3,550 research outputs found
Improvement of two-way continuous-variable quantum key distribution with virtual photon subtraction
We propose a method to improve the performance of two-way continuous-variable
quantum key distribution protocol by virtual photon subtraction. The Virtual
photon subtraction implemented via non-Gaussian post-selection not only
enhances the entanglement of two-mode squeezed vacuum state but also has
advantages in simplifying physical operation and promoting efficiency. In
two-way protocol, virtual photon subtraction could be applied on two sources
independently. Numerical simulations show that the optimal performance of
renovated two-way protocol is obtained with photon subtraction only used by
Alice. The transmission distance and tolerable excess noise are improved by
using the virtual photon subtraction with appropriate parameters. Moreover, the
tolerable excess noise maintains a high value with the increase of distance so
that the robustness of two-way continuous-variable quantum key distribution
system is significantly improved, especially at long transmission distance.Comment: 15 pages, 6 figure
Photonic Engineering for CV-QKD over Earth-Satellite Channels
Quantum Key Distribution (QKD) via satellite offers up the possibility of
unconditionally secure communications on a global scale. Increasing the secret
key rate in such systems, via photonic engineering at the source, is a topic of
much ongoing research. In this work we investigate the use of photon-added
states and photon-subtracted states, derived from two mode squeezed vacuum
states, as examples of such photonic engineering. Specifically, we determine
which engineered-photonic state provides for better QKD performance when
implemented over channels connecting terrestrial receivers with Low-Earth-Orbit
satellites. We quantify the impact the number of photons that are added or
subtracted has, and highlight the role played by the adopted model for
atmospheric turbulence and loss on the predicted key rates. Our results are
presented in terms of the complexity of deployment used, with the simplest
deployments ignoring any estimate of the channel, and the more sophisticated
deployments involving a feedback loop that is used to optimize the key rate for
each channel estimation. The optimal quantum state is identified for each
deployment scenario investigated.Comment: Updated reference lis
Noiseless Linear Amplifiers in Entanglement-Based Continuous-Variable Quantum Key Distribution
We propose a method to improve the performance of two entanglement-based
continuous-variable quantum key distribution protocols using noiseless linear
amplifiers. The two entanglement-based schemes consist of an entanglement
distribution protocol with an untrusted source and an entanglement swapping
protocol with an untrusted relay. Simulation results show that the noiseless
linear amplifiers can improve the performance of these two protocols, in terms
of maximal transmission distances, when we consider small amounts of
entanglement, as typical in realistic setups.Comment: Special issue on Quantum Cryptograph
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