451 research outputs found
Robust amplification of Santha-Vazirani sources with three devices
We demonstrate that amplification of arbitrarily weak randomness is possible
using quantum resources. We present a randomness amplification protocol that
involves Bell experiments. We find a Bell inequality which can amplify
arbitrarily weak randomness and give a detailed analysis of the protocol
involving it. Our analysis includes finding a sufficient violation of Bell
inequality as a function of the initial quality of randomness. It has a very
important property that for any quality the required violation is strictly
lower than possible to obtain using quantum resources. Among other things, it
means that the protocol takes a finite amount of time to amplify arbitrarily
weak randomness.Comment: published versio
Statistical ensembles without typicality
Maximum-entropy ensembles are key primitives in statistical mechanics from
which thermodynamic properties can be derived. Over the decades, several
approaches have been put forward in order to justify from minimal assumptions
the use of these ensembles in statistical descriptions. However, there is still
no full consensus on the precise reasoning justifying the use of such
ensembles. In this work, we provide a new approach to derive maximum-entropy
ensembles taking a strictly operational perspective. We investigate the set of
possible transitions that a system can undergo together with an environment,
when one only has partial information about both the system and its
environment. The set of all these allowed transitions encodes thermodynamic
laws and limitations on thermodynamic tasks as particular cases. Our main
result is that the set of allowed transitions coincides with the one possible
if both system and environment were assigned the maximum entropy state
compatible with the partial information. This justifies the overwhelming
success of such ensembles and provides a derivation without relying on
considerations of typicality or information-theoretic measures.Comment: 9+9 pages, 3 figure
Bounding Hilbert Space dimension from Temporal Correlations
Projecte realitzat en col.laboraciĂł amb l'IFCOIn this work, we tackle the problem of assessing the Hilbert space
dimension from the set of correlations obtained when measuring in a nonlocal black box
scheme. The concept of a dimension witness and its recent applications are explored.
We also extend these new ideas to the case of a single local box with measurements at
different times, and provide some examples of dimension criteria for this case
Detection loophole attacks on semi-device-independent quantum and classical protocols
Semi-device-independent quantum protocols realize information tasks - e.g.
secure key distribution, random access coding, and randomness generation - in a
scenario where no assumption on the internal working of the devices used in the
protocol is made, except their dimension. These protocols offer two main
advantages: first, their implementation is often less demanding than
fully-device-independent protocols. Second, they are more secure than their
device-dependent counterparts. Their classical analogous is represented by
random access codes, which provide a general framework for describing one-sided
classical communication tasks. We discuss conditions under which detection
inefficiencies can be exploited by a malicious provider to fake the performance
of semi-device-independent quantum and classical protocols - and how to prevent
it.Comment: 13 pages, 1 figure, published versio
Device-independent tests of classical and quantum dimensions
We address the problem of testing the dimensionality of classical and quantum
systems in a `black-box' scenario. We develop a general formalism for tackling
this problem. This allows us to derive lower bounds on the classical dimension
necessary to reproduce given measurement data. Furthermore, we generalise the
concept of quantum dimension witnesses to arbitrary quantum systems, allowing
one to place a lower bound on the Hilbert space dimension necessary to
reproduce certain data. Illustrating these ideas, we provide simple examples of
classical and quantum dimension witnesses.Comment: To appear in PR
Nonlocality in sequential correlation scenarios
As first shown by Popescu [S. Popescu, Phys. Rev. Lett. 74, 2619 (1995)],
some quantum states only reveal their nonlocality when subjected to a sequence
of measurements while giving rise to local correlations in standard Bell tests.
Motivated by this manifestation of "hidden nonlocality" we set out to develop a
general framework for the study of nonlocality when sequences of measurements
are performed. Similar to [R. Gallego et al., Phys. Rev. Lett. 109, 070401
(2013)] our approach is operational, i.e. the task is to identify the set of
allowed operations in sequential correlation scenarios and define nonlocality
as the resource that cannot be created by these operations. This leads to a
characterisation of sequential nonlocality that contains as particular cases
standard nonlocality and hidden nonlocality.Comment: 13 pages, 3 figure
Axiomatic Characterization of the Quantum Relative Entropy and Free Energy
Building upon work by Matsumoto, we show that the quantum relative entropy
with full-rank second argument is determined by four simple axioms: (i)
Continuity in the first argument; (ii) the validity of the data-processing
inequality; (iii) additivity under tensor products; and (iv) super-additivity.
This observation has immediate implications for quantum thermodynamics, which
we discuss. Specifically, we demonstrate that, under reasonable restrictions,
the free energy is singled out as a measure of athermality. In particular, we
consider an extended class of Gibbs-preserving maps as free operations in a
resource-theoretic framework, in which a catalyst is allowed to build up
correlations with the system at hand. The free energy is the only extensive
and continuous function that is monotonic under such free operations. View
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The impact of type 2 immunity and allergic diseases in atherosclerosis.
Allergic diseases are allergen-induced
immunological disorders characterized by the
development of type 2 immunity and IgE responses. The prevalence of allergic diseases
has been on the rise alike cardiovascular disease (CVD), which affects arteries
of different organs such as the heart, the kidney and the brain. The underlying cause
of CVD is often atherosclerosis, a disease distinguished by endothelial dysfunction,
fibrofatty material accumulation in the intima of the artery wall, smooth muscle cell
proliferation, and Th1 inflammation. The opposed T-cell
identity of allergy and atherosclerosis
implies an atheroprotective role for Th2 cells by counteracting Th1 responses.
Yet, the clinical association between allergic disease and CVD argues against
it. Within, we review different phases of allergic pathology, basic immunological
mechanisms of atherosclerosis and the clinical association between allergic diseases
(particularly asthma, atopic dermatitis, allergic rhinitis and food allergy) and CVD.
Then, we discuss putative atherogenic mechanisms of type 2 immunity and allergic inflammation
including acute allergic reactions (IgE, IgG1, mast cells, macrophages and
allergic mediators such as vasoactive components, growth factors and those derived
from the complement, contact and coagulation systems) and late phase inflammation
(Th2 cells, eosinophils, type 2 innate-like
lymphoid cells, alarmins, IL-4,
IL-5,
IL-9,
IL-13
and IL-17).post-print4164 K
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