Quantum Communications in space using satellites...beam splitter (BS) I Two large ares SPADs mounted...

Quantum Communications in spaceusing satellites

Giuseppe Vallone, D. Bacco, D. Dequal, S. Gaiarin, M.Schiavon, M. Tomasin, V. Luceri, G. Bianco and P. Villoresi

"Fundamental and Quantum Physics with Lasers" WorkshopLNF - Frascati, 23 October 2014

Intro QC Results QKD Perspectives Conclusions

Summary

1 Introduction and motivations

2 Quantum communication in space

3 Results

4 QKD scheme

5 Perspectives

6 Conclusions

Pag. 2


Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions

Pag. 3


What is Quantum Communication?

I Quantum Communications is theability of faithful transmit quantumstates between two distant locations

I Ground QC have progressed up tocommercial stage using fiber-cables

I Quantum Communications onplanetary scale requirecomplementary channels includingground and satellite links

Pag. 4


Motivation

Why free-space quantum communications?

I Creation of a worldwide quantum

network: overcome fiber-losslimitations

IExplore the limits of Quantum

Mechanics and quantumcorrelations over very longdistances

Pag. 5


Context

I On May 24, 2014 Japan’s NICT launched SOTA onSocrates satellite.

I Ongoing programs for QC on satellite in China andCanada as well as in Singapore and USA.

Pag. 6


Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions

Pag. 7


Timeline

UniPD Space QComms University of Padova operated at Matera Laser Ranging Observatory, owned by the Italian Space Agency and directed by Dr. Giuseppe “Pippo” Bianco.

P. Villoresi et al. New J. Phys. 10 033038 (2008)

Pag. 8


Objectives

I To simulate a quantum source inSpace using orbiting retroreflectors

I To demonstrate the measurementof quantum states in the downlink

I To address the mitigation of thebackground noise

I To demonstrate quantumcommunication of a generic qubitsfrom Space to ground

I To envisage the exploitation of thistype of link

Pag. 9


MLRO facility

Matera Laser Ranging Observatory (MLRO):1.5 m telescope with millimeter resolution in SLR

research hub for Space QC since 2003

Dome Laser

Pag. 10


The making of the qubits

I Source on satellite simulated by a CCR

I Source (Alice) need to be at the singlephoton level

I Downlink attenuation from ⇠ 3 cm LEOsources in the range of 55-70 dB.

I Short pulses necessary for backgroundrejection

I Not too short to prevent bandwidthopening and noise increasing

CCR:Corner-CubeRetroreflector

Pag. 11


The making of the qubits

I MLRO master laser provided the solution:100 MHz, 100 ps, 300 mW, 1064 nm

I Second harmonics needed for qubits

I First order (6.2 µm) PPLN

I MgO doped Congruent Lithium Niobate -50 mm – thermally stabilized.

Pag. 12


Setup

Pag. 13 G. Vallone et al., Experimental Satellite Quantum Communications, [arXiv:1406.4051]


Coudé path of in-and-out

I Characterization ofthe polarizationtransformation

I Assessment oftotal transmissionefficiency

I Mutual alignementof SLR and Qubitbeams



Measuring the qubits

I The Coudé path is used in bothdirections for both the SLR beamand the qubits

I The upward and inward beams arecombined using a non polarizingbeam splitter (BS)

I Two large ares SPADs mounted tothe exit ports, designed to addressthe velocity-aberration

I 81 ps timetagging of 8 channels



Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions



Single passage of LARETS

Orbit height 690 km - spherical brass body24 cm in diameter, 23 kg mass,60 Metallic coated Corner-Cube Retroreflectors

Apr 10th, 2014, start 4:40 am CEST

0 50 100 150 200 250 300

1,000

1,200

1,400

1,600

−2 −1 0 1 2

20

10

0

10

20

−2 −1 0 1 2

−2 −1 0 1 2

−2 −1 0 1 2

∆=t meas

−t ref

(ns)

Time (s)

Co

un

tsS

ate

llite

dis

tan

ce (

km)

Det|H ⟩

Det|V ⟩

Det|H ⟩

Det|V ⟩

Det |L⟩

Det|R ⟩

Det|L⟩

Det|R ⟩

|H ⟩

|V ⟩

|L⟩

|R⟩

Detection of four polarization states received from satellite10 s windows: arrival time within 0.5ns from predictions



Link Budget and photon return rate

Radar equation for the prediction ofdetected number of photons per pulse

UPLINK

µsat

= µtx

⌘tx

G

t

⇢Aeff ⌃

✓1

4⇡R

2

◆T

a

DOWNLINK

µrx

= µsat

⌃

⇢Aeff

✓1

4⇡R

2

◆T

a

A

t

⌘rx

⌘det

Radar equation model provides a precisefit for the measured counts and the µ

sat

value for the different satellitesF

req

ue

ncy

(H

z)

1,600 2,100 2,60010

1

102

103

104

105

Ajisai

1,600 2,100 2,60010

1

102

103

104

105

Jason−2

1,000 1,400 1,80010

1

102

103

104

105

Larets

Satellite distance (km)

