Abstract
In this work, we present a reliable, efficient, and tight numerical method for calculating key rates for finite-dimensional quantum key distribution (QKD) protocols. We illustrate our approach by finding higher key rates than those previously reported in the literature for several interesting scenarios (e.g., the Trojan-horse attack and the phase-coherent BB84 protocol). Our method will ultimately improve our ability to automate key rate calculations and, hence, to develop a user-friendly software package that could be used widely by QKD researchers.
Highlights
The possibility of large-scale quantum computers in the near future has spawned the field of quantum-safe cryptography [1]
The second step takes this approximately optimal attack and converts it into a lower bound on the key rate
Our main technical result is to provide a recipe for performing the second step, i.e., for converting a nearoptimal attack into a tight lower bound on the key rate
Summary
The possibility of large-scale quantum computers in the near future has spawned the field of quantum-safe cryptography [1]. Our method provides reliable lower bounds on the key rate with arbitrary tightness for finite-dimensional QKD protocols. It is highly efficient and typically returns a key rate within seconds or less on one’s personal computer. The second step takes this approximately optimal attack and converts it into a lower bound on the key rate Breaking it up into these two steps adds flexibility to our method, in that any algorithm can be employed for the initial minimization of the convex function. [19] invoked the Golden-Thompson inequality which for certain protocols introduces looseness into the calculated key rates
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