Synchronized-Readout for narrowband detection of time-varying electromagnetic fields using solid state spins
The nitrogen vacancy (NV) center in diamond has emerged as a leading physical platform for magnetic field sensing with high spatial resolution. Sensors are constructed by doping diamond chips with shallow surface layers of NV centers (nanometers – micrometers below the diamond surface), which allows magnetic samples of interest to be brought within close proximity to the sensing elements. One very promising direction for this rapidly evolving technology is the detection of nuclear magnetic resonance (NMR) signals from small sample volumes; in fact, sensors based on individual NV centers have even been used to detect NMR from a single molecule bound to the diamond surface. However, a key drawback of most demonstrated NV-NMR sensors is their poor spectral resolution (typically 100 – 1000 Hz). This is much less precise than the spectral resolution of standard, inductively-detected NMR systems (typically 1 – 10 Hz) used for chemical analysis in many labs around the world. The poor spectral resolution of NV-NMR detectors prevents them from resolving Hz-level spectral features needed for chemical structure analysis and molecule identification.
Researchers in the Walsworth lab at Harvard have invented a new technique for designing NV-NMR pulse sequences to overcome this spectral resolution limitation. Using these so-called “synchronized readout” pulse sequences, oscillating magnetic fields can be resolved at the level of < 10-3 Hz, far beyond the requirements for NMR-based chemical analysis. The Harvard team has applied synchronized readout pulse sequences to NV-NMR detection, achieving spectral resolution of about ~1 Hz (comparable to standard NMR) in a detection volume of ~10 pL (roughly 1000´ smaller than the most sensitive standard NMR detector). This technique will provide the basis for a variety of next-generation miniaturized NMR technologies, with applications ranging from high-throughput chemical screening to single-cell NMR fingerprinting.
This research was recently published in Nature.
Intellectual Property Status: Patent(s) Pending