  Quantum communication brings radically new capabilities that are provably
impossible to attain in any classical network. Here, we take the first step
from a physics experiment to a fully fledged quantum internet system. We
propose a functional allocation of a quantum network stack and construct the
first physical and link layer protocols that turn ad-hoc physics experiments
producing heralded entanglement between quantum processors into a well-defined
and robust service. This lays the groundwork for designing and implementing
scalable control and application protocols in platform-independent software. To
design our protocol, we identify use cases, as well as fundamental and
technological design considerations of quantum network hardware, illustrated by
considering the state-of-the-art quantum processor platform available to us
(Nitrogen-Vacancy (NV) centers in diamond). Using a purpose built
discrete-event simulator for quantum networks, we examine the robustness and
performance of our protocol using extensive simulations on a super-computing
cluster. We perform a full implementation of our protocol, where we
successfully validate the physical simulation model against data gathered from
the NV hardware. We first observe that our protocol is robust even in a regime
of exaggerated losses of classical control messages with only little impact on
the performance of the system.We proceed to study the performance of our
protocols for 169 distinct simulation scenarios, including tradeoffs between
traditional performance metrics such as throughput and the quality of
entanglement. Finally, we initiate the study of quantum network scheduling
strategies to optimize protocol performance for different use cases.

Quantum Physics