Quantum Mechanics: Axiomatics of Measurements and connections with Computing and Information Retrieval

Stochastic Resonance Phenomena in Quantum Many-Body Systems

aula DOTTORATO - MARTEDI' 22 MAGGIO ore 14.00
  SUSANA HUELGA , University of Hertfordshire

>PRESENTATION: Well recognized expert in quantum
information prcessing and its experimental implementation, Susana Huelga got her degree in Theoretical Physics at the University of Salamanca, Spain, and completed her PhD in Oviedo while working as an assistant. Postdoc at the Clarendon Laboratory of the University of Oxford from 1996, and then at Imperial College in London, became lecturer at the University of Hertfordshire in 2000.

Susana Huelga
  The presence of noise is normally associated with a decrease in the optimal performance of any detection or information processing scheme. However, this is not always the case, as illustrated by the phenomenon of stochastic resonace, where the response of a non-linear system displays a resonant-like dependence on the noise strength.
I will discuss stochastic resonance (SR) effects in weakly driven coupled quantum systems. I will show that both dynamical and information theoretic measures of the system's response can be introduced that exhibit a non-monotonic behaviour as a function of the noise strength. The relation between lack of monotonicity in the response and the presence of quantum correlations will be analyzed, showing that there are parameter regimes where the breakdown of a linear response can be associated to the presence of entanglement. I will also argue that a chain of coupled spin systems can exhibit a form of array-enhanced response, where the sensitivity of a single resonator to a weak driving signal is enhanced as a result of the nearest-neighbour coupling. These results enlarge the domain where SR effects exist and should be observable, for instance, in state-of-the-art arrays of superconducting qubits.