Home // International Journal On Advances in Systems and Measurements, volume 8, numbers 1 and 2, 2015 // View article

Robustness of Optimal Basis Transformations to Secure Entanglement Swapping Based QKD Protocols

Authors:
Stefan Schauer
Martin Suda

Keywords: quantum key distribution; optimal basis transformations; imperfect apparatus; Gaussian distribution of angles; security analysis; entanglement swapping

Abstract:
In this article, we discuss the optimality of basis transformations as a security measure for quantum key distribution protocols based on entanglement swapping as well as the robustness of these basis transformations considering an imperfect physical apparatus. To estimate the security, we focus on the information an adversary obtains on the raw key bits from a generic version of a collective attack strategy. In the scenario described in this article, the application of general basis transformations serving as a counter measure by one or both legitimate parties is analyzed. In this context, we show that the angles, which describe these basis transformations, can be optimized compared to the application of a Hadamard operation, which is the standard basis transformation recurrently found in literature. Nevertheless, these optimal angles for the basis transformations have to be precisely configured in the laboratory to achieve the minimum amount for the adversary's information. Since we can not be sure that the physical apparatus is perfect, we will look at the robustness of the optimal choice for the angles. As a main result, we show that the adversary's information can be reduced to an amount of $I_{AE} simeq 0.20752$ when using a single basis transformation and to an amount of $I_{AE} simeq 0.0548$ when combining two different basis transformations. This is less than half the information compared to other protocols using a Hadamard operation and thus represents an advantage regarding the security of entanglement swapping based protocols. Further, we will show that the optimal angles to achieve these results are very robust such that an imperfect configuration does only have an insignificant effect on the security of the protocol.

Pages: 135 to 144

Copyright: Copyright (c) to authors, 2015. Used with permission.

Publication date: June 30, 2015

Published in: journal

ISSN: 1942-261x