Simulation, control and sensing in open quantum systems
Prof. Dr. Nir Bar-Gill (Hebrew University, Jerusalem, Israel)

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 and sensing.
I will first describe our work on characterizing noise using robust techniques for quantum control ([1], in collaboration with Ra’am Uzdin). Suppression of such noise can be related to control and cooling of the spin-bath surrounding the NV, using a single optically pumped NV quantum central spin as a refrigerator [2]. I will then present a general theoretical framework we developed for Hamiltonian engineering in an interacting spin system [3]. This framework is applied to the coupling of the spin ensemble to a spin bath, including both coherent and dissipative dynamics [4]. 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.
Finally, if time permits, I will describe our work in using NV-based magnetic microscopy to implement quantum sensing in various modalities. I will present measurements of 2D vdW magnetic materials, and specifically the phase transition of FGT through local imaging of magnetic domains in flakes of varying thicknesses [5], as well as a technique for sensing radical concentrations through the change in the charge state of shallow NVs ([6], in collaboration with Uri Banin).

1. T. Zabelotsky et. al., in preparation.
2. P. Penshin et. al., in preparation.
3. K. I. O. Ben’Attar, D. Farfurnik and N. Bar-Gill, Phys. Rev. Research 2, 013061 (2020).
4. K. I. O. Ben’Attar et. al., in preparation.
5. G. Haim et. al., in preparation.
6. Y. Ninio et. al., ACS Photonics 8, 7, 1917-1921 (2021).