Coherent control of a donor-molecule electron spin qubit in silicon

Abstract Donor spins in silicon provide a promising material platform for large scale quantum computing. Excellent electron spin coherence times of $${T}_{2}^{* }=268$$ T 2 * = 268 ? s with fidelities 99.9% have been demonstrated isolated phosphorus donors isotopically pure 28 Si, where are local-area-implanted nanoscale MOS device. Despite robust single qubit gates, realising two-qubit exchange gates using this technique is challenging due to the statistical nature dopant implant and placement process. In parallel precision scanning probe lithography route has developed place donor molecules on one atomic plane high accuracy aligned heavily doped in-plane gates. Recent results fast (0.8 ns) gate two P placed 13 nm apart nat Si. paper we demonstrate coherent oscillations molecule Si patterned by tunneling microscope (STM) lithography. The exhibits excellent properties, $${T}_{2}$$ decoherence time 298 ± 30 s, }$$ dephasing 295 23 ns.