National Network of Quantum Technologies Hubs:

Quantum Communications Hub

Director: Professor Tim SpillerAffiliation

Quantum Communications Hub: Partners

Academic partners:York (lead), Bristol, Cambridge, Heriot-Watt, Leeds, Royal Holloway, Sheffield, Strathclyde

Industrial partners:R&D: Toshiba Research Europe Ltd. (TREL), BT and the National Physical Laboratory (NPL)

Network: ADVA, NDFIS

Supplier/Consultancy (optical): Oclaro, ID Quantique

Collaboration/Consultancy (microwave): Airbus, L3-TRL

Start-ups (exploitation): Qumet (Bristol), Cryptographiq (Leeds/IP Group)

Standards/Consultancy: ETSI, GCHQ

User engagement: Bristol City Council, Knowle West Media Centre, Cambridge Science Park, Cambridge Network Ltd

Quantum Communications Hub

Vision:

“To develop new quantum communications (QComm) technologies that will reach new markets, enabling widespread use and adoption in many scenarios – from government and commercial transactions through to consumers and the home.”

Delivery:

First generation: Take proven concepts in Quantum Key Distribution (QKD) and advance these to commercial-ready stages. (Work packages 1-3)

Next generation: Explore new approaches, applications, protocols and services – beyond QKD. (Work package 4)

Quantum Key Distribution (QKD)

Secure sharing of a key between two parties (Alice and Bob!)

The quantum part is the distribution of the key, with a promise from quantum physics that only Alice and Bob have copies.

Once distributed, the (non-quantum) uses of the key(s) cover a wide range of secure information tasks: communication or data encryption, financial transactions, entry, passwords, ID/passports…

The keys are consumables (use once only for security), so need regular replenishment, which is “quantum”.

Quantum Communications Hub: Work packages

WP1 Short Range Consumer QKD (WP Lead: John Rarity (Bristol))Near infra red, line-of sight

Microwave

WP2 Chip Scale QKD Components (WP Lead: Mark Thompson (Bristol))Chip scale optics

Network switches

WP3 Quantum Networks (WP Lead: Andrew Shields (TREL))Quantum Core Networks

Quantum Metro Networks

Quantum Access Networks

WP4 Next Generation QComm (WP Lead: Gerald Buller (Heriot-Watt))Quantum digital signatures

Quantum Relays, Repeaters and Amplifiers

Device Independent and Measurement-device independent QKD

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Quantum Communications Hub: Work packages

WP1: Quantum secured key exchange for consumers

Could use one-time-pad to protect the PINGenerate one-time-pad using quantum secured key exchangeKey exchange at ATM allows user to ‘top-up’ a personal one-time-pad.

<€3000

<€10

WP1: Why?• Weekly ‘top-up’ a personal one-time-

pad into a personal phone/card.• Protects against ‘skimming’• Type your PIN into YOUR device• Absolute security for PIN online • Low cost: free to all customers

The competition:• present readers provide simplistic

security based on ‘toy’ codes. • In shops: data between card and

reader NOT encrypted during a transaction, PIN is sent in the clear!

See http://www.cl.cam.ac.uk/~sd410/See also google/vodafone: phone=wallet

Hacking demo

9

Bob meets Alice

WP1: The credit card Alice

New System: Target 3x20x40mm Alice>100MHz operation

WP1: Flexible receiver and software concept:

Standard 19” rack system with replaceable receiver and software sub-units

WP2 Vision: Chip-based Qcomms devices

Current approach

Integrated quantum photonicQcomms chip

1mm

• Chip-based devices for:• Low cost• Compact• Energy efficient• Mass-manufacture• Compatibility with current microelectronic devices

• Hub will target:• Fully integrated and packaged QKD devices with control electronics • Deployment in real networking situations

WP2: Compact chip-based QKD

WP2: Targeted Applications

• Mobile devices• Computer networks• City wide communications

network

WP2: Chip-based QKD/WDM switches

• Compact switching device for reconfigurable quantum networks

• InGaAsP devices based on Clos switching architecture

4x4 building block 16x16 integrated

switch

Today: Point-to-point fibre QKD links

WP3: Quantum Networks

Explore integration of QKD in different network segments (long-haul, metro, access)

Multiplex quantum signals on conventional DWDM grid

Provisioning of quantum and data channels

Key management and security analysis of extended trusted node network

Application development, eg layer 3 encryption, quantum digital signatures

WP3: Quantum Networks

DWDM DWDM

quantum

data

... ...

