Quantum technology capital: Multi-species single-ion implantation

The exploitation of single atoms for Quantum Technologies (QT) is most advanced for single-atom and single-ion electromagnetic traps in vacuum. Dopants in solids provide a natural form of trapping, as the impurity is held in place by the electromagnetic fields of the host solid around it, but on a length scale orders of magnitude smaller. Some solids, such as silicon can be made with an astonishing purity of 1 part per 100,000,000,000. This is so pure that nano-scale devices can be expected to have zero unintentional impurities and, if the doping is carefully controlled, a device can be constructed with a single, solitary impurity atom opening up a wealth of possibilities for solid state QT. This brings new challenges in engineering the local environment, but they are ideal objects for robust, reproducable QT applications. Single dopants provide 'qubits' of quantum information for clocks, sensors and computation, and non- classical light sources for quantum key distribution systems, quantum repeaters, quantum lithography, multivalent logic and local sensing. The first electronic observation of a single impurity in a semiconductor was made in a MOSFET device cooled to about 30K - the single, naturally occurring, unidentified bistable impurity close to the conduction channel produced random telegraph noise. Single electron transistor channels now allow specific nearby dopants to be identified by their effect on the electrical characteristics. In some cases single impurities may be incorporated with nanometre precision using Scanning Tunnelling Microscope tips, but a much greater variety could, in principle, be achieved with ion implantation. Ion implantation is a microelectronic industry standard technique, and Surrey University houses the UK National Ion Beam Centre. Although implantation with a lateral accuracy of about 20 nm has been reported, it has only previously been possible with lithographically produced masks. This has already been used to create active devices that involve two phosphorus atoms in silicon close enough for their spins to exchange in a flip-flop interaction, but the functionality of this device was restricted by the limited accuracy of the implantation technique, and it has not been reproduced. A much more scalable, reproducible technology would be to use highly focused ion beams, but this requires a significant advancement in implantation tools. This proposal is to install the world's first single ion implantation tool with 20nm lateral beam focus, with the ability to implant any species from gas or solid source. The tool will serve the UK need for an open access user facility for academia and industry in QTs. Using this tool, we will enable implantation of single bismuth atoms in silicon, single nitrogen atoms in diamond, single erbium atoms in sapphire, and single manganese atoms in GaAs. Each of these exemplifies a different QT platform and covers applications from magnetometry to imaging, computation and single photon emission. We will characterize and image the single atom devices, either via collaboration with key partners (in the case of diamond NV) or in house (in the case of Bi in Si). In the case of the Si:Bi (and other silicon shallow impurities) we will install a world leading near-field imaging system using terahertz frequency light. This will take advantage of Surrey's strategic partnership with the National Physical Laboratory (NPL).