Speaker
Description
Nitrogen-vacancy (NV) centers in diamond are promising quantum sensors for nuclear magnetic resonance (NMR) on micro- and nanoscale sample volumes. At the Bucher Group, we are developing this technology to probe microscopic and complex biological systems. A key challenge is sensitivity: Small samples contain fewer nuclear spins and therefore generate weak NMR signals. In ensemble NV sensing, this weak signal is detected through a spin-dependent change in fluorescence. However, optical readout has limited contrast and photon collection efficiency, so only a fraction of the spin-state information is converted into a measurable optical signal in each cycle. Repetitive readout (RR) addresses this limitation by improving the effective readout fidelity.
RR is based on a concept from quantum information experiments: spin information can be transferred from one quantum system to another. In NV centers, the optically readable electron spin can be coupled to a nearby nuclear spin, which acts as a longer-lived memory. The spin information is first stored in this nuclear spin memory and then repeatedly mapped back onto the electron spin, where it can be read out optically. This RR process increases the information obtained from one spin-state preparation, improving the signal-to-noise ratio per cycle and thereby increasing the sensitivity of NV-based NMR measurements.
The aim of this work is to implement and evaluate RR as a modular sensitivity enhancement for existing ensemble NV-NMR measurement protocols. Once implemented, it will be incorporated into different experimental schemes. We will further investigate extensions of the RR protocol and explore their combination with other sensitivity-enhancement strategies to further improve sensitivity. By improving the detection of weak signals, RR can enable NV-NMR measurements on smaller and more challenging microscopic systems, including biological samples and cell-like systems.
