1,087 research outputs found
Design and implementation of the node identity internetworking architecture
The Internet Protocol (IP) has been proven very flexible, being able to accommodate all kinds of link technologies and supporting a broad range of applications. The basic principles of the original Internet architecture include end-to-end addressing, global routeability and a single namespace of IP addresses that unintentionally serves both as locators and host identifiers. The commercial success and widespread use of the Internet have lead to new requirements, which include internetworking over business boundaries, mobility and multi-homing in an untrusted environment. Our approach to satisfy these new requirements is to introduce a new internetworking layer, the node identity layer. Such a layer runs on top of the different versions of IP, but could also run directly on top of other kinds of network technologies, such as MPLS and 2G/3G PDP contexts. This approach enables connectivity across different communication technologies, supports mobility, multi-homing, and security from ground up. This paper describes the Node Identity Architecture in detail and discusses the experiences from implementing and running a prototype
Autonomous quantum thermal machine for generating steady-state entanglement
We discuss a simple quantum thermal machine for the generation of
steady-state entanglement between two interacting qubits. The machine is
autonomous in the sense that it uses only incoherent interactions with thermal
baths, but no source of coherence or external control. By weakly coupling the
qubits to thermal baths at different temperatures, inducing a heat current
through the system, steady-state entanglement is generated far from thermal
equilibrium. Finally, we discuss two possible implementations, using
superconducting flux qubits or a semiconductor double quantum dot. Experimental
prospects for steady-state entanglement are promising in both systems.Comment: 14 pages, 4 figure
Entanglement enhances cooling in microscopic quantum fridges
Small self-contained quantum thermal machines function without external
source of work or control, but using only incoherent interactions with thermal
baths. Here we investigate the role of entanglement in a small self-contained
quantum refrigerator. We first show that entanglement is detrimental as far as
efficiency is concerned---fridges operating at efficiencies close to the Carnot
limit do not feature any entanglement. Moving away from the Carnot regime, we
show that entanglement can enhance cooling and energy transport. Hence a truly
quantum refrigerator can outperform a classical one. Furthermore, the amount of
entanglement alone quantifies the enhancement in cooling.Comment: 7 pages, 3 figure
Unifying paradigms of quantum refrigeration: fundamental limits of cooling and associated work costs
In classical thermodynamics the work cost of control can typically be
neglected. On the contrary, in quantum thermodynamics the cost of control
constitutes a fundamental contribution to the total work cost. Here, focusing
on quantum refrigeration, we investigate how the level of control determines
the fundamental limits to cooling and how much work is expended in the
corresponding process. \jona{We compare two extremal levels of control. First
coherent operations, where the entropy of the resource is left unchanged, and
second incoherent operations, where only energy at maximum entropy (i.e. heat)
is extracted from the resource. For minimal machines, we find that the lowest
achievable temperature and associated work cost depend strongly on the type of
control, in both single-cycle and asymptotic regimes. We also extend our
analysis to general machines.} Our work provides a unified picture of the
different approaches to quantum refrigeration developed in the literature,
including algorithmic cooling, autonomous quantum refrigerators, and the
resource theory of quantum thermodynamics.Comment: 17 + 28 pages, 10 figure
Extractable Work from Correlations
Work and quantum correlations are two fundamental resources in thermodynamics
and quantum information theory. In this work we study how to use correlations
among quantum systems to optimally store work. We analyse this question for
isolated quantum ensembles, where the work can be naturally divided into two
contributions: a local contribution from each system, and a global contribution
originating from correlations among systems. We focus on the latter and
consider quantum systems which are locally thermal, thus from which any
extractable work can only come from correlations. We compute the maximum
extractable work for general entangled states, separable states, and states
with fixed entropy. Our results show that while entanglement gives an advantage
for small quantum ensembles, this gain vanishes for a large number of systems.Comment: 5+6 pages; 1 figure. Some minor changes, close to published versio
Quantifying photonic high-dimensional entanglement
High-dimensional entanglement offers promising perspectives in quantum
information science. In practice, however, the main challenge is to devise
efficient methods to characterize high-dimensional entanglement, based on the
available experimental data which is usually rather limited. Here we report the
characterization and certification of high-dimensional entanglement in photon
pairs, encoded in temporal modes. Building upon recently developed theoretical
methods, we certify an entanglement of formation of 2.09(7) ebits in a time-bin
implementation, and 4.1(1) ebits in an energy-time implementation. These
results are based on very limited sets of local measurements, which illustrates
the practical relevance of these methods.Comment: 5 pages, 3 figure
Thermodynamic cost of creating correlations
We investigate the fundamental limitations imposed by thermodynamics for
creating correlations. Considering a collection of initially uncorrelated
thermal quantum systems, we ask how much classical and quantum correlations can
be obtained via a cyclic Hamiltonian process. We derive bounds on both the
mutual information and entanglement of formation, as a function of the
temperature of the systems and the available energy. While for a finite number
of systems there is a maximal temperature allowing for the creation of
entanglement, we show that genuine multipartite entanglement---the strongest
form of entanglement in multipartite systems---can be created at any
temperature when sufficiently many systems are considered. This approach may
find applications, e.g. in quantum information processing, for physical
platforms in which thermodynamic considerations cannot be ignored.Comment: 17 pages, 3 figures, substantially rewritten with some new result
05142 Abstracts Collection -- Disruption Tolerant Networking
From 03.04.05 to 06.04.05, the Dagstuhl Seminar 05142 ``Disruption Tolerant Networking\u27\u27 was held in the International Conference and Research Center (IBFI),
Schloss Dagstuhl.
During the seminar, several participants presented their current
research, and ongoing work and open problems were discussed. Abstracts of
the presentations given during the seminar as well as abstracts of
seminar results and ideas are put together in this paper. The first section
describes the seminar topics and goals in general.
Links to extended abstracts or full papers are provided, if available
New insights into solvent-induced structural changes of C-13 labelled metal-organic frameworks by solid state NMR
Selective C-13-labelling of carboxylate carbons in the linker molecules of flexible metal-organic frameworks (MOFs) makes solid-state NMR spectroscopy very powerful to investigate solvent-induced local structural changes as demonstrated by C-13 and H-1 NMR spectroscopy on the pillared layer MOF DUT-8(Ni). Selective identification of polar solvent-node interactions becomes feasible
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