The study of open quantum systems, quantum thermodynamics and quantum many-body spin physics in realistic solid-state platforms, has been a long-standing goal in quantum and condensed-matter physics. In this talk I will address these topics through the platform of nitrogen-vacancy (NV) spins in diamond, in the context of purification (or cooling) of a spin bath as a quantum resource and for enhanced metrology. I will first describe a general theoretical framework we developed for Hamiltonian engineering in an interacting spin system . I will then extend this framework to coupling of the spin ensemble to a spin bath, including both coherent and dissipative dynamics . Using these tools I will present a scheme for efficient purification of the spin bath, surpassing the current state-of-the-art and providing a path toward applications in quantum technologies, such as enhanced MRI sensing.
The study of many-body quantum systems, and specifically spin systems, is a main pillar of quantum physics. As part of this research direction, various experimental platforms have emerged which allow for controlled experiments in this context, with nitrogen vacancy (NV) ensembles in diamond being one of them. In order to realize relevant experiments in the NV system, advanced controlled schemes are required in order to generate the required interacting spin Hamiltonians, as well as to robustly control such dense spin ensembles. Here we tackle both issues: we develop a framework for Hamiltonian engineering based on the icosahedral symmetry group, demonstrating its advantages over existing schemes in terms of obtainable interacting Hamiltonians; we develop and demonstrate robust control pulses based on rapid adiabatic passage (RAP), which result in improved coherence times and sensing.