Single ion implanted donor devices for quantum information processing.

Peter Maunz, Andrew E Hollowell, Daniel Lobser +18 more

Brandon Severin, Tim Botzem, Federico Fedele +12 more

Donor spin qubits in silicon offer one- and two-qubit gates with fidelities beyond 99%, coherence times exceeding 30 seconds, and compatibility with industrial manufacturing methods. This motivates the development of large-scale quantum processors using this platform, and the ability to automatically tune and operate such complex devices. In this work, we present the first machine learning algorithm with the ability to automatically locate the charge transitions of an ion-implanted donor in a silicon device, tune single-shot charge readout, and identify the gate voltage parameters where tunnelling rates in and out the donor site are the same. The entire tuning pipeline is completed on the order of minutes. Our results enable both automatic characterisation and tuning of a donor in silicon devices faster than human experts.

Haolin Huang, Liam G. Thomas, Muhammad Usman +2 more

ABSTRACT 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.

万金银, 王育竹, Liu guo Liang

Hosaka Koichi, Seiji Hosoya, Kashiwagi Hirotsugu +9 more

Nitrogen-vacancy (NV) centers in diamond are gaining attention as room-temperature quantum bits, with potential applications in quantum sensing, quantum information processing, and quantum communication. Precise positioning of NV centers is crucial for creating efficient single-photon sources using optical resonators and quantum memories for quantum interface, etc. Generally, broad ion beam implantation through nanohole fabricated by electron beam lithography has been widely used for precise creation of NV centers. There are several reports of deterministic NV creation by using pulsed fs- or ps-laser irradiations. In addition, focusing ion beam implantation provides a route towards scalable quantum information processing [3-6]. In this study, we are developing an inherently deterministic single-ion implantation method based on a linear Paul trap (LPT) as a single-ion source, since the laser-cooling technique can be applied to the trap system to obtain ultralow-emittance ions and manipulate single ions one by one. The QST system uses doubly charged ions cooled with calcium ions, allowing 100 keV ion implantation in diamond.

Jinyin Wan, Yuzhu Wang, Liang Liu