Modulator‐Free Coherent‐One‐Way Quantum Key Distribution

Z L Yuan,M Lucamarini,G L Roberts,A J Shields,S J Savory,J F Dynes

doi:10.1002/lpor.201700067

Z L Yuan, M Lucamarini + Show 4 more

Open Access

https://doi.org/10.1002/lpor.201700067

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Abstract

Time‐bin encoding is an attractive method for transmitting photonic qubits over long distances with minimal decoherence. It allows a simple receiver for quantum key distribution (QKD) that extracts a key by measuring time of arrival of photons and detects eavesdropping by measuring interference of pulses in different time bins. In the past, coherent pulses have been generated using a CW laser and an intensity modulator. A greatly simplified transmitter is proposed and demonstrated here that works by directly modulating the laser diode. Coherence between pulses is maintained by a weak seed laser. The modulator‐free source creates time‐bin encoded pulses with a high extinction ratio (29.4 dB) and an interference visibility above 97 %. The resulting QKD transmitter gives estimated secure key rates up to 4.57 Mbit/s, the highest yet reported for coherent‐one‐way QKD, and can be programmed for all protocols using weak coherent pulses.

Highlights

Time-bin encoding is an attractive method for transmitting photonic qubits popularity are discrete variable and distributed phase reference protocols.[9]
4.57 Mbit/s, the highest yet reported for coherent-one-way Quantum key distribution (QKD), and can be a laser with a number of external phase programmed for all protocols using weak coherent pulses
Quantum key distribution (QKD) uniquely allows two parties to exchange secure keys with secrecy guaranteed by the fundamental laws of physics.[1]

Summary

Introduction

Time-bin encoding is an attractive method for transmitting photonic qubits popularity are discrete variable and distributed phase reference protocols.[9]. The quantum transmitter (Alice) is configured for time-bin encoding using a slave laser that is optically seeded by a master laser. An optical attenuator attenuates the non-empty time bins to around 0.1 photons per pulse before transmitting them through the quantum channel, implemented by an optical attenuator, to the quantum receiver (Bob).

Results

Conclusion