# QIRG Seminar: Wolfgang Duer ## Q&A Tobias Guggemos: can you use these entanglement networks for QKD without the problem of trusted repeater nodes? WD: Yes, because you share a fully entangled state with a certain fidelity. Matteo Pompili: do the resource plots take into account the way and resources used for creating the entangled states? WD: No, the resources shown are for storage, not for the intermediate states - only long time memory qubits. Building up is a different problem. Tim Coopmans: On the long-range communication slides - what is the scaling with? WD: It is scaling of resources and it is constant. Liang Jiang: One potential application is a quantum random access memory. Would be interesting to extend this to the quantum network context. WD: Haven't thought about this, but sounds like a good idea. Quantum control - not new, some people are discussing in other contexts as well. Wojciech Kozlowski: Does the good resource scaling also happen if you scale the number of requests? WD: what is important if the requests are individual or parallel. Yes it does scale. Though the advantage does reduce with the demand size and at a certain point it is better to have a Bell-pair based network. Tim Coopmans: I did not fully understand the part about optimization. Should we in practice perform optimization over purification protocols and protocols to produce GHZ states - will this be different from a Bell pair network? WD: Depending on what state you want to produce you will have a different optimization. However, here we look at optimizing for long-term storage rather than generation/creation. I.e. how many long-lived qubits do you need for your network.