Metro AccessLong-Haul

Establish large-scale Quantum Network test-bed in UK

Implemented in stages

Metro networks in Cambridge and Bristol

Long-haul network connecting Cambridge-London-Bristol (NDFIS) with possibility to extend

Access networks providing multi-user connectivity

A focus for application development, industrial standardisation and user engagement

NPL

Cambridge

BristolUCL

Telehouse

Southampton

Reading

Martlesham(BT)

TREL

Potential test-bed for the other QT Hubs and associated projects

WP3: UK Quantum Network

WP 4: Emerging Quantum Communications TechnologiesQuantum Digital SignaturesInformation Theoretic Secure Digital Signatures

Quantum RepeatersAmplifiers for Quantum Communications Systems

Measurement Device Independent Quantum Key DistributionCryptographic Key Exchange in an Untrustworthy World

�̂�

�̂�

Noiseless amplifier

Quantum limited amplifier

Classicalamplifier

Coherent states

Alice

Charlie

Bob

|ΨAlice>

|ΨAlice>

Verify

Alice

BobUntrusted

Measurement Unit

Several km

Several km

Quantum Comms Hub: Theory and Security Analysis

Contributes to all four Technology Workpackages:Identify and remove security vulnerabilities at an early stage

Contribute to ETSI standards for QKD and other Qcomm systems

Physical level security analysisMatch physical models for analysis to practical implementations

Widely applicable channel analysis with side channel information leakage studies

Analysis of attacks and countermeasure design

Protocol level security analysisAnalysis of protocol stacks, incorporating low-level quantum and higher level conventional protocols

Analysis of practical security advantages of new protocols such as QDS and MDIQKD

“Quantum-immune” conventional (classical) protocols

Hybrid system analysisHigh speed (Gb/s upwards) systems combine QKD and conventional secure communications protocols, trading unconditional and forward security for speed

Detailed security analysis of such hybrid systems (and mitigation against security “loss”) is needed

Quantum Communications Hub: Work package targets“Commercial-ready” QKD technologies...

WP1 Short Range Consumer QKD Handheld system, leading to minimal mobile phone modification for Alice

Microwave quantum secure communications analysed and demonstrated

WP2 Chip Scale QKD Components Chip scale Alice with semi-bulk Bob, leading to fully packaged chip scale QKD optical modules

Network switches demonstrated on the UKQN

WP3 Quantum NetworksHigh bit rate link encryption

Quantum Metro Networks demonstrated in Bristol and Cambridge

Establishment and operation of the UKQN

WP4 Next Generation Quantum CommunicationsQuantum digital signatures deployed at Metro Network level

Quantum Relays/Repeaters for weak pulse QKD demonstrated on UKQN

Device Independent and Measurement-device independent QKD deployed at QAN level

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National Network of Quantum Technologies Hubs:

Quantum Communications Hub

Director: Tim Spiller

Main partners: York (lead), Bristol, Cambridge, Heriot-Watt, Leeds, Royal Holloway, Sheffield, Strathclyde, Toshiba Research Europe Ltd. (TREL), BT and the National Physical Laboratory (NPL)

The UK National Quantum Technologies Programme aims to ensure the successful transition of quantum technologies from laboratory to industry. The programme is delivered by EPSRC, Innovate UK, BIS, NPL, GCHQ, DSTL and the KTN.

QCrypto – Example Key Distribution

• Alice sends photons one by one, chosen at random from

• Bob chooses to measure polarization in basis or chosen at random.

• Bob announces publicly his list of bases used, but not his results! (Null results are identified and discarded.)

• Alice tells Bob which data to keep, those where he used the basis in which she transmitted.

• They agree a protocol for 0,1 in each basis to obtain a shared bit string, the raw quantum transmission (RQT).

Alice and Bob use alternative bases of individual photonic qubits(e.g. plane polarization) to keep Eve guessing (BB84 protocol).

| >| > | >| >

QCrypto – Example Key (BB84)

Alice …

Bob …

Keep? yes no yes yes no no yes no …

Bit 1 -- 0 0 -- -- 0 -- …

| > | > | > | > | > | >| > | >

| > = 0| > = 1 | > = 0 | > = 1

QCrypto – Eavesdropping

• Eve cannot clone qubits, but she can try the same as Bob --- guess a basis at random from or , measure the polarization and then send on a photon to Bob polarized as per her result.

