From the start of the project, the research focused on creating and testing tiny silicon structures that could link the quantum spins of donor atoms to mechanical motion and light. The team designed, fabricated, and characterized advanced “optomechanical” devices—microscopic silicon beams with built-in optical cavities that react to mechanical vibrations. These devices form the physical platform for connecting the quantum and optical worlds on a chip.
The first stage of the work concentrated on understanding how donor implantation affects the mechanical and optical properties of the devices. This work led to the publication Shakespeare et al., Materials for Quantum Technology (2021) and provided essential guidance for later designs. In parallel, the project built up a strong research team, new cryogenic infrastructure, and international collaborations.
When early measurements did not show the expected quantum coupling signal, the team pursued research avenues to pinpoint the reason for this. One major research avenue was the development of an optical method to read out donor spin states using donor-bound excitons using microfabricated electrodes. First results on this were published as Loippo et al., Physical Review Materials (2023). This technique will provide a new way to monitor the spins independently from their mechanical effects, once the integration to SOI materials is solved.
In parallel, the project achieved significant progress in optomechanical control methods, including a single-laser feedback cooling scheme (Kumar et al., arXiv 2022) and an improved homodyne interferometer for precise optical measurements (la Gala et al., Physical Review Applied 2023). Another important result was the detailed study of photothermal effects, showing that they do not need to limit the operation of the devices (Shakespeare et al., Optics Express 2024).
While the direct observation of spin–mechanical coupling remains a future goal, the project achieved significant progress in technology development, experimental methods, and theoretical understanding. The results of the latter are now in arxiv (Lyyra et al., arXiv 2025 and Hijano et al., arXiv 2025).
The new infrastructure and expertise established through the project have already enabled follow-up research using improved device designs and stronger magnetic coupling schemes. These ongoing efforts continue to build on the project’s foundation, moving closer to the original goals of the project that will in the long-run contribute to practical silicon-based quantum technologies.