1,000 1,400 1,80010

1

102

103

104

105

StarletteStella



QBER: Quantum Bit Error Rate

Ajisai

Non polarization maintaining CCR:Polarization Q-Comm not possible

Jason-2, Larets, Starlette, Stella

Polarization maintaining CCR:I QBER compatible with applicationsI Demonstration of stable QBER over

extended link duration

0

50

100 Qd=39.2±0.8%Qn=39.2±0.8%

µ=3,432±42f̄=(1,964±24)Hz

Ajisai

0

10

20

30 Qd=6.0±1.4%Qn=1.8±0.1%

µ=1.8±0.1f̄=(100±6)Hz

Jason−2

0

10

20

30 Qd=1.2±0.1% µ=4.4±0.5f̄=(112±13)Hz

Qu

an

tum

Bit

Err

or

Ra

te (

%)

Larets

0

10

20

30 Qd=4.3±1.2%Qn=3.4±1.0%

µ=2.6±0.2f̄=(346±21)Hz

Starlette

0 10 20 300

10

20

30 Qd=6.8±2.3%Qn=5.0±1.9%

µ=1.3±0.1f̄=(149±15)Hz

Elapsed time (s)

Stella



Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions



QKD: quantum key distribution

I A novel approach towards unconditionally securecommunications

I Exploit quantum mechanics laws for establishing securekeys

I Single photon transmission for create keys and classicalchannel for send encrypted message



New QKD satellite protocol using retroreflectors

On the base of this experiment, we propose a two-way QKDprotocol for space channels:

I In the ground station, a linearly polarized train of pulses

is injected in the Coudé pathI The beam is directed toward a satellite with CCRs having

a Faraday Rotator (or equivalent), that rotate the returningpolarization by ✓, according to QKD protocol

I A measure of the intensity of the incoming beam avoidTrojan horse attack

I In the CCR a suitable attenuator lowers the mean photonnumber to the single photon level

I The state measure is done as in present experiment






is injected in the Coudé path

I The beam is directed toward a satellite with CCRs having










is injected in the Coudé pathI The beam is directed toward a satellite with CCRs having








The two-way QKD protocol:

I By this scheme, a decoy state BB84 protocol can berealised between satellite and ground

I Such protocol is currently realizable using few centimeterretroreflector as optical part in orbit



Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions

Pag. 24


Long term opportunities

Unique opportunity of Quantum Physics in SpacePossibility of testing quantum physics in new environment and

probing the laws of nature at very large distance

I Distribution of entanglement from Earth to Space

I Test of Bell’s Inequalities with unprecedented conditions:LEO or GEO-orbit, moving terminals, gravitational field

I Teleportation from Earth to Space

I Quantum technologies in long distance applications

I Test of foundations of quantum field theory and generalrelativity

Pag. 25


Entanglement distribution

I Quantum Entanglement is, according toErwin Schrodinger, the “characteristic traitof quantum mechanics”

I Entanglement is a unique resource forQuantum Information applications(teleportation, dense coding, etc..)

| iAB

6= |�iA

⌦ |�iB

A

B

| iAB

I Limits on the distance between two entangled systems?I Is entanglement limited to certain mass and length scales

or altered under specific gravitational circumstances?

Pag. 26


Entanglement distribution

Photons are the ideal candidate for distributing entanglementI Easy to generate entangled photons

!"#$%&'

()*+,%

")*+,%

-,.&,/0%123+.+,4

I Photons can travel over long distances withoutdecoherence

Pag. 27


Bell’s test

If a set of correlation do not satisfy the Bell’s inequality S 2,the correlations cannot be explained by a local realistic theory.

I Bell’inequality violated between fixed location: "spookyaction at distance" at speed greater than 104

c.

I Bell’s test with moving terminals

Pag. 28


Bell’s test

If a set of correlation do not satisfy the Bell’s inequality S 2,the correlations cannot be explained by a local realistic theory.

I Bell’inequality violated between fixed location: "spookyaction at distance" at speed greater than 104

c.

I Bell’s test with moving terminals1

1x 2y

2

2

1

t

Test of Test ofS S

t

z

z

Pag. 28


Summary



3 Results

4 QKD scheme

5 Perspectives

6 Conclusions

Pag. 29


Conclusions

I We have experimentally demonstrated QuantumCommunication from several satellites acting as quantumtransmitter and with MLRO as the receiver

I QBER was found low enough to demonstrate the feasibilityof quantum information protocols such as QKD along aSpace channel

I The ability of propagating quantum correlation over largedistance will have a great impact for fundamental physicsand quantum information applications

Pag. 30


REFERENCES

I G. Vallone, D. Bacco, D. Dequal, S. Gaiarin, V. Luceri, G. Bianco, P.Villoresi, Experimental Satellite Quantum Communications,[arXiv:1406.4051]

I P. Villoresi, et al., Experimental verification of the feasibility of a

quantum channel between space and Earth, New J. Phys. 10, 033038

(2008)

I C. Bonato, et al., Feasibility of satellite quantum key distribution, New J.

Phys. 11, 045017 (2009)

I A. Tomaello, et al., P. Link budget and background noise for satellite

quantum key distribution Adv. Sp. Res. 47, 802 (2011)

I D. Rideout, et al., Fundamental quantum optics experiments

conceivable with satellites reaching relativistic distances and velocities

Class. Quantum Gravity 29, 224011 (2012)

Pag. 31

Quantum Communications in space using satellites...beam splitter (BS) I Two large ares SPADs mounted...

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