Nitrogen vacancy (NV) color centers are point defects that occur naturally in diamond. They can also be created artificially via standard semiconductor fabrication techniques. Associated with this defect are spin states that can be initialized & read-out optically, and driven coherently with resonant microwaves. The coherence time of NV spins tends to be quite long even at room temperature. For these reasons, NVs are ideally suited for applications in quantum information processing and metrology. In my talk I will discuss how NVs can be used to measure magnetic fields with very high sensitivity and spatial resolution using techniques known from NMR and atomic physics. A key factor that limits sensitivity is decoherence caused by interactions between NV spins and other paramagnetic spin impurities in the surrounding lattice. Understanding and controlling these interactions can therefore lead to enhancements in sensitivity. I will describe an experiment to measure the dynamics of the spin bath by using the NV as a probe. I will also discuss the use of multi-pulse sequences known from NMR to decouple NVs from spins in the bath to increase coherence times. In a different approach, sensitivity can be enhanced by using the spin bath itself as a sensor. A prerequisite, however, is a high degree of polarization of the bath spins. I will describe the use of a technique analogous to sympathetic cooling known in atomic physics to laser cool the bath. Finally, I will end with a discussion of a phase-encoding scheme, inspired by MRI, which can be used to image magnetic fields with nanometerscale spatial resolution. With these improvements, NV sensors will become vital tools that may potentially lead to important breakthroughs in the physical and biological sciences. I will end with a discussion of future prospects of NV-diamond technology and highlight possible applications in sensing, quantum optics, and quantum simulations.

This work was supported by NIST, NSF and DARPA (QuEST, QuASAR, Slow Light programs), U.S. Air Force Office of Scientific Research and the U.S. Army Research Office.

Discovery Park, Birck Nanotechnology Center

Researchers should cite this work as follows:

• Chinmay Belthangady (2014), "Quantum-Assisted Magnetometry with NV Centers in Diamond," https://nanohub.org/resources/20560.

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