Condensed Matter Seminar: "Quantum 'non-Markovianity': new definitions and some recent developments"
Thursday, March 23, 2017
11:30 am - 12:30 pm
Francesco Ciccarello (University of Palermo, NEST, Duke)
While in classical physics the notion of what is Markovian or not is well defined, this is not the case when it comes to open quantum systems. What makes a quantum dynamics Markovian or non-Markovian (NM)? Traditional answers to this question involve the well-known Lindblad master equation (ME) and/or the ability of an open dynamics to be governed by a time-local ME.The last few years, yet, witnessed a thorough revision of such concepts in the attempt to establish in a rigorous way exact criteria for assessing whether or not, and even quantifying, a dynamics is NM. This resulted in a number of NM "measures" that have been put forward. Based on these and a number of further theoretical progresses, the lack of a Lindblad ME or time-local ME turns out not to be a reliable criterion. For instance: there are Markovian dynamics that are not described by a Lindblad ME. On the other hand, open dynamics that are strongly NM can often be shown to fulfill a time-local ME.After reviewing all these new concepts in depth, I will discuss a specific instance of application of non-Markovianity measures from my latest research work: an atom emitting into a disordered medium. In such a case, the occurrence of localized field modes due to Anderson localization makes the atom dynamics non-Markovian, as confirmed by the behavior of non-Markovianity measures against the amount of disorder. The functional shape of this relationship is well reproduced by an effective phenomenological model.