Sensing with color centers in diamond
High-resolution thermometry is important tool for the control of complex nanoscale systems. Specifically, non-contact thermometers built from luminescent probes such as quantum dots, rare-earth ions, or color centers provide a non-invasive probe, which could enable in vivo detection and control of intra-cellular processes.
The silicon-vacancy center in diamond (SiV) has recently been investigated in the field of quantum communication due to its favorable optical properties. By observing the spectral emission of these centers, one can utilize these same properties to measure temperature at the nanoscale. Thermometers based on the silicon-vacancy center are all-optical, high-resolution, and efficient, allowing for sub-Kelvin uncertainty in one second. When placed in nanodiamonds, these thermometers are chemically inert and physically robust, making them an ideal candidate for a wide variety of applications.
The ability to monitor sub-kelvin variations over a large range of temperatures can provide insight into both organic and inorganic systems, shedding light on questions ranging from tumor metabolism to heat dissipation in integrated circuits. Moreover, by combining local light-induced heat sources with sensitive nanoscale thermometry, it may be possible to engineer biological processes at the sub-cellular level. Many promising approaches are currently being explored for this purpose, including scanning probe microscopy, Raman spectroscopy, and fluorescence-based measurements using nanoparticles and organic dyes. These methods, however, are often limited by a combination of low sensitivity, bio-incompatibility, or systematic errors owing to changes in the local chemical environment. Our new approach to nanoscale thermometry utilizes the quantum mechanical spin associated with nitrogen vacancy (NV) color centers in diamond. The operational principle of NV-based thermometry relies upon the temperature dependent lattice strain of diamond; changes in the lattice are directly reflected as changes in the spin properties of the NV, which are then optically detected with high spatial resolution.
Probing the Nuclear Spin Environment
Nitrogen vacancy centers interact with the magnetic field produced by C13 nuclei in diamond crystals. Just as the nuclei can affect the NV center, the NV center can be used to manipulate the nuclear spins as well. By using coherent population trapping techniques, we can measure the non-ergodic behavior of these nuclei.