In general, our work has been devoted to investigate the emergence of quantum correlations of metrological interest in many-body systems that are in contact with the external environment.
First, we focused on the study of ensemble of atoms that are coupled to the environment in a collective way, meaning that atoms release the energy to the environment together, rather than individually. This behaviour can be achieved by using an optical cavity that acts as an intermediary of the interactions between the atoms and the environment. Notably, the coupling between the atoms and the cavity can be engineered by optical means, which allows to, in turn, engineer the dissipation towards the environment. We provided a systematic analysis of the stationary state achieved by the atomic ensemble when different types of engineered dissipation are compensated by an optical driving. This way, we identified regimes where the collection of atoms relax to a so-called “spin squeezed state”: a particular type of quantum state that provides enhanced sensitivity to external parameters, such as small electric fields.
In a second part of our project, we studied 1D networks of quantum systems that couple independently to the environment, also in an engineered way. We established a general set of conditions that, when satisfied, guarantee that the system will end up behaving like a quantum-entangled clock, i.e. displaying persistent oscillations underpinned by quantum entanglement and powered by dissipation (rather than prevented by it).
Further investigations in our project have analysed related problems in quantum metrology, such as the detection of quantum coherence in dissipative systems, or the reconstruction of quantum states from experimental data aided by neural-networks.
