An NV center as an open quantum system - noise spectroscopy and quantum thermodynamics

The investigation of open quantum systems is extremely wide-ranging and permeates fields as diverse as condensed matter physics, quantum optics, and quantum computation, with the goal of understanding the foundations of decoherence and advancing the performance of quantum-based technologies. A precise knowledge of the interaction of a quantum system with its environment is a crucial prerequisite to effectively hinder the detrimental effect of decoherence via selective decoupling, or to gain partial or full control of the environment itself, enabling complex information transfer and storage protocols that involve entanglement. These techniques represent an asset for the realization of quantum-enhanced devices. However, studying the coupling between a quantum system and its (classic or quantum) environment is often limited by the same lack of information and control that inspires the study in the first place. Thus, a quantum system that is highly controllable and that can be used to gain information on the environment constitutes an attractive tool to approach these problems. This thesis tackles these challenges by exploiting the Nitrogen-Vacancy (NV) center in diamond, which is an ideal candidate for many quantum technologies. The NV center has emerged as a prominent platform to realize quantum-enhanced sensors with unprecedented combination of high sensitivity and spatial resolution at room temperature. In addition, its outstanding spin properties and optical addressability make the NV center an ultra stable quantum platform with tunable interaction with its environment. This thesis addresses two complementary objectives: develop quantum control protocols of the NV spin dynamics to accurately characterize the NV environment, and develop new tools to investigate the thermodynamics aspect of the spin dynamics in contact with an engineered energy reservoir.