1,207 research outputs found
Information geometric approach to the renormalisation group
We propose a general formulation of the renormalisation group as a family of
quantum channels which connect the microscopic physical world to the observable
world at some scale. By endowing the set of quantum states with an
operationally motivated information geometry, we induce the space of
Hamiltonians with a corresponding metric geometry. The resulting structure
allows one to quantify information loss along RG flows in terms of the
distinguishability of thermal states. In particular, we introduce a family of
functions, expressible in terms of two-point correlation functions, which are
non increasing along the flow. Among those, we study the speed of the flow, and
its generalization to infinite lattices.Comment: Accepted in Phys. Rev.
Area laws in quantum systems: mutual information and correlations
The holographic principle states that on a fundamental level the information
content of a region should depend on its surface area rather than on its
volume. This counterintuitive idea which has its roots in the nonextensive
nature of black-hole entropy serves as a guiding principle in the search for
the fundamental laws of Planck-scale physics. In this paper we show that a
similar phenomenon emerges from the established laws of classical and quantum
physics: the information contained in part of a system in thermal equilibrium
obeys an area law. While the maximal information per unit area depends
classically only on the number of microscopic degrees of freedom, it may
diverge as the inverse temperature in quantum systems. A rigorous relation
between area laws and correlations is established and their explicit behavior
is revealed for a large class of quantum many-body states beyond equilibrium
systems.Comment: 5 pages, 2 figures, published version with appendi
Entanglement in squeezed two-level atom
In the previous paper, we adopted the method using quantum mutual entropy to
measure the degree of entanglement in the time development of the
Jaynes-Cummings model. In this paper, we formulate the entanglement in the time
development of the Jaynes-Cummings model with squeezed states, and then show
that the entanglement can be controlled by means of squeezing.Comment: 6 pages, 5 figures, to be published in J.Phys.
A generalized skew information and uncertainty relation
A generalized skew information is defined and a generalized uncertainty
relation is established with the help of a trace inequality which was recently
proven by J.I.Fujii. In addition, we prove the trace inequality conjectured by
S.Luo and Z.Zhang. Finally we point out that Theorem 1 in {\it S.Luo and
Q.Zhang, IEEE Trans.IT, Vol.50, pp.1778-1782 (2004)} is incorrect in general,
by giving a simple counter-example.Comment: to appear in IEEE TI
Particle Propagation on a Circle with a Point Interaction
We study a particle propagation on a circle in the presence of a point
interaction. We show that the one-particle Feynman kernel can be written into
the sum of reflected and transmitted trajectories which are weighted by the
elements of the n-th power of the scattering matrix evaluated on a line with a
point interaction. As a by-product we find three-parameter family of trace
formulae as a generalization of the Poisson summation formula.Comment: 21 pages, 12 figure
Correlation function and mutual information
Correlation function and mutual information are two powerful tools to
characterize the correlations in a quantum state of a composite system, widely
used in many-body physics and in quantum information science, respectively. We
find that these two tools may give different conclusions about the order of the
degrees of correlation in two specific two-qubit states. This result implies
that the orderings of bipartite quantum states according to the degrees of
correlation depend on which correlation measure we adopt.Comment: 4.2 pages, 4 figure
Extension of Information Geometry to Non-statistical Systems: Some Examples
Our goal is to extend information geometry to situations where statistical
modeling is not obvious. The setting is that of modeling experimental data.
Quite often the data are not of a statistical nature. Sometimes also the model
is not a statistical manifold. An example of the former is the description of
the Bose gas in the grand canonical ensemble. An example of the latter is the
modeling of quantum systems with density matrices. Conditional expectations in
the quantum context are reviewed. The border problem is discussed: through
conditioning the model point shifts to the border of the differentiable
manifold.Comment: 8 pages, to be published in the proceedings of GSI2015, Lecture Notes
in Computer Science, Springe
Molecular epidemiology of infectious bursal disease virus in Zambia
Nucleotide sequences of the VP2 hypervariable region (VP2-HVR) of 10 infectious bursal disease viruses detected in indigenous and exotic chickens in Zambia from 2004 to 2005 were determined. Phylogenetic analysis showed that the viruses diverged into two genotypes and belonged to the African very virulent types (VV1 and VV2). In the phylogenetic tree, strains in one genotype clustered in a distinct group and were closely related to some strains isolated in western Africa (VV1), with nucleotide similarities of 95.7%â 96.5%. Strains in the other genotype were clustered within the eastern African VV type (VV2), with nucleotide similarities of 97.3%â 98.5%. Both genotypes were distributed in the southern parts of Zambia and had a unique conserved amino acid substitution at 300 (EâA) in addition to the putative virulence marker at positions 222(A), 242(I), 256(I), 294(I) and 299(S). These findings represent the first documentation of the existence of the African VV-IBDV variants in both indigenous and exotic chickens in Zambia
Complementarity and the algebraic structure of 4-level quantum systems
The history of complementary observables and mutual unbiased bases is
reviewed. A characterization is given in terms of conditional entropy of
subalgebras. The concept of complementarity is extended to non-commutative
subalgebras. Complementary decompositions of a 4-level quantum system are
described and a characterization of the Bell basis is obtained.Comment: 19 page
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