Progress in exchange-based 2-qubit logic gates with donors in silicon*

Donor spin qubits have been extensively studied for future applications in quantum computing. In top-down ion-implanted devices, coherence times as long as 30 seconds and gate fidelities beyond 99.9% have been demonstrated. Building on those achievements, we report on progress towards two-qubit operations mediated by exchange interactions. Newly fabricated devices with an increased implantation dose revealed a high number of donors in the vicinity of a single-electron transistor. Electron spin resonance (ESR) spectra show spectroscopic evidence of exchange-coupled donor pairs. Experiments are underway to demonstrate 2-qubit logic gates using state-conditional ESR pulses.