Quantum sensing using single spins
The interest of EU-funded researchers in charged nitrogen-vacancy centres was motivated by the quest for a deeper understanding of their unique quantum properties. Moreover, the quantum properties of these impurities hosted in synthetic diamonds can be individually manipulated and probed at room temperature. When measurements are based on properties such as differences between well-defined quantum states, sensors can reach unprecedented precision. Quantum sensing within the QUANTUM METROLOGY (Measuring magnetic monopoles using quantum metrology in diamond) project focused on magnetometers. Nitrogen-vacancies have quantised energy levels that split in the presence of magnetic fields. The shift can be read out to determine the magnitude of the externally applied field. The nitrogen-vacancies' uniqueness stems from their ability to be read out optically; this is known as optically detected magnetic resonance. QUANTUM METROLOGY scientists used a laser beam to initiate the atomic-like systems into a well-known energy state while radiofrequency fields controlled the state coherence. Fluorescence was read out to realise the measurement at the nanoscale, with possible application to molecular structure imaging. To evaluate the performance of nitrogen-vacancies-based magnetic resonance imaging, the 3D landscape of electron spins near a diamond's surface was pictured. Scientists achieved an unprecedented combination of resolution – as low as 0.8 nm – and single-spin sensitivity. The new technique allows determining the location of spin labels in biological systems. On the other hand, applying this technique to magnetometry, vector magnetic field sensitivity can exceed nanoTesla precision. Such high-precision measurements are the ultimate aim for the next year of the QUANTUM METROLOGY project.
Keywords
Single spins, nitrogen-vacancy centres, diamond, magnetic monopoles, quantum metrology
