Speaker: Prof. Francesco Pepe, Università di Bari
Title: "Foundations and phenomenology of decoherence"
By a tautological definition, quantum decoherence labels any process that causes a decrease of quantum coherence, namely of the information, encoded in the state of a system, that allows to observe quantum interference phenomena. Since the complexity of quantum states is essential for the effectiveness of quantum protocols, the detrimental action of decoherence represents a major obstruction to achieving quantum advantages. In this seminar, I will first discuss how decoherence has its roots in entanglement, which is at the same time the most powerful resource for quantum technologies. Then, I will outline the phenomenology of relevant and paradigmatic decoherence processes, such as amplitude damping and phase damping. I will show how the open-system formalism allows to describe random errors affecting the state of a quantum bit (qubit) and destroying the entanglement inside a quantum register. Finally, the coherence-vs-scalability tradeoff, that imposes constraints on the implementation of quantum algorithms on realistic platforms, will be briefly discussed, along with possible strategies to control decoherence.