Prof David Jamieson - The second quantum revolution: the role of donor spins in silicon

Every day we effortlessly apply the products of the first quantum revolution to surf the web, read a newspaper or keep in touch with family and friends. The products are computers, lasers and optical fibres all of which depend on quantum mechanics which gives us the tools to understand not only the material building blocks of the universe but also the materials for semiconductor computer chips, light emitting diodes and marvellous medical diagnostics. These products of the first quantum revolution have revolutionised our society. Now a second quantum revolution is underway that aims to employ devices that directly exploit the strange laws of quantum mechanics including superposition, entanglement and spooky action at a distance. Donor spins in silicon are promising for these devices. We have investigated the properties of single spin qubits made from ion implanted 31P donor atoms in enriched 28Si substrates. The enriched 28Si substrate reduces qubit decoherence from spin coupling to the bath of spin-1/2 29Si nuclei originally present in natural silicon. We have found 31P nuclear spin T2 times of over 30 s are possible. New architectures for quantum computer devices exploit robust qubit entanglement over long distances up to several hundreds of nanometres and relaxes the generally tight constraints on the donor-qubit placement precision to ~20 nm. This lecture describes how we have developed a deterministic ion implantation system to construct precision arrays of single donor atoms that could allow the construction of large-scale quantum computer devices based on donors in silicon in the near term.