lamas-Linares and Christian Kurtsiefer. Introduction to QKD. Quantum Cryptography = Quantum Key Distribution - PowerPoint PPT PresentationTRANSCRIPT
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Ilja Gerhardt, Matthew P. Peloso, Caleb Ho, Antía Lamas-Linares and Christian Kurtsiefer
Entanglement-based Free Space Quantum Cryptography in Full Daylight
QUANTUM OPTICSCQTGROUP
Centre fo rQu ant umTechn o lo gies , Sing a p o re
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Introduction to QKD• Quantum Cryptography =
Quantum Key Distribution–Have a Random Number at two
locationsOne-time pad for encryption
• 1980ies: Prepare and Send–Bennet Brassard, BB84–Send single Photons, non-cloning
theorem• 1990ies: Entanglement Based…
why?
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Prepare and Send• Need for Random Numbers
• Different Photons, different Colors?–Dimensionality of Hilbert space needs to
be known for security
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Entanglement based QKD• Ekert 1991 (E91)
–Let’s measure two qubits of an entangled entity
–Perfect (Anti)correlation–Bell’s inequality violated= eavesdropper knowledge can be
eliminated via PA
• Photons for convenience…• Freespace: Ad-hoc set-up
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Entanglement based QKD• Pairsource: BBO, lean & compact
–Strong temporally correlated –Broader than dimmed lasers
19’’10’’
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Detection of Photons
50:50 PBS
PBS
APD, +45°
l/222.5
°
V
-45°H
• Detection: Polarization analyzer
J.G. Rarity et al., J. Mod. Opt. 41, 2345 (1994)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Setup
P B S
R b
H WB S P B S
T U
P C
Bo btelesco peSending
telesco peR eceiving
R bT U
P C
PA
C CB BO
W P
350 m
350 m
C lassical C hannel
A lice
M. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Problems in Daylight• Destruction of detectors• Non-linearity of the detector
–Saturation
• Accidental clicks–Confused with real coincidence events
(QBER)
• Fluctuations of ~30dB (day/night)
0 2 4 6 8 100.0
0.5
1.0
1.5
2.0
2.5
Ideal Counts [10 cps]6
Det
ecte
d C
ount
s [1
0cp
s]6
M. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Expected Rates at daylight
M. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Sun & Solutions
blacko utco ating
fo cusing
sh ield
fo cusinginter ferencefilter
baffles pinho leto detecto r s
sun
- 3-4 dB-12 dB100µradFOV=10cmDt=1ns
M. Peloso et al., New J. Phys. 11 045007 (2009)
6.7nm
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
SetupAlice
BobM. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Measured rates at daylight
M. Peloso et al., New J. Phys. 11 045007 (2009)
• Sync possible at daylight
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Experimental results
coincidences(cps)
accidentalcoincidencerate ra (cps)
QBER (%)
raw key rate(s-1) key rate after
error correction (s-1)
total detection rateat receiver (kcps)
total 'local' detectorrate at source (kcps)
M. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
Conclusions• Entanglement based QKD in daylight, 4 days run without interruption• Synchronization works at ambient
conditions• Noise Suppression
–Spectral–Temporal–Spatial
• Brighter Sources…70 pairs/(s mW MHz)
M. Peloso et al., New J. Phys. 11 045007 (2009)
Ilja Gerhardt
QUANTUM OPTICSCQTGROUP
http://qolah.org
Thanks for your attention