Quantum sensors based on nitrogen–vacancy (NV) centres, a defect found in diamonds, are sensitive detectors of single spins. Jiang-Feng Du’s group uses them to gain new understanding of systems that range from molecules within a cell, to exotic quantum systems.
Imaging molecules in their natural environment allows researchers to understand how structure determines function. “Our goal is to put nanoscale quantum sensors into cells to perform magnetic resonance spectroscopy and imaging on single biomolecules, so we can observe what they look like and how they work,” explains Du. In 2015, his group reported results using NV-based sensors to measure single proteins at room temperature in Science, the first single-biomolecular spin resonance spectroscopy, and, in 2018, single DNA molecules in solution in Nature Methods.
Du’s team also uses NV centres to investigate non-Hermitian systems, quantum systems that exhibit exotic behaviour. Non-Hermitian phenomena have so far not been studied in quantum systems, only in classical systems simulating quantum behaviour.
In a 2019 Science paper and in a 2021 Physical Review Letters paper, Du’s team detail the use of a single NV centre to realize non-Hermitian quantum systems.
Beyond fundamental physics, NV centres are used to study 2D materials and nanomagnetism; in China and Europe, commercial equipment is already available. “In my opinion, quantum sensors are the closest quantum technology to real-world use,” concludes Qi Zhang, a researcher in the group.