Passive state preparation in the Gaussian-modulated coherent-states quantum key distribution

Bing Qi, Philip G. Evans, and Warren P. Grice
Phys. Rev. A 97, 012317 – Published 16 January 2018

Abstract

In the Gaussian-modulated coherent-states (GMCS) quantum key distribution (QKD) protocol, Alice prepares quantum states actively: For each transmission, Alice generates a pair of Gaussian-distributed random numbers, encodes them on a weak coherent pulse using optical amplitude and phase modulators, and then transmits the Gaussian-modulated weak coherent pulse to Bob. Here we propose a passive state preparation scheme using a thermal source. In our scheme, Alice splits the output of a thermal source into two spatial modes using a beam splitter. She measures one mode locally using conjugate optical homodyne detectors, and transmits the other mode to Bob after applying appropriate optical attenuation. Under normal conditions, Alice's measurement results are correlated to Bob's, and they can work out a secure key, as in the active state preparation scheme. Given the initial thermal state generated by the source is strong enough, this scheme can tolerate high detector noise at Alice's side. Furthermore, the output of the source does not need to be single mode, since an optical homodyne detector can selectively measure a single mode determined by the local oscillator. Preliminary experimental results suggest that the proposed scheme could be implemented using an off-the-shelf amplified spontaneous emission source.

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  • Received 21 December 2017

DOI:https://doi.org/10.1103/PhysRevA.97.012317

©2018 American Physical Society

Physics Subject Headings (PhySH)

Quantum Information, Science & Technology

Authors & Affiliations

Bing Qi1,2,*, Philip G. Evans1, and Warren P. Grice1

  • 1Quantum Information Science Group, Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 2Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, USA

  • *qib1@ornl.gov

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Vol. 97, Iss. 1 — January 2018

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