A pinboard by
David Hopper

PhD Candidate, University of Pennsylvania


Utilizing multi-color illumination, single spins in diamond can be set to precise quantum states.

Nitrogen-vacancy (NV) centers in diamond are optically active spins locked in place by the surrounding crystal lattice. These spins can be controlled and measured by illuminating them with the proper color of light, ranging from the microwave to visible spectrum. These properties allow researchers to perform experiments on single spins, which are inherently quantum mechanical, at room temperature. This allows for studies exploring how the quantum world interacts with the usual classical world we are familiar with. The study of this spin-environment interaction has also opened the possibility of new types of sensors embedded in a solid state material. A current thrust in the field is to utilize the above properties to build devices that solve currently outstanding problems in engineering and biology by leveraging the underlying quantum technology.

One current hurdle to overcome is that of quantum state preparation, or how well we can prepare our spin state before allowing it to interact with its environment or other spins. Due to the probabilistic nature of quantum mechanics, we only know our spin's initial state (say up or down) to some probability. For NV centers in diamond, we can typically initialize into the down state 80% of the time. The other 20% we had the wrong initial condition, and our results will add noise to our final signal. In addition to this, there are charge fluctuations that limit our ability to maintain our single-spin quality to 75% of the time. Thus in reality, we are only in the desired initial state 60% of the time. The research I have been conducting has shown that we can improve upon these spin and charge initialization percentages, commonly referred to as fidelity, by combining multiple colors of excitation light.