Open Quantum Systems: Theory and Real World
by Filippo Caruso
Wednesday, 24 May 2017 from to (Europe/Rome)
Only ideally quantum systems are closed, i.e. isolated from the rest, since they do always interact with the external environment, unavoidably affecting its coherence properties and inducing noise effects, leading to so-called open quantum systems. Here, we will first show this deleterious role of the environment where some information coming from the system is irreversibly lost. Then, we will discuss how there might be a back-flow of information from the environment to the system, with the dynamics showing noise time correlations and memory (non-Markovian) effects. However, reversing this traditional point of view, the environment may play also a crucial positive role in remarkably enhancing the quantum system performance to achieve a given task, e.g. noise-assisted transmission of energy and information. Additionally, one can often exploit optimal control theory to manipulate part of the environment, and steer the system dynamics while being only restricted by the so-called quantum speed limit. Moreover, since the environment does continuously 'observe' the physical system, quantum Zeno phenomena may also arise, and be analytically studied in terms of stochastic quantum measurements by large deviation theory. Finally, the fragility of the coherence properties of the dynamical evolution against the environment noise can become an efficient tool to convert the system into a quantum probe of external complex (even classical) objects, towards novel quantum sensing schemes. All these theoretical analytical and numerical results, beyond their foundational role for a deeper understanding of quantum physics, have been also experimentally tested using several platforms including photonics, atomic and bio-molecular systems, with very promising and powerful real-life applications in quite different fields ranging from quantum communication to quantum biology, from quantum computation to quantum metrology.