Quantum communications and quantum computing hold great promises respectively in terms of provably secure communications and drastic speedup in processing abilities for certain important tasks, thus allowing the computation of problems that are currently intractable even with the most powerful supercomputers. One of the most promising architectures to implement quantum communications and quantum computing is a quantum network, composed of several information processing nodes connected to one another. To process information, each node contains a set of qubits (quantum bits) that are the basic processing units, analogously to computer bits in today's computers. In order to design such nodes, it is necessary to identify a suitable physical system that can act as a qubit. Certain atomic impurities in diamond, called silicon-vacancy centres and consisting of a single silicon atom replacing two neighbouring carbon atoms of the diamond, are promising candidates. They can process information using their spin, which can be thought of as a small magnet tied to the atomic defect and that obeys the laws of quantum mechanics. Information can be encoded in the spin using photons, single light particles. Once encoded in the spin, the information needs to be processed and shared with other spins. The goal of this project is to leverage the properties of these impurities in order to progress towards the realization of a quantum network node. In particular, silicon-vacancy centres have the particularity of being particularly sensitive to vibrations in the diamond, so we aim to generate such vibrations controllably and use them to control the spin and interact with other spins to transfer information among them on a single chip. This is of particular interest because mechanical vibrations can interact with a wide variety of physical systems that could all play a role in a quantum network node, they would thus act as a mediator between vastly different quantum systems that would otherwise not be able to interact. Another important aspect of quantum information is that it can be very fragile and spins can only retain it reliably for a limited amount of time. Another goal is thus to manage to extend that storage time as much as possible. To do so, we take advantage of the presence of other spins in the diamond that belong to the nuclei of certain carbon atoms. These nuclear spins interact very little with their environment and are thus excellent memories into which information can be stored. We thus aim to study how to transfer information between the silicon-vacancy spin that processes information and nuclear spins that store it, and how information can be stored in multiple nuclear spins as long as possible.
