Quantum computation and simulation with dopants in silicon

Bottom-up dopant engineering in silicon reached a level of control where devices can be reproducibly fabricated at the atomic scale with high yield. This talk focuses on the progress of single dopant atom placement in the context of quantum computation and simulation. Silicon offers a particularly interesting platform for quantum bits (qubits) because when isotopically purified it acts as a “semiconductor vacuum” for spins. This leads to extraordinary coherence that is used to realise donor atom based qubits. One and two qubit gates have been achieved with phosphorus qubits in silicon. High-bandwidth dispersive readout has been implemented and single-shot capability has been demonstrated with this technique. Spatially resolved tunnelling experiments that reveal the spectrum and quantum state image of single atoms and tunnel coupled arrangements of atoms will be discussed. This technique enabled the design and verification of a robust scheme to achieve exchange coupling of an two dimensional array of dopants that is immune to placement errors of the atoms. In addition, the fabrication of strongly coupled donor arrays that represent a hardware implementation of a Hubbard simulator will be presented. Quasi-particle tunnelling maps of spin-resolved states with atomic resolution reveal interference processes from which the entanglement entropy and Hubbard interactions are quantified. This represents a first stepping stone towards artificial quantum matter with up to 30 spins to implement complex highly correlated systems.