The key results of this project fall into a set of categories below, and have been disseminated through 24 peer-reviewed publications and conference and workshop presentations around the world.
The study of near-surface spins proved to be a very rich topic of investigation, and we gained crucial insights into the effects of strain on near-surface donor spins in silicon, as well as understanding the stability of near-surface NV-centres in diamond as a function of different surface treatments and environments. These results will be of key importance for the development of such near-surface spins into practical quantum technologies. A key finding was that an alumina (Al2O3) coating deposited by atomic layer deposition (ALD) helps to protect against the optical instability of the NV- centre under vacuum, making this potentially a key part of extending the use of near-surface NV centres for quantum sensing at cryogenic temperatures. We are in discussions with industry regarding the exploitation of this methodology. [Papers in ACS Photonics (2024) and Phys Rev X (2021)]
We characterised the spin coherence properties of novel spin systems, including tellurium donors in silicon and various rare earth spins. In both cases we discovered useful properties for the development of spin-based quantum technologies. We also explored coupling to spin-waves (magnons) in ultra-thin materials. [Papers in Nature Comms (2023) and Phys Rev Lett (2022)]
We developed new theoretical methods, such as the use of deep learning to characterise the noise environment around a qubit [Paper in PRX Quantum (2021).
We exploited the long coherence times and narrow linewidths of the spins we were studying to explore strong coupling to superconducting resonator and establish methods to create microwave quantum memories. We created a new storage protocol enabling microwave photons to be stored within spins while permitting random access – analogous to how conventional computers store information within memories. [Papers in Phys Rev Lett (2020) and Phys Rev X (2020)]
In addition to these core results from the project, there were a number of important yet unanticipated results to emerge from the project, touching a range of fields:
1) We made major advances in the sensitivity of electron spin resonance, a widely used spectroscopy tool with applications across many branches of science. These have shown sensitivity enhancements by over an order of magnitude, reducing the measurement time required by almost 200-fold. In addition to the scientic papers [J Mag Res (2023, 2023, 2021) and Nature Comms (2021) this work led to a patent and creation of a spin-out company which is providing products to the scientific community.
2) We used our control of coherent donor spins in silicon to explore the phenomenon of time crystals in condensed matter physics [Paper in New J Phys (2020)].
3) Finally, we used our expertise on the control of spins of NV centres in diamond, developed through this project, to make contributions to nanodiamond biosensing through our collaborations in the London Centre for Nanotechnology at UCL. This enabled a major advance in the sensitivity of in-vitro diagnostic tools based on nanodiamonds, with 100,000x fold improvement over the state of the art and permitted single-copy HIV virus detection [Paper in Nature (2020)]
