Cost and Routing of CV Quantum Networks
November 11th, 2021 FEDERICO CENTRONE Sorbonne Université

We investigate the capabilities of optical Multimode Gaussian states as quantum communication networks, notably for entanglement routing. In this framework, each agent has access only to his own node and can perform Gaussian local passive operations and measurements on it. If any two agents want to perform quantum teleportation, they need to extract a single entangled pair out of this highly entangled multimode CV quantum state, with the help of the other agents. We compare various protocols for this entanglement routing and benchmark against the physical cost for the creation of such networks, with the help of a squeezing resource theory. Squeezing, in fact, is the only active transformation required to produce Gaussian states and the most challenging to realize in experimental scenarios. Exploring different networks with various topologies, especially those in which the entanglement structure reproduces realistic complex shaped networks, we could describe the salient properties of each type and how these features scale with the size of the network. In this way, we could identify which topologies are cheaper than others in terms of practical feasibility and what strategy is best suited to extract the most entanglement from a quantum network. We discovered that the scaling of the cost of some networks with their magnitude is inherently cheaper and some simple procedures allow us to increase the entanglement in the final pair. In particular, we show that we can use measurements on multiple parallel paths connecting two nodes to increase the negativity in the final entangled pair and we employed this result to devise an entanglement routing protocol that is particularly effective on large complex networks.

Seminar, November 11, 2021, 16:00. Blue Lecture Room

Hosted by Prof Antonio Acín