PhD Defense by Rodrigo A. Thomas
Optical spin-mechanics quantum interface: entanglement and back-action evasion
In the last couple of decades, remarkable progress has been made on controlling of physical systems to their ultimate quantum limits. It has also become more and more clear that a single platform might not be able to realize all the protocols needed in a future quantum information processing network. Hybrid quantum devices attempt to combine fundamentally different systems with high efficiency, harnessing the advantages from its constituent elements. In this thesis, we report the recent developments on the hybrid spin ensemble-mechanics interface which, building up on quantum back-action evasion in the negative mass reference frame , lead to generating an entangled EPR state  between a millimeter-size dielectric membrane and the spin ensemble of 109 atoms. Our results pave the road towards measurement of motion beyond the standard quantum limits of sensitivity, as well as towards teleportation-based protocols in hybrid quantum networks.
 Christoffer B Møller*, Rodrigo A. Thomas*, Georgios Vasilakis, Emil Zeuthen, Yeghishe Tsaturyan, Mikhail Balabas, Kasper Jensen, Albert Schliesser, Klemens Hammerer, and Eugene S Polzik. Quantum back-action-evading measurement of motion in a negative mass reference frame. Nature 547, 191-195 (2017).
 Rodrigo A. Thomas*, Michał Parniak*, Christoffer Østfeldt*, Christoffer B. Møller*, Christian Bærentsen, Yeghishe Tsaturyan, Albert Schliesser, Jürgen Appel, Emil Zeuthen, and Eugene S. Polzik. Entanglement between distant macroscopic mechanical and spin systems. Nature Physics, https://doi.org/10.1038/s41567-020-1031-5 (2020).