Million‐Atom Wave Function Simulations of a Single Donor Qubit Made in Silicon Utilizing Ion Implantation Technology

A large‐scale quantum computer promises quantum algorithms with an exponential speed increase over classical counterparts. Ion implanted donor atom qubits in isotopically enriched have demonstrated leading coherence times and gate fidelities. Large‐scale donor architectures must be tolerant to positional uncertainties owing to ion straggling consistent with the implant energy required to place near surface donor atoms allowing manipulation by surface control electrodes. These issues are addressed with a 40 million silicon atom quantum model based on the atomistic tight‐binding technique in the context of the flip‐flop qubit architecture. The donor electron wavefunction operates in a state of equal superposition between the buried host donor atom and below the surface gate oxide. Key issues include: donor positional uncertainty from ion straggling coupled with non‐uniform control gate potentials, the coupling of donor wave functions to gate‐defined quantum wells, and the effect of bystander donors including the mitigation of non‐functional adventitious channeled ions by re‐implantation employing deterministic ion implantation. An upper constraint of 9 keV ions minimizes straggling allowing quantum superposition and is compatible with existing fabrication techniques. With heavy donors, such as , the constraints are relaxed because, for a given implant depth, the heavy donors straggle less than light donors.