Quantum Communications with Cubesats

UNSW

10 July 2018

Rob Malaney UNSW

Image: Zeilinger 2000

Quantum Communications (Malaney, Globecom 2016)

QKD (revisited) – Product Status

ID Quantique.com

•Provide secured quantum keys for any encryption device

•Scalable: one quantum key server can distribute keys for up to 100Gbps of data

•Fully automated key exchange with continuous key renewal

•Integrated entropy source based on a •Quantum Random Number Generator

•Adaptable: Works on dark fibre and •WDM networks

~100km in Fibre Quantum Key Rate 1MB/s at 50km (Fibre)

Toshiba.com “Decoy” rate

IDQuantique, Toshiba, MagiQ, SeQureNet, QinetiQ, Quintessence (CV states)

4) Emerging Apps –QKD (revisited) (Malaney, Globecom 2016)

QKD (revisited) Status - Free Space

Lo et al 2014

a, First free-space demonstration of QKD19 realized two decades ago over a distance of 32 cm. The system uses a light-emitting diode (LED) in combination with Pockels cells to prepare and measure the different signal states. b, Entanglement-based QKD set-up connecting the two Canary Islands La Palma and Tenerife6. The optical link is 144 km long. OGS, optical ground station; GPS, Global Positioning System; PBS, polarizing beamsplitter; BS, beamsplitter; HWP, half-wave plate. c, Schematic of a decoy-state BB84 QKD experiment between ground and a hot-air balloon20.

4) Emerging Apps –QKD (revisited) (Malaney, Globecom 2016)

Large Scale Systems –

Towards the Quantum Internet Two Recent Important Network Results

Rob Malaney

Hefei, China

Sun et al 2016. Calgary, Canada

Valivarthi et al 2016.

4) Emerging Apps – The Quantum Internet (Malaney, Globecom 2016)

Why Quantum Communications via Space• Quantum Communications is the next Communication Frontier

• China has recently demonstrated all forms of Quantum Communication via satellite are feasible

• Long-range Quantum Communication via satellite will enable the Quantum Internet

• The Quantum Communication will provide for the most secure communication systems known – secured solely by the laws of physics

GEO ORBIT

GEO spacecraft Alphasat I-XL 38000km

Quantum-limited measurements of optical signalsfrom a geostationary satelliteGÜNTHNER e atl 2018

GPS ORBIT

GLONASS Reflector spacecraft 20000km

Towards Quantum Communication from Global Navigation Satellite SystemCalderaro et al 2018

MICIUS (China)

GLONASS Reflector spacecraft 20000km

Satellite-relayed intercontinental quantum networkSheng-Kai Liao et al 2018

QKD via Nano Satellite

DEMONSTRATING MINIATURISED, ENTANGLED PHOTON-PAIR SOURCES ON BOARD NANO SATELLITES TO ENABLE FUTURE QKD MISSIONS R. C.M.R.B. Chandrasekaraa 2018

Table 1 | Specifications of the SOTA and loss characteristics of the link and the OGS.

Tx2 Tx3 CommentsSpecifications of SOTAPolarization Linear Linear Ellipticity <0.1°Wavelength (μm) 0.8 0.8 At 25 °C, centre wavelength varies at 0.1 nm °C–1

Wavelength width (nm) 0.2 0.2 Measured at −3 dB full widthClock frequency (MHz) 10 or 1 10 or 1 SelectableIntensity (MWsr−1) 2.68 × 10−3 3.30 × 10−3 Average power at 10 MbpsMean photon number per pulse 2.34 × 108 1.78 × 108

Beam divergence (μrad) 970 880 Measured at −3 dB full widthPointing loss (dB) −1.5 −1.9 Owing to small misalignment of Tx2/3 from the direction

of pointing beam from Tx4Transmit aperture (mm) <5 <5SOTA optical loss (dB) −0.2 −0.2

Loss characteristics of the link and the receiver for a 53° elevation angleAtmospheric attenuation (dB) −3.55 −3.55 Estimated with the code MODTRAN (Spectral Sciences)Space coupling loss to the receiver telescope (dB) −57.8 −56.9 Evaluated for a SOCRATES–OGS distance

of 802 km at 22:59:00 JSTReceiver’s telescope loss (dB) −2.68 −2.68 −1 dB due to primary mirror and −1.68 dB due to secondary

and tertiary mirrorsQuantum receiver loss (dB) −14.5 −14.5 Evaluated by using star light (Supplementary Table 1)Total loss budget (dB) −78.5 −77.7

Primary mirror

Tertiarymirror

Secondarymirror

1 mtelescope

SOTA

SOCRATES

SPCM2SPCM1

SPCM3

SPCM4

Lens

Lens

LensLens

Lens

PD

IRtrackingcamera

BS

PBS

PBS

DM

Iris

Mirror

Mirror

Collimatinglens

×10 beamreducer

HWP45°

Lens

Filter

BS

Tx2/3 path(0.8 µm)

Tx4 path(1.5 µm)

Nasmythbench

d

z

x

y

SOTAa b

−44°

z

yx

Tx3

Tx2

Tx2 and Tx3

c

Figure 1 | Transmitter and receiver systems. a, Picture of the SOTA (18 cm width × 11 cm depth × 27 cm height). b, Configuration of the two linearlypolarized laser diodes Tx2 and Tx3 in the SOTA. c, Receiver telescope. d, Quantum receiver. DM; dichroic mirror; PD, photodetector; IR, infrared;BS, beamsplitter; PBS, polarizing beamsplitter; HWP, half-wave plate; SPCM, single-photon counter module. In the NICT OGS, incident light reflected by theprimary and secondary mirrors passes through a tertiary mirror (made of aluminium to minimize linear polarization deterioration). The beam after thetertiary mirror has a width of 3 mm and is guided towards the quantum receiver installed at the Nasmyth bench of the telescope. A 1.5-μm-wavelengthcircularly polarized beam from the SOTA was used for satellite tracking and was separated from the 0.8-μm-wavelength light using a dichroic mirror in thequantum receiver. This 1.5 μm beam was then guided to a PD and monitored using an IR camera. The quantum receiver consists of BSs, PBSs and a HWP,ending with four ports, where four SPCMs based on Si avalanche photodiodes were used as detectors after coupling the beams to multimode optical fibresusing converging lenses. Received photon counts were then time-tagged by a time-interval analyser (timing resolution of 1 ps), generating a time-taggedphoton-count sequence for each SPCM.

NATURE PHOTONICS DOI: 10.1038/NPHOTON.2017.107 ARTICLES

NATURE PHOTONICS | VOL 11 | AUGUST 2017 | www.nature.com/naturephotonics 503

© 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.

Conclusions

Quantum Communications is an exciting new area for engineers – it is here to stay. It will deliver the ultimate cyber-security solutions to next-generation networks. There are many real-world problems looking for real-world engineering solutions. Specific engineering challenges highlighted here include - Large-scale City-wide Networks Space-based Communications The Global Quantum Internet New Multiplexing Schemes (OAM) Next-Generation (6G) Wireless Communications

Nano Satellites Challenges – seem biggest

5) Conclusions (Malaney, Globecom 2016)