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Title: Noise Analysis of Simultaneous Quantum Key Distribution and Classical Communication Scheme Using a True Local Oscillator
Authors: Qi, B
Lim, C.C.W 
Keywords: Quantum cryptography
Random number generation
Classical communication
Coherent communication
Coherent receivers
Fiber interferometers
Local oscillators
Photon statistics
Random Numbers
Weak coherent pulse
Phase noise
Issue Date: 2018
Citation: Qi, B, Lim, C.C.W (2018). Noise Analysis of Simultaneous Quantum Key Distribution and Classical Communication Scheme Using a True Local Oscillator. Physical Review Applied 9 (5) : 54008. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Recently, we proposed a simultaneous quantum and classical communication (SQCC) protocol where random numbers for quantum key distribution and bits for classical communication are encoded on the same weak coherent pulse and decoded by the same coherent receiver. Such a scheme could be appealing in practice since a single coherent communication system can be used for multiple purposes. However, previous studies show that the SQCC protocol can tolerate only very small phase noise. This makes it incompatible with the coherent communication scheme using a true local oscillator (LO), which presents a relatively high phase noise due to the fact that the signal and the LO are generated from two independent lasers. We improve the phase noise tolerance of the SQCC scheme using a true LO by adopting a refined noise model where phase noises originating from different sources are treated differently: on the one hand, phase noise associated with the coherent receiver may be regarded as trusted noise since the detector can be calibrated locally and the photon statistics of the detected signals can be determined from the measurement results; on the other hand, phase noise due to the instability of fiber interferometers may be regarded as untrusted noise since its randomness (from the adversary's point of view) is hard to justify. Simulation results show the tolerable phase noise in this refined noise model is significantly higher than that in the previous study, where all of the phase noises are assumed to be untrusted. We conduct an experiment to show that the required phase stability can be achieved in a coherent communication system using a true LO. © 2018 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the »» Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Source Title: Physical Review Applied
ISSN: 23317019
DOI: 10.1103/PhysRevApplied.9.054008
Rights: Attribution 4.0 International
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