Entangling Electrons and Nuclei in a Four-Qubit, Two-Atom Device in Silicon

Scalable quantum processors require high-fidelity universal quantum logic operations, in a manufacturable physical platform, along with the capacity to couple multiple qubits together over a variable range of length scales. Nuclear spins of ion-implanted donors in silicon have demonstrated record-breaking coherence times, along with high fidelity (> 99%) universal 1 and 2-qubit operations, approaching the fidelity required to perform fault-tolerant quantum computation. However, the same isolation that protects nuclear spins from environmental noise also makes it challenging to couple them over the distances required for large-scale quantum information processing. In this talk, I will present my PhD work on entangling electron and nuclear spin qubits in a four-qubit, two-donor device in silicon. I will start by describing the first experimental demonstration of exchange-based entangling two-qubit gates between electrons bound to individual ³¹P donors. Building on this, I will show how these electron-electron interactions can be harnessed to mediate entangling gates between spatially separated nuclear spins, extending the achievable coupling length scale beyond previous demonstrations. Together, these results complete the toolbox for constructing a scalable spin-based quantum processor in silicon.