Photon-photon and spin-spin Entanglement using Diamond-based impurity Elements: Silicon, Tin And Lead

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Quantum technologies promise revolutionary capabilities in processing information and transmitting with security over a network certified by the principles of quantum physics. The key hardware element of a quantum network is the ‘node’, where a stationary qubit cluster perform primitive processes and communicate with other nodes by exchanging flying qubits. The interfacing between the stationary qubit cluster and the flying qubits is realised by a special ‘broker qubit’. Today, the most competitive candidates for flying and stationary qubits are photons and diamond spins, respectively, and this opportunity is being pursued worldwide. A specific emitter in diamond, the Nitrogen Vacancy (NV), has enabled landmark demonstrations of basic quantum building blocks, but faces fundamental challenges on reaching the optical qualities required to scale up. PEDESTAL offers an efficiency boost to the NV while building on key advances in diamond technology. Our goal is to create a quantum node hardware prototype with characteristics required to sustain a multi-purpose quantum network capable of implementing simultaneous quantum communications and computing. PEDESTAL will develop a demonstrator quantum node based on diamond group-4 spins, which offer specifications outperforming others. Benchmarking against the known silicon-vacancy (SiV) centre, our workhorse will be the tin-vacancy (SnV) centre, which we have shown to have outstanding qualities satisfying the requirements for a quantum node. In parallel, we will develop to maturity the less-known but highly promising lead-vacancy (PbV) centre which can operate with more feasible conditions and develop a novel technique to control spins. Our objectives include creating multi-spin and multi-photon entangled states as resource and will complete its key objectives with the demonstration of distributed three-spin entanglement, culminating in the experimental demonstration of a high-fidelity, high-bandwidth multi-node quantum network