• Out of the results which Alice and Bob keep, Eve will guess wrong (on average) half of the time. Out of these (through measurement in the wrong basis), Bob will (on average) project half of these photons back to the original state transmitted by Alice. Eve therefore corrupts 25% of the RQT which she intercepts.

• More involved eavesdropping strategies also leave evidence: the irreversibility of quantum measurement ensures that Eve cannot gain information without causing disturbance.

QCrypto – Errors and key distillation

• Using the public channel, A and B can: • - Estimate Eve’s activity • - Detect and eliminate errors in the RQT • - Distil a highly secure key• However, this costs! For every bit of information revealed

publicly, a component bit is discarded to avoid increasing Eve’s information.

-6

-6•e.g. 4% RQT errors: 2000 ---> 754 bits (Eve knows ~10 bit)• 8% RQT errors: 2000 ---> 105 bits (Eve knows ~10 bit)

WP4: MDI-QKD

Alice Bob

Measurement Unit

BS PBSPBS

D1

D2

D3

D4

Current QKD systems secure the fibre, but equipment must be physically secure

Measurement Device Independent (MDI) QKD relaxes the requirement to trust the detectors. (The detectors can even be operated by Eve)

Mitigates all attacks on the detectors.

We plan to demonstrate a practical and efficient system for MDI-QKD.

Complimented by theoretical analysis of MDI-QKD, as well as complete DI-QKD.

& several “hacks” on detectors demonstrated

Alice Bob

Eve’s domain

WP 4: Quantum Digital Signatures

• Authentication• A receiver believes the message was from a known sender.

• Non-repudiation • A sender cannot deny sending a message, without claiming that the private key has

been compromised.

• Integrity• The message was not altered in transit.

• Transferable• The message is transferrable: Bob can be sure that if he forwards the message to

Charlie, then Charlie will also accept the message as genuinely from Alice.

Alice

Charlie

Bob

|ΨAlice>

|ΨAlice>

WP 4: Quantum Digital Signatures

0

π

π/23π/2

Phase

Phase encoded coherent states:“A quantum one-way function”

Intensity

The lower the intensity, the harder it is to distinguish between the phases of the coherent states

Difficult Easy

Coherent

States

Classical List of

Phases

Set phases

Measure phases

Alice

Bob & Charlie

WP 4: Quantum Repeaters

Classical amplifier: Increases the amplitude of the signal

Quantum amplifier: A perfect amplifier would violate the

No-cloning Theorem

�̂�

�̂�

Noiseless amplifier

Quantum limited amplifier

Classicalamplifier

Coherent states

We pay the price in the form of noise:

Classical: noise is added from the technical

limitations of the equipment

Quantum: Heisenberg’s relation prevents exact

knowledge of the signal, i.e. intrinsic noise

Solution: Non-deterministic (or probabilistic) amplifier

– Keep the success probability low

Original Perfect

copy

Imperfect

copy

WP 4: Quantum Repeaters

|𝛼 ⟩ ⟨ 𝛼|

|𝛼 ⟩ ⟨ 𝛼|

𝑝1|√ 2𝛼 ⟩ ⟨ √2𝛼|+𝑝2|0 ⟩⟨ 0|

“0”

Detector|−𝛼 ⟩ ⟨−𝛼|

Detector

“1”

|𝑡 √2𝛼 ⟩ ⟨ 𝑡 √2𝛼|𝑡≈1

𝑝1>𝑝2

Sub

trac

tion

Com

paris

on

Vacuum 𝑟 ≈0

ImperfectIndication of Amplification

?

 

WP 4: Quantum Teleportation

RM Stevenson, J Nilsson, AJ Bennett, J Skiba-Szymanska, I Farrer, DA Ritchie, AJ Shields arXiv preprint arXiv:1307.3197

References for WP 4

• P J Clarke, R J Collins, V Dunjko, E Andersson, J Jeffers and G S Buller, Nature Comm. 3, 1174 (2012).

• V Dunjko, P Wallden and E Andersson, Phys. Rev. Lett. 112, 040502 (2014).

• E Eleftheriadou, S M Barnett and J Jeffers, Phys. Rev. Lett. 111, 213601 (2013).

• R J Donaldson et al., Experimental Implementation of a Quantum Optical State Comparison Amplifier, arxiv:1404.4277.

• C L Salter et al. An entangled-light-emitting diode, Nature 465, 594–597 (2010).

• M Stevenson et al.,Nature Comm. 4, 2859 (2013).