1. Entangled pairs of photons are generated at entanglement sources and then transmitted along separate fibers. The information contained in these photon-pairs is connected to one another, regardless of the distance between each other.
2. Quantum transactions require exquisite timing, so it is critical to synchronize the photons traveling along fibers of different lengths. We use quantum memories to perform this operation. However, they are not efficient at telecom frequencies, so the telecom photons first need to be processed by a frequency converter, then sent onto the quantum memory buffers for storage.
3. When all four memories are populated with their respective photons, we are ready to perform a transaction called entanglement swapping. Here’s where the magic happens!
4. Photons are released from the center two memory buffers and interact at an interference measurement station. This causes the photons in the outer two memory buffers to be entangled, thus swapping entanglement from their previous pair to now being entangled with another.