  An experimental Quantum Key Distribution (QKD) implementation requires
advanced costly hardware, unavailable in most research environments, making
protocol testing and performance evaluation complicated. Historically, this has
been a major motivation for the development of QKD simulation frameworks, to
allow researchers to obtain insight before proceeding into practical
implementations. Several simulators have been introduced over the recent years.
However, only four are publicly available, only one of which models equipment
imperfections. Currently, no open-source simulator includes all following
capabilities: channel attenuation modelling, equipment imperfections and effect
on key rates, estimation of elapsed time during quantum channel processes, use
of truly random binary sequences for qubits and measurement bases, shared-bit
fraction customization. In this paper, we present NuQKD, an open-source
modular, intuitive simulator, featuring all the above capabilities. NuQKD
establishes communication between two computer terminals, accepts custom inputs
(iterations, raw key size, interception rate etc.) and evaluates the sifted key
length, Quantum Bit Error Rate (QBER), elapsed communication time and more).
NuQKD capabilities include optical fiber and free-space simulation, modeling of
equipment/channel imperfections, bitstrings from True Random Number Generator,
modular design and automated evaluation of performance metrics. We expect NuQKD
to enable convenient and accurate representation of actual experimental
conditions.
