We review our low cost and short range quantum cryptography system designed to exchange keys between a hand-held device and a fixed terminal such as an ATM. Performance metrics and use scenarios will be described.
A Quantum Key Distribution system has been demonstrated with a focus on applicability of the technology to a consumer use model.The optical devices were split into a large, expensive "Quantum ATM" (the Bob terminal) and a small, cheap handheld section (the Alice device).Work was initially done to integrate the devices into a realistic demonstration system which was exhibited at several international conferences.Following this success, the devices constituent parts were isolated and improved upon.Work on the Alice device focused upon proposing a new scheme for light collimation and then investigating a method to enact this.In the Bob device the progress was directed towards a more effective single photon detection system utilizing active quenching.An asymptotic secure key rate of 20kb/s was obtained at a bit error rate (BER) of 4% corresponding to a daylight operation scenario.A docking scheme was enacted to simplify the alignment of the optical channel which was shown to be repeatable over at least 50 cycles.The system was also shown to be stable over an extended period of time.
Abstract We present a miniaturized quantum key distribution system, designed to augment the more mature quantum key distribution systems currently commercially available. Our device is designed for the consumer market, and so size, weight and power are more important than raw performance. To achieve our form factor, the transmitter is handheld and the receiver is a larger fixed terminal. We envisage users would bring their transmitters to centrally located receivers and exchange keys which they could use at a later point. Transmitting qubits at 80 MHz, the peak key rate is in excess of 20 kbps. The transmitter device fits within an envelope of <150 ml, weighs 65 g and consumes 3.15 W of power.
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).