Spin qubits in solid-state systems are strong contenders for quantum communication, computation and metrology. In this seminar I will introduce two such systems I have studied and their application in room-temperature quantum sensing and spin-photon interfaces. Temperature plays a critical role in all chemical reactions in cells and understanding intracellular temperature variations is crucial for biochemical energetics. In addition, rheology is an integral part of cell morphology, division and transport. It is actively regulated by cells in response to temperature. Despite its importance, intracellular thermometry remains challenging, often obscured by the noise due to local biochemical environments. In the first part of the talk, I will illustrate the dual modal quantum sensor based on NV centres in nanodiamonds, which are capable of simultaneously sensing nanoscale temperature and rheology in viscoelastic fluids and a dynamic cellular environment. This technique offers new avenues for understanding intracellular energetics. Next, I will focus on optically addressable single spin defects in two-dimensional (2d) hexagonal boron nitride (hBN). Spin defects in 2d layered materials offer advantages over their bulk counterparts, as their reduced dimensionality enables more feasible on-chip integration into devices. I will report the first room-temperature optically detected magnetic resonance (ODMR) from single carbon-related defects in hexagonal boron nitride. I will show that either positive or negative ODMR signal is observed for each defect. Based on kinematic models, we relate this bipolarity to highly tuneable internal optical rates. In addition, we resolve an ODMR fine structure in the form of an angle-dependent doublet resonance, indicative of weak but finite zero-field splitting. Our results offer a promising route towards realising a room-temperature spin-photon quantum interface in hexagonal boron nitride.

Dr Qiushi Gu received his BA and MSci degrees from the University of Cambridge, UK. He subsequently joined Mete Atature’s group and obtained his PhD in Physics degree in 2022. His work focuses on using spin manipulation techniques for quantum sensing and information processing. Gu worked with NV centres in nanodiamonds for nanoscale NMR experiments and intracellular temperature and rheology sensing. He also identified the first room-temperature ODMR signatures for single spins in hexagonal boron nitride. His research interest lies in optically addressable quantum systems and their manipulation.