518 research outputs found
Imperfect Bose Gas with Attractive Boundary Conditions
The free Bose gas with attractive boundary conditions is an interesting toy
model for the study of Bose-Einstein Condensation (BEC), because one has BEC
already in one dimension. Here we study for the first time the imperfect Bose
gas with these boundary conditions and prove rigorously the occurence of
condensation.Comment: 8 page
Entropy growth of shift-invariant states on a quantum spin chain
We study the entropy of pure shift-invariant states on a quantum spin chain.
Unlike the classical case, the local restrictions to intervals of length
are typically mixed and have therefore a non-zero entropy which is,
moreover, monotonically increasing in . We are interested in the asymptotics
of the total entropy. We investigate in detail a class of states derived from
quasi-free states on a CAR algebra. These are characterised by a measurable
subset of the unit interval. As the entropy density is known to vanishes,
is sublinear in . For states corresponding to unions of finitely many
intervals, is shown to grow slower than . Numerical
calculations suggest a behaviour. For the case with infinitely many
intervals, we present a class of states for which the entropy increases
as where can take any value in .Comment: 18 pages, 2 figure
Correlations in Free Fermionic States
We study correlations in a bipartite, Fermionic, free state in terms of
perturbations induced by one party on the other. In particular, we show that
all so conditioned free states can be modelled by an auxiliary Fermionic system
and a suitable completely positive map.Comment: 17 pages, no figure
Quantum processes
A number of ideas and questions related to the construction of quantum
processes are discussed. Quantum state extension, entanglement and asymptotic
behaviour of the entropy are some of the issues explored. These topics are
studied in more detail for a class of quantum processes known as finitely
correlated states. Several examples of such processes are presented,
specifically a Free Fermionic model.Comment: 20 pages, 2 figures, to appear in the proceedings of the 46th Karpacz
Winter School of Theoretical Physics "Quantum Dynamics and Information:
Theory and Experiment
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