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arXiv:1803.09158 · Physical Review A

Gaussian one-way thermal quantum cryptography with finite-size effects

Panagiotis Papanastasiou, Carlo Ottaviani, Stefano Pirandola

Published Sep 11, 2018• 24 citations
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Abstract

We study the impact of finite-size effects on the security of thermal one-way quantum cryptography. Our approach considers coherent and/or squeezed states at the preparation stage, on the top of which the sender adds trusted thermal noise. We compute the key rate incorporating finite-size effects, and we obtain the security threshold at different frequencies. As expected, finite-size effects deteriorate the performance of thermal quantum cryptography. Our analysis is useful to quantify the impact of this degradation on relevant parameters like tolerable attenuation and transmission frequencies at which one can achieve security.

DOI
10.1103/physreva.98.032314

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We study the security of two-way quantum cryptography at different wavelengths of the electromagnetic spectrum, from the optical down to the microwave range. In particular, we consider a two-way quantum communication protocol where Gaussian-modulated thermal states are subject to random Gaussian displacements and finally homodyned. We show how its security threshold (in reverse reconciliation) is extremely robust with respect to the preparation noise and able to outperform the security thresholds of one-way protocols at any wavelength. As a result, improved security distances are now accessible for implementing quantum key distribution in the very challenging regime of infrared frequencies.
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A general study of arbitrary finite-size coherent attacks against continuous-variable quantum cryptographic schemes is presented. It is shown that, if the size of the blocks that can be coherently attacked by an eavesdropper is fixed and much smaller than the key size, then the optimal attack for a given signal-to-noise ratio in the transmission line is an individual Gaussian attack. Consequently, non-Gaussian coherent attacks do not need to be considered in the security analysis of such quantum cryptosystems.
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