Low cost, short range, free space quantum key distribution.

David Lowndes, Richard W R Nock, Stefan Frick, John Rarity

Research output: Contribution to conferenceConference Abstract


We present a Quantum Key Distribution system comprising a hand held transmitter device (Alice) and a

fixed terminal (Bob). The devices are highly asymmetrical with as much functionality as possible placed

into the Bob terminal (a 4u 19in. rack) which is much less restricted on its size. The small size

(80x50x10mm) and relatively low complexity will allow the hand held Alice to be cheaply mass produced

and therefore widely available.

A potential use for this technology would be as a method to allow the general public to benefit from a

wider metropolitan or national QKD network by establishing key with trusted network nodes.

The Alice device optics comprise 4 pulsed 300um LEDs behind polarizers to produce the photon states

for the BB84 protocol. Light from the LEDs is combined and spatially filtered using a single mode fibre,

the output of which is collimated by a lens at the optical output of the device. The device is currently

controlled via USB by a PC or mobile phone.

The Bob terminal is split into two modules; broadly categorized as “optical” and “processing”. The optical

module contains beam splitters for state discrimination and photon detection. The processing module

contains a PC, wireless router, time-tagging electronics and power supply. The modular approach allows

for a flexible platform for different QKD experiments, for example change of wavelength or protocol

would involve switching out only the optical module.

This work forms part of the Quantum Communications hub and was carried out with EPSRC funding

(Quantum Communications Hub, grant no. EP/M013472/1).
Original languageEnglish
Publication statusAccepted/In press - 2016
EventPhoton 16 - University of Leeds, Leeds, United Kingdom
Duration: 5 Sep 20168 Sep 2016


ConferencePhoton 16
CountryUnited Kingdom

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