13,034 research outputs found
Algebraic Geometry of Matrix Product States
We quantify the representational power of matrix product states (MPS) for
entangled qubit systems by giving polynomial expressions in a pure quantum
state's amplitudes which hold if and only if the state is a translation
invariant matrix product state or a limit of such states. For systems with few
qubits, we give these equations explicitly, considering both periodic and open
boundary conditions. Using the classical theory of trace varieties and trace
algebras, we explain the relationship between MPS and hidden Markov models and
exploit this relationship to derive useful parameterizations of MPS. We make
four conjectures on the identifiability of MPS parameters
Giving New Zealand: Philanthropic Funding 2006
This report provides measurement of New Zealanders' philanthropic funding for the 2005/2006 year and what these funds supported
Approximating the Sachdev-Ye-Kitaev model with Majorana wires
The Sachdev-Ye-Kitaev (SYK) model describes a collection of randomly
interacting Majorana fermions that exhibits profound connections to quantum
chaos and black holes. We propose a solid-state implementation based on a
quantum dot coupled to an array of topological superconducting wires hosting
Majorana zero modes. Interactions and disorder intrinsic to the dot mediate the
desired random Majorana couplings, while an approximate symmetry suppresses
additional unwanted terms. We use random matrix theory and numerics to show
that our setup emulates the SYK model (up to corrections that we quantify) and
discuss experimental signatures.Comment: 7 pages, 2 figure
From the microbiome to the central nervous system, an update on the epidemiology and pathogenesis of bacterial meningitis in childhood [version 1; referees: 3 approved]
In the past century, advances in antibiotics and vaccination have dramatically altered the incidence and clinical outcomes of bacterial meningitis. We review the shifting epidemiology of meningitis in children, including after the implementation of vaccines that target common meningitic pathogens and the introduction of intrapartum antibiotic prophylaxis offered to mothers colonized with Streptococcus agalactiae. We also discuss what is currently known about the pathogenesis of meningitis. Recent studies of the human microbiome have illustrated dynamic relationships of bacterial and viral populations with the host, which may potentiate the risk of bacterial meningitis
Denial of Service in Voice Over IP Networks
In this paper we investigate denial of service (DoS) vulnerabilities in Voice over IP (VoIP) systems, focusing on the ITU-T H.323 family of protocols. We provide a simple characterisation of DoS attacks that allows us to readily identify DoS issues in H.323 protocols. We also discuss network layer DoS vulnerabilities that affect VoIP systems. A number of improvements and further research directions are proposed
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