16 research outputs found
Classical Knowledge for Quantum Security
We propose a decision procedure for analysing security of quantum
cryptographic protocols, combining a classical algebraic rewrite system for
knowledge with an operational semantics for quantum distributed computing. As a
test case, we use our procedure to reason about security properties of a
recently developed quantum secret sharing protocol that uses graph states. We
analyze three different scenarios based on the safety assumptions of the
classical and quantum channels and discover the path of an attack in the
presence of an adversary. The epistemic analysis that leads to this and similar
types of attacks is purely based on our classical notion of knowledge.Comment: extended abstract, 13 page
Why the Disjunction in Quantum Logic is Not Classical
The quantum logical `or' is analyzed from a physical
perspective. We show that it is the existence of EPR-like correlation states
for the quantum mechanical entity under consideration that make it
nonequivalent to the classical situation. Specifically, the presence of
potentiality in these correlation states gives rise to the quantum
deviation from the classical logical
`or'. We show how this arises not only in the microworld, but also in
macroscopic situations where EPR-like correlation states are
present. We investigate how application of this analysis to concepts could
alleviate some well known
problems in cognitive science
Distributed measurement-based quantum computation
We develop a formal model for distributed measurement-based quantum
computations, adopting an agent-based view, such that computations are
described locally where possible. Because the network quantum state is in
general entangled, we need to model it as a global structure, reminiscent of
global memory in classical agent systems. Local quantum computations are
described as measurement patterns. Since measurement-based quantum computation
is inherently distributed, this allows us to extend naturally several concepts
of the measurement calculus, a formal model for such computations. Our goal is
to define an assembly language, i.e. we assume that computations are
well-defined and we do not concern ourselves with verification techniques. The
operational semantics for systems of agents is given by a probabilistic
transition system, and we define operational equivalence in a way that it
corresponds to the notion of bisimilarity. With this in place, we prove that
teleportation is bisimilar to a direct quantum channel, and this also within
the context of larger networks.Comment: 17 page
A Geometrical Representation of Entanglement as Internal Constraint
We study a system of two entangled spin 1/2, were the spin's are represented
by a sphere model developed within the hidden measurement approach which is a
generalization of the Bloch sphere representation, such that also the
measurements are represented. We show how an arbitrary tensor product state can
be described in a complete way by a specific internal constraