Structure of the phase in pure two-mode Gaussian states (7 pages)

R. W. Rendell, A. K. Rajagopal

Alex Monràs

Fabrizio Illuminati, Matteo G. A. Paris, Alessio Serafini

Tudor A. Marian, Paulina Marian

R. W. Rendell, A. K. Rajagopal

The two-mode relative phase associated with Gaussian states plays an important role in quantum information processes in optical, atomic, and electronic systems. In this work, the origin and structure of the two-mode relative phase in pure Gaussian states is studied in terms of its dependences on the quadratures of the modes. This is done by constructing local canonical transformations to an associated two-mode squeezed state. The results are illustrated by studying the time dependence of the phase under a nonlocal unitary model evolution containing correlations between the modes. In a more general context, this approach may allow the two-mode phase to be studied in situations sensitive to different physical parameters within experimental configurations relevant to quantum information processing tasks.

Erik M. Aurell, Lucas Hackl, Mario Kieburg

Abstract We consider ensembles of pure Gaussian states parametrised by single-mode marginals and (optionally) specific mode-mode correlations. Such ensembles provide a model for the final states when isolated quantum systems thermalise, as they can reproduce thermal properties locally, while being globally pure. By an analysis using real replicas and the coherent state representation of Gaussian states we show that the average entanglement entropy of a small subsystem is the same as the von Neumann entropy of a mixed Gaussian state with the same marginals, but no correlations. Finally, we discuss how these ensembles provide a model for Hawking radiation assuming unitary evolution, and discuss some of their properties in relations to the Page curve of Hawking radiation.