1,749 research outputs found
Entanglement of identical particles and reference phase uncertainty
We have recently introduced a measure of the bipartite entanglement of
identical particles, E_P, based on the principle that entanglement should be
accessible for use as a resource in quantum information processing. We show
here that particle entanglement is limited by the lack of a reference phase
shared by the two parties, and that the entanglement is constrained to
reference-phase invariant subspaces. The super-additivity of E_P results from
the fact that this constraint is weaker for combined systems. A shared
reference phase can only be established by transferring particles between the
parties, that is, with additional nonlocal resources. We show how this nonlocal
operation can increase the particle entanglement.Comment: 8 pages, no figures. Invited talk given at EQIS'03, Kyoto, September,
2003. Minor typos corrected, 1 reference adde
Beyond Landauer erasure
In thermodynamics one considers thermal systems and the maximization of
entropy subject to the conservation of energy. A consequence is Landauer's
erasure principle, which states that the erasure of 1 bit of information
requires a minimum energy cost equal to where is the temperature
of a thermal reservoir used in the process and is Boltzmann's constant.
Jaynes, however, argued that the maximum entropy principle could be applied to
any number of conserved quantities which would suggest that information erasure
may have alternative costs. Indeed we showed recently that by using a reservoir
comprising energy degenerate spins and subject to conservation of angular
momentum, the cost of information erasure is in terms of angular momentum
rather than energy. Here we extend this analysis and derive the minimum cost of
information erasure for systems where different conservation laws operate. We
find that, for each conserved quantity, the minimum resource needed to erase 1
bit of memory is where is related to the average
value of the conserved quantity. The costs of erasure depend, fundamentally, on
both the nature of the physical memory element and the reservoir with which it
is coupled.Comment: 7 pages, 3 figure
A goal programming methodology for multiobjective optimization of distributed energy hubs operation
This paper addresses the problem of optimal energy flow management in multicarrier energy networks
in the presence of interconnected energy hubs. The overall problem is here formalized by a nonlinear
constrained multiobjective optimization problem and solved by a goal attainment based methodology.
The application of this solution approach allows the analyst to identify the optimal operation state of the
distributed energy hubs which ensures an effective and reliable operation of the multicarrier energy
network in spite of large variations of load demands and energy prices. Simulation results obtained on
the 30 bus IEEE test network are presented and discussed in order to demonstrate the significance and
the validity of the proposed method
Is coherence catalytic?
Quantum coherence, the ability to control the phases in superposition states
is a resource, and it is of crucial importance, therefore, to understand how it
is consumed in use. It has been suggested that catalytic coherence is possible,
that is repeated use of the coherence without degradation or reduction in
performance. The claim has particular relevance for quantum thermodynamics
because, were it true, it would allow free energy that is locked in coherence
to be extracted . We address this issue directly with a
careful analysis of the proposal by berg. We find that coherence
be used catalytically, or even repeatedly without limit.Comment: 23 pages with 2 figure
Design strategy of geothermal plants for water dominant medium-low temperature reservoirs based on sustainability issues
A design strategy based on a multidisciplinary approach for a sustainable design of ORC power plants is proposed. The design of a geothermal plant is discussed, with reference to a case study about a geothermal area in Tuscany, in which a geothermal reservoir at 120 °C is estimated to be available at about 500 m of depth. A qualitative model of the reservoir under specific production/reinjection conditions is discussed. Numerical simulation of geothermal reservoirs is considered an important interacting issue, also to synthesize the data and different scenarios studied. Three factors are fundamental: the maximum energy production, in the perspective of a sustainable exploitation strategy (definition of wells depth and siting, fluid rates extracted/reinjected); the chemical characterization of the fluid (to define the minimum reinjection temperature in order to prevent scaling phenomena); the definition of a reinjection strategy (flow rates, number and depths of reinjection wells and distances between them). Key results are the temperature and pressure profiles and stored energy reduction in the reservoir during plant lifetime. A power plant output range of 250-500 kW is considered in order to keep the temperature decrease in the reservoir in a range of 5-10 °C during the expected life of the plant. The case study can be seen also as a general value example to discuss how the sustainability of the medium-low temperature geothermal resource makes the design strategy of these plants different with respect to the other renewable source based power plants
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