A Barrett Kok discrete-event simulation

[Krastanov]

The current Barrett Kok implementation in StatesZoo is the correct one to use in most simulations as it is "analytical" -- someone derived the dynamics and the solution manually and implemented them in a "closed form" which is much more efficient than simulating the dynamics.

However, for pedagogical reasons, it would be quite useful to have a few examples of Barrett Kok dynamics that are explicitly simulated, including using the discrete event simulator to explicitly take care of the multiple rounds (and retries) that the protocol requires.

Potentially, we can have two types of this simulation as well:

• one where the establishment of the spin-spin states is handled as a black box by initialize!
• and one where we explicitly model the coupling between the optical state and the spin (i.e. we put some optical state in the fiber, the quantum channel models various noise effects in the fiber and takes care of accounting for speed of light delays, and then when it reaches the spin it models the interaction between the spin and the state)