报告摘要

The resource theory of thermal operations allows one to investigate the ultimate possibilities of quantum states and of nanoscale thermal machines. Whilst fairly general, these results do not apply to continuous variable systems and do not take into account that, in many practically relevant settings, system-environment interactions are effectively bilinear. Here we tackle these issues by focusing on Gaussian quantum states and channels. We provide a complete characterisation of the most general Gaussian thermal operations acting on an arbitrary number of bosonic modes, which turn out to be all embeddable in a Markovian dynamics, and derive a simple geometric criterion establishing necessary and sufficient conditions for state transformations under such operations in the single-mode case, encompassing states with nonzero coherence in the energy eigenbasis (i.e., squeezed states). Our analysis leads to a no-go result for the technologically relevant task of algorithmic cooling: We show that it is impossible to reduce the entropy of a system coupled to a Gaussian environment below its own or the environmental temperature, by means of a sequence of Gaussian thermal operations interspersed by arbitrary (even non-Gaussian) unitaries. These findings establish fundamental constraints on the usefulness of Gaussian resources for quantum thermodynamic processes. [arXiv:1909.06123 (2019)]

报告人简介：Gerardo obtained his PhD from University of Salerno, Italy, in 2007. He joined Nottingham in 2009 as Lecturer after postdoctoral positions in Salerno, Rome and Barcelona, and was promoted to Professor in 2016. His main interests are in the characterisation of quantum coherence and all forms of quantum correlations, including and beyond entanglement, in composite systems. He has contributed significantly to the development of quantum information theory with Gaussian states of continuous variable systems.