Linear Entropy in Quantum Phase Space

Dr Laura Rosales Zarate

Centre for Atom Optics and Ultrafast Spectroscopy

3:30 pm Friday, 23 September 2011, EN313, EN Building, Hawthorn.

Entropy is a measure of loss of information about a physical system. Quantum entropy is commonly defined using the von Neumann entropy and it is related to both information content and thermodynamic behavior. The linear or Renyi entropy measures state purity and can be evaluated using phase-space methods. We consider the Gaussian phase representation that uses a general number conserving Gaussian operator basis, in which any density matrix is expanded in terms of a basis of Gaussian operators, and can be applied for both fermion and boson systems.

In this talk, the evaluation of the Renyi entropy and the coarse-graining entropy using the Gaussian phase-space representation for fermions and bosons is discussed. We evaluate the inner-product of Gaussian phase-space basis set, which is the essential ingredient in calculating the linear entropy. As an application, we show results for the sampled entropy for thermal states and for the reduced entropy for bosonic or fermionic modes coupled to a time-evolving non-Markovian reservoir.

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