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Quantum Communications attelecom wavelengths

Nicolas Gisin Hugo ZbindenToni Acin, Claudio Bareiro, Sylvain Fasel, J.-D. Gautier, Ivan Marcikic, Hugues de Riedmatten, Valerio Scarani,

André Stefanov, Damien Stucki, Sébastien Tanzilli, Robert Thew,

Wolfgang Tittel, GAP-Optique, University of Geneva

Q crypto over 67 km

Time-bins: high dimensions robustness of non-maximally entangled qubits Q teleportation at telecom

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The plug&play setup

D A P B S

L a se r

F R A P DA P D

A P DA P DPM

PM

Perfect interference (V99%) without any adjustments, since:• both pulses travel the same path in inverse order• both pulses have exactly the same polarisation thanks to FM

AliceBob

Drawback 1:Rayleigh backscattering

Drawback 2:Trojan horse attacks

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QC over 67 km, QBER 5%

+ aerial cable (in Ste Croix, Jura) !

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Company established in 2001– Spin-off from the University of Geneva

Products– Quantum Cryptography

(optical fiber system)– Quantum Random Number Generator– Single-photon detector module (1.3 m and

1.55 m)

Contact informationemail: info@idquantique.com

web: http://www.idquantique.com

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The qubit sphere and the time-bin qubit

qubit :

different properties : spin,

polarization, time-bins

any qubit state can be created

and measured in any basis

variable coupler variable coupler

1 0

h

Alice Bob

D0

D1

switchswitch

0

1

2

10

2

10

2

1i0

2

1i0

1

0

1010

iecc

1010

iecc

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entangled time-bin qubits

variable coupler

B

non-linearcrystal

0A

01

B

1A

depending on coupling ratio and phase , maximally and non-

maximally entangled states can be created

BA

i

BAecc 1100

10

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Arbitrary high dimensions

Net visibility = 91 % ±6 %

Entanglement for a two-photon state of dimension at least :

111

1

VD

Quant-ph/0204165; QIC 2002

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Partially Entangled Time-Bin Qubits

1100 10piecc

102 ccV

212

21

202

20 loglog ccccE

R.T.Thew et al. quant-ph/0203067

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Creation of a photon

Creation of a qubit

Creation of an entangled pair

The Bell measurement

teleportation setup

Creation of any qubit to be teleported

Analysis of the teleportedqubit

&

Coincidence electronics

3-fold 4-fold

F e m to -se c o n d la s e r

P u ls e w id th = 1 5 0 fs

M o d e lo c k e d T i :S a p h ire

L B O

R G filte rW D M

R G filte rW D M

G eA B

In G a A s C

L B O

B eam sp litte r 5 0 :5 0

In G a A s

I. Marcikic et al., quant-ph/0205144

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Bell measurement

BABABBAAii 0110101010

21

BABABBAAii 0110101001

21

)1010(01102121 BBAA

i BABA

011001102121

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Teleportation of a time-bin qubitequatorial states

2 photons +laser clock (1310&1550nm) 3 photons+laser clock

Raw visibility :Vraw=56 ± 5 %

Fidelity for equatorial states :

2

1 raweq

VF

=78 ± 3 %

Net visibility :Vnet=83 %±8%

0 5 10 15 20 25 30 35 40

0

10

20

30

40

50

Noise level

4-f

old

co

inci

de

nce

s [/

50

0s]

phase [a.u]

0

2000

4000

6000

8000

10000

12000

14000

3-f

old

co

inci

den

ces

[/5

00

s]

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Teleportation of a time-bin qubitNorth&South poles

1,00,1

0,11.0

PP

PF

%4%881,0 F

%4%840,1 F

0 1 2 3 4 5 6

0

50

100

150

200

250

300Time-bin 1Time-bin 0

Initial qubit

prepared in :

time-bin0

time-bin1

coin

cid

en

ces

[a.u

]

delay between start&stop [ns]

peqtot FFF3

1

3

280.5 % ± 3 %

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Long distance quantum teleportation

• Teleported qubit analyzed after 2 km of optical fiber and 55 m of physical distance (separate labs)

F e m to - se c o n d la s e r

P u ls e w id th = 1 5 0 fs

M o d e lo c k e d T i :S a p h ire

L B O

R G filte rW D M

R G filte rW D M

G eA B

In G a A sC

L B O

B eam sp litte r 5 0 :5 0

In G a A s

&

5 5 m

2 k m o f o p t ic a l f ib e r

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0 2 4 6 8 10 12 14 16 18 20-5

0

5

10

15

20

25

30

35

4-fold

4-f

old

[/5

00

s]

phase [a.u]

-2000

0

2000

4000

6000

8000

10000

3-fold

3-f

old

[/5

00

s]

Results for long distance teleportation

North & south poles

Fidelity for north&south poles :

1,0F

0,1F

= 88 ± 3%

= 77 ± 3%

0 1 2 3 4 5 6

0.0

0.2

0.4

0.6

0.8

1.0

1.2 Time-Bin 1Time-Bin 0Initial qubit

prepared in

time-bin 0

time bin 1co

inci

den

ces

[a.u

]

delay between start and stop [ns]

peqtot FFF3

1

3

281.2 % ± 2.5 %

Fidelity for Q teleportation over 2km

2

1 raweq

VF

= 80.5 ± 2.5 %

Equatorial states Raw visibility :Vraw=61 ± 5 %

Fidelity for equatorial states :

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Quantum teleportation as Q repeater (even without Q memory)

At telecom , the QBER is dominated by detector noise:

tC

2tC

4tC

tDQ 1

221

12221

tηDηtηt

DηtηtDηtQ

44

41

41

1 tDttQ

Alice Bobt

, D

Alice Bob, D

t t

, D

Alice Bob, D

41

t

, DBell

41

t 41

t 41

t

, D2 2 = 0.1 det. efficiency;

D = 10 dark count;

= 0.25 dB/km attenuation

-4

-100

-80

-60

-40

-20

0

0 25 50 75 100 125 150 175 200

Distance [km]

10 L

og

(r)

N. Gisin et al., Rev.Mod.Phys. 74, 145-195, 2002

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Conclusion

qubits and entangled qubits can be realized using time-bins.

entangled qudits in arbitrary high dimension d can be

realized.

partially entangled qubits are robust over 11 km.

Q teleportation

with:

telecom wavelength

two different crystals (spatially separated sources)

from one wavelength (1300 nm) to another (1550 nm)

first time with time-bins (ie insensitive to polarization fluctuations)

over 2 km of fiber and 55 meters of physical distance

mean fidelity : 81% both in the lab and at a distance

= the possibility to teleport the "ultimate structure" of an object from one place to another, without the object ever being anywhere in between