Single Rare Earth Ions in Nanoparticles

In our Single Rare Earth Ion project we detect and manipulate single dopant ions inside of nanoparticles with the goal of developing a platform suitable for both quantum computing and communication. A single nanoparticle contains a few hundred dopant ions which can serve as qubits and be addressed individually through their unique transition frequencies.  The physical proximity of these ions due to the small nanoparticle size results in strong ion-ion interactions, which can be harnessed to implement multi-qubit gates. The resulting system would be a nanoscale quantum computer with hundreds of highly connected qubits which are all sources of spin-photon entanglement.

We choose rare earth ions for this experiment due to the fantastic optical and spin coherence they show when doped in solid state crystals. However, they suffer from long emission lifetimes which limits emission rates and makes detection extremely challenging. To overcome this we place the nanoparticles inside an optical microcavity formed by a planar mirror and the mirror-coated tip of an optical fibre, which enhances the emission via the Purcell effect. This drastically reduces the emission lifetime while also improving collection efficiency and photon indistinguishability, thus increasing the overall quality of the emitters and making them more suitable for quantum computing and communication applications.