Quantum Control of nano-diamond Nitrogen Vacancy spin ensembles

<p dir="ltr">A nano-diamond containing an ensemble of nitrogen-vacancy (NV) colour centres is a powerful tool for many room-temperature quantum technological applications, such as single spin detection in high-resolution magnetometry, biomedical imaging, tracking and drug delivery, quantum metrology with levitated particles amongst others. The NV centres are naturally occurring, photo-stable and bio-compatible quantum systems that can be easily spin-polarized and read-out by optical means at ambient conditions. NV spins have long coherence times even at room temperature which renders them ideal systems for the above-mentioned applications. However, they are susceptible to external perturbations from the surrounding environment, which can lead to strong decoherence. This thesis discusses the coherent quantum control and manipulation of randomly oriented nano-diamonds containing a relatively large number of NV centres. Using different quantum control techniques, the thesis explores coupling of NV spins to their surrounding spin baths in nano-diamonds. A new pulse control technique based on a modified dynamical decoupling sequence is introduced to accurately extract information about the inhomogeneous broadening caused by the surrounding spin bath. Furthermore, the thesis also reports on the challenges encountered in the attempt to observe the non-equilibrium many-body phases of NV ensembles in nano-diamonds subject to periodic Floquet driving.</p>