Quantum key distribution using quantum dot single-photon emitting
Differential-Phase-Shift Quantum Key Distribution Quantum Key Distribution Kyo Inoue Osaka...
Transcript of Differential-Phase-Shift Quantum Key Distribution Quantum Key Distribution Kyo Inoue Osaka...
Differential-Phase-Shift Quantum Key Distribution
Kyo InoueOsaka UniversityNTT Basic Research LaboratoriesJST CREST
Collaboration with
H. Takesue, T. Honjo (NTT Basic Res. Labs.)
Yamamoto group (Stanford Univ.)
(1)DPS-QKDSetup & ProtocolEavesdroppingExperiments
(2) Modified protocol with decoy pulses
(3) Entanglement-based schemes
(4) DPS-QKD using macroscopic coherent light
(5) DPS quantum secret sharing
Contents
T
. . . .att.
0.1-0.2 photon/pulseAlice
{0, π}
DET-1
DET-2
Bob
coherentpulsesource
phasemod.
T
DPS (Differential-Phase-Shift) QKD
. . . .. . . .
Δθ
= 0 DET-1
Δθ
= π DET-2
time
Protocol(1) Signal transmission(2) Bob Alice: photon detection time(3) Alice knows which detector clicked at Bob.(4) Key bits are created as
DET-1 = “0” DET-2 = “1”
Features・Simple configuration・Efficient usage of the time domain・No photon discarded・Robustness against photon number splitting attack
Alice
Eve. .. .Bob
error
Eavesdropping - intercept & resend -
Tran
smitt
er
0.1-0.2 photon/pls.
・A photon is detected once in 10 slots.
・She sends a photon over two pulses with measured phase difference.
・She sends nothing for unmeasured slots.
41
21
21
=×
Eavesdropping !
Eavesdropping - photon number splitting -
Bob
Eve
×
Alice
. .. .photon number measurement(QND)
split gatelossless
errorEavesdropping !
transmission loss (dB)
key
crea
tion
rate
(log
)
DPS
BB84 with laser
DPS-QKD Experiment
cw-laser intensitymod.
phasemod.
att.
pulsepatterngenerator
rep. rate:10 GHz
{0, π}
datagenerator
. . . .
timeintervalanalyzer
fiber
logicunit
waveguideinterferometer
SSPDlow noisenon-gatinglow jitter
Takesue et al., Nature Photon., 1, 343 (2007)collaborating with NIST
17 kbit/s at 100 km.12 bit/s at 200 km.
Secure key against general individual attackbased on Edo, Takesue, Yamamoto, PRA 73, 012344 (2006).
Result
QE=1.4 %d.c.=50 cps
SSPD
Field Transmission
NTT Yokosuka R&D Center
NTTYokosuka Office
17.8 km
PPLNphoton (1.55μm)
pump (0.98μm)
0.6μm
Si-APDfilter
delay (200ps)
PBSBS
Up-conversion photon detector
for polarization independency
pulse rate: 1 GHz
λ/2
QE: 2 %, d.c.: 2.8 kcps
0 100 200 3002
3
4
5
6
50000
100000
150000
QB
ER
(%
)
Time (min)
Sifted key generation rate (bps)
QBER 3.14% (Avr)
Rate 120.26kbps (Avr)
Result
Sifted key:120 kbit/s with a QBER of 3.14 %.
(1)DPS-QKDSetup & ProtocolEavesdroppingExperiments
(2) Modified protocol with decoy pulses
(3) Entanglement-based schemes
(4) DPS-QKD using macroscopic coherent light
(5) DPS quantum secret sharing
DPS-QKD with Decoy Pulses
. . . .
Bob
modified version
Eavesdropping is found by bit error rate
Alice BobEve bit erroreavesdropping !
Conventionally
Eve gets some key bits, utilizing system errors.
Alice
μ μ
10μ μ μ
. . . .
. . . .
μ 5.5μ
5.5μ μ
Bob
Eve
Trans.
Intercept & Resend attack is prohibited.
decoy click
Intercept & Resend against DPS-QKD with Decoy
Eavesdropping !
. . . .
. . . .
. . . .
Alice
1 : 2 : 1count rate:
Eve does not know whether a click is decoy or not.
distance (km)
key
crea
tion
rate
(/pu
lse)
Simulation
0 20 40 60 80 100 120
10-1
10-2
10-3
10-4
10-5
10-6
10-7
decoy DPS
conventional DPS suffering from general individual attack
fiber loss: 0.25 dB/kmdark count: 10-5/gatedetection efficiency: 0.120% fluctuates in detection rate.
Transmission length can be extended.
(1)DPS-QKDSetup & ProtocolEavesdroppingExperiments
(2) Modified protocol with decoy pulses
(3) Entanglement-based schemes
(4) DPS-QKD using macroscopic coherent light
(5) DPS quantum secret sharing
. . . .< 1 photon/pls.
BobAlice
signal idler
pumppulse source
・ ・・ ・
< 1 photon/pls.
DPS-QKD utilizing Entanglement
. . . .
. . . .
. . . .. . . .
. . . .
parametricmedium
correlation
secret key
Entanglement generation
future scheme for long distance
Quantum Relaying DPS-QKD
・・ ・・ ・・ ・・
Entanglementgeneration
Entanglementgeneration
signal 1 idler 1・・ ・・
signal 2・・ ・・
idler 2Alice Bob
Charlie
Experiment: Entanglement Transmission
DSF(50km)
frequencyup-conversiondetector
LD1551nm
IM EDFA FBG
waveguideinterferometer
Frequencyup-conversiondetector
1 GHz 100 ps
PPLN (SHG)
Filter
1.5μmsuppression
PPLN(parametric down conversion)
Filter
Filter
1555nm1547nm
pump (0.7-μm)Suppression
1547,1555nmseparation
DSF(50km)
waveguideinterferometer
timeintervalanalyzer
QE: 4.4 1.4 %d.c.: 4kcps
24.0 24.50
5e−05
0.0001
0
5000
10000
15000
PLC temperature for idler (deg.)
Coi
ncid
ence
rat
e pe
r si
gnal
cou
nt
Count rate for idler (H
z)
Visibility of 81.6% without removing background noise.
Average number of photon pair: 0.07/pilse.
Time-bin entangled photons are successfully transmitted over 50 x 2 km.
Result
two-photon interference data on TIA
waveguide temperature for idler (deg)
(1)DPS-QKDSetup & ProtocolEavesdroppingExperiments
(2) Modified protocol with decoy pulses
(3) Entanglement-based schemes
(4) DPS-QKD using macroscopic coherent light
(5) DPS quantum secret sharing
BobAlice
{-δ, δ}dec.
δ Re[E]
Im[E]
θ4
θ3
θ2
θ1
θi = {δ, –δ}
θ4
θ3
θ2
θ1
θ4
θ3
θ2
θ1
Coherentsource
Δθ
= {δ, 0, –δ}
Phasemod.
DPS-QKD using Macroscopic Coherent Light
quantum noise
signal level, I
Prob
abili
ty
Conventionally, photon counting is needed.
(1) Alice → Bob:Signal transmission
Secret key
Protocol
(2) Bob creates bit “1” when I > Id
bit “0” when I < - Id
(3) Bob → Alice:Time slot at which bit was created
(4) Alice creates bit “1” in case θi – θi+1 = 2δbit “0” in case θi – θi+1 = – 2δ
for the time slot at which Bob created bit.
(5) Alice → Bob:Time slots for which θi – θi+1 = 0
(6) Bob discards the bits for θi – θi+1 = 0
“0” “1”
Id-Id
Conventional photodetectors are available.
Fiber length (km)
Key
cre
atio
n ra
te (/
slot
)
BE
EBk
ββ
αα
≡
α:detection efficiency
β:noise factor
k is a parameter indicating performance of Bob’s detectorrelative to Eve’s.
Simulation (1)
0 10 20 30 40 50
1
10-1
10-2
10-3
10-4
10-5
k = 1
k = 0.5
k = 0.25
Final key creation rate: Rs (IAB – max{IAE , IBE })
Rs : sifted key rateIAB : mutual information between Alice & BobIAE : mutual information between Alice & EveIBE : mutual information between Bob & Eve
Alice
error correction
Bob
Simulation (2)
0 50 100 150 200
fiber length (km)
1
10-1
10-2
10-3
10-4
10-5
key
crea
tion
rate
(/sl
ot)
k = 1
k = 0.5
k = 0.25
Final key creation rate: Rs (IAB – IBE )
Alice
error correction
Bob
(1)DPS-QKDSetup & ProtocolEavesdroppingExperiments
(2) Modified protocol with decoy pulses
(3) Entanglement-based schemes
(4) DPS-QKD using macroscopic coherent light
(5) DPS quantum secret sharing
Quantum Secret Sharing (QSS)Function
Alice and Bob have fractions of a secret key shared with Charlie.Alice (or Bob) cannot decipher message from Charlie by her (or him) alone.
Previous scheme
Alicesecrete key
partial key partial key
secrete key Bob
Charlie
- Entanglement based scheme- BB84 based scheme
・ ・・ ・ ・ ・・ ・
phasemod.{0, π}
coherentpulsesource
phasemod.
monitor
~ 1ph./plsatt.
Alice CharlieBob
ΔθaΔθb “0”
“1”
0 π0 “0” “1”π
“1” “0”
Δθa
Δθb
{0, π}
DPS Quantum Secret Sharing (QSS)
Charlie’s data are XOR of Alice’s and Bob’s.
・ ・・ ・
・ ・・ ・
Charlie’s data are recovered in collaboration of Alice and Bob. QSS
Eavesdropping by dishonest Bob
Eavesdropping by dishonest Alice
phasemod. Charlie
Bob
coherentpulsesource
Bob cannot fully know Alice’s data.
measure
phase mod. Charlie
Bob Alice
Alice
Eavesdropping against DPS-QSS
Alice ~ 0.1 photon/pls.
~ 0.1 photon/pls. coherentpulsesource
measurephasemod.
Alice cannot fully know Bob’s data.
Bob’s monitoring forces Alice to send 0.1 ph/pls.
fiber(5km)
fiber(5km)
rep: 1 GHzpulse width: 125 ps
0.1 ph./pls
waveguide interferometer
ΔL = 20 cm
1 Gbps 1 Gbps
10:1 coupler
APD
APD(4MHz)
QBER: 6.4 %sifted key rate: 3.9 kbps
Experiment
cw-laser intensitymod.
pulsepatterngenerator
datagenerator
phasemod.
datagenerator
phasemod.
timeintervalanalyzer
att.
error correctionprivacy amplification final key rate: 1.5 kbps
Summary
(3) Entanglement-based schemesExperiment utilizing fiber four-wave mixing for entanglement generation.
DPS-QKD is presented.
(1) Setup & protocol, eavesdropping, experimentsSimple configuration, no photon discarded.Robust against photon-number-splitting attack12 bit/s at 200 km, 17 kbit/s at 100 km for secure key (with SSPD)
(2) Modified protocol with decoy slotsIntercept-resend attack is prohibited.
(4) DPS-QKD using macroscopic coherent lightConventional photodetectors are available.
(5) DPS quantum secret sharingSimple configuration