347 research outputs found
Modeling on Body Delay Tolerant Network Sink Locality of Wireless Body Area Networks for Different Body Postures
Due to the recent advancements in the field of wireless communication and Wireless Sensor Networks, the Wireless Body Area Networks (WBANs) have become an area of concern for researchers. In military operations, patient monitoring, sports field, among other wireless body area networks is used for real time monitoring and smart sensing for eHealth operations. In these WBAN, disconnections between the body sensors occur quite often and sometimes of significant duration due to the postural mobility nature of the human. These consequently affects the efficiency of the entire network hence the need for Delay Tolerant Network (DTN). The DTN minimizes delays and adapts itself to cope with long delays if they occur. One of the vital mechanisms that can be employed to enhance the efficiency of the network is to determine the optimal postural locality of the sink nod
Modeling on Body Delay Tolerant Network Sink Locality of Wireless Body Area Networks for Different Body Postures
Due to the recent advancements in the field of wireless communication and Wireless Sensor Networks, the Wireless Body Area Networks (WBANs) have become an area of concern for researchers. In military operations, patient monitoring, sports field, among other wireless body area networks is used for real time monitoring and smart sensing for eHealth operations. In these WBAN, disconnections between the body sensors occur quite often and sometimes of significant duration due to the postural mobility nature of the human. These consequently affects the efficiency of the entire network hence the need for Delay Tolerant Network (DTN). The DTN minimizes delays and adapts itself to cope with long delays if they occur. One of the vital mechanisms that can be employed to enhance the efficiency of the network is to determine the optimal postural locality of the sink nod
The impossibility of Landauer's bound for almost every quantum state
The thermodynamic cost of resetting an arbitrary initial state to a
particular desired state is lower bounded by Landauer's bound. However, here we
demonstrate that this lower bound is necessarily unachievable for nearly every
initial state, for any reliable reset mechanism. Since local heating threatens
rapid decoherence, this issue is of substantial importance beyond mere energy
efficiency. For the case of qubit reset, we find the minimally dissipative
state analytically for any reliable reset protocol, in terms of the
entropy-flow vector introduced here. This allows us to verify a recent theorem
about initial-state dependence of entropy production for any finite-time
transformation, as it pertains to quantum state preparation.Comment: 9 pages plus 3 pages of appendices, 3 figure
Initial-State Dependence of Thermodynamic Dissipation for any Quantum Process
New exact results about the nonequilibrium thermodynamics of open quantum
systems at arbitrary timescales are obtained by considering all possible
variations of initial conditions of a system, its environment, and correlations
between them. First we obtain a new quantum-information theoretic equality for
entropy production, valid for an arbitrary initial joint state of system and
environment. For any finite-time process with a fixed initial environment, we
then show that the contraction of the system's distinction -- relative to the
minimally dissipative state -- exactly quantifies its thermodynamic
dissipation. The quantum component of this dissipation is the change in
coherence relative to the minimally dissipative state. Implications for quantum
state preparation and local control are explored. For nonunitary processes --
like the preparation of any particular quantum state -- we find that mismatched
expectations lead to divergent dissipation as the actual initial state becomes
orthogonal to the anticipated one.Comment: 6 pages plus 14 pages of appendices, 1 figur
Building Gaussian Cluster States by Linear Optics
The linear optical creation of Gaussian cluster states, a potential resource
for universal quantum computation, is investigated. We show that for any
Gaussian cluster state, the canonical generation scheme in terms of QND-type
interactions, can be entirely replaced by off-line squeezers and beam
splitters. Moreover, we find that, in terms of squeezing resources, the
canonical states are rather wasteful and we propose a systematic way to create
cheaper states. As an application, we consider Gaussian cluster computation in
multiple-rail encoding. This encoding may reduce errors due to finite
squeezing, even when the extra rails are achieved through off-line squeezing
and linear optics.Comment: 5 Pages, 3 figure
Overarching framework between Gaussian quantum discord and Gaussian quantum illumination
We cast the problem of illuminating an object in a noisy environment into a
communication protocol. A probe is sent into the environment, and the presence
or absence of the object constitutes a signal encoded on the probe. The probe
is then measured to decode the signal. We calculate the Holevo information and
bounds to the accessible information between the encoded and received signal
with two different Gaussian probes---an Einstein-Podolsky-Rosen (EPR) state and
a coherent state. We also evaluate the Gaussian discord consumed during the
encoding process with the EPR probe. We find that the Holevo quantum advantage,
defined as the difference between the Holevo information obtained from the EPR
and coherent state probes, is approximately equal to the discord consumed.
These quantities become exact in the typical illumination regime of low object
reflectivity and low probe energy. Hence we show that discord is the resource
responsible for the quantum advantage in Gaussian quantum illumination.Comment: 12 pages, 8 figure
The use of GNSS zenith total delays in operational AROME/Hungary 3D-Var over a central European domain
The delay of satellite signals broadcasted by Global Navigation Satellite
System (GNSS) provides unique atmospheric observations which endorse
numerical weather prediction from global to limited-area models. Due to the
possibility of its frequent and near-real-time estimation, the zenith total
delays (ZTDs) are valuable information for any state-of-the-art data
assimilation system. This article introduces the data assimilation of ZTDs in
a Hungarian numerical weather prediction system, which was carried out by taking
into account observations from central European GNSS analysis and processing
centres. The importance of ZTD observations is described and shown by a
diagnostic tool in the 3-hourly updated 3D-Var assimilation
scheme. Furthermore, observing system experiments are done to evaluate the
impact of GNSS ZTDs on mesoscale limited-area forecasts. The results of the
use of GNSS ZTDs showed a clear added value to improve screen-level
temperature and humidity forecasts when the bias is accurately estimated and
corrected in the data assimilation scheme. The importance of variational, i.e.
adaptive bias correction, is highlighted by verification scores compared to
static bias correction. Moreover, this paper reviews the quality control of
GNSS ground-based stations inside the central European domain, the
calculation of optimal thinning distance and the preparation of the two
above-mentioned bias correction methods. Finally, conclusions are drawn on
different settings of the forecast and analysis experiments with a brief
future outlook.</p
Entangled-state cycles from conditional quantum evolution
A system of cascaded qubits interacting via the oneway exchange of photons is
studied. While for general operating conditions the system evolves to a
superposition of Bell states (a dark state) in the long-time limit, under a
particular resonance condition no steady state is reached within a finite time.
We analyze the conditional quantum evolution (quantum trajectories) to
characterize the asymptotic behavior under this resonance condition. A distinct
bimodality is observed: for perfect qubit coupling, the system either evolves
to a maximally entangled Bell state without emitting photons (the dark state),
or executes a sustained entangled-state cycle - random switching between a pair
of Bell states while emitting a continuous photon stream; for imperfect
coupling, two entangled-state cycles coexist, between which a random selection
is made from one quantum trajectory to another.Comment: 12 pages, 10 figure
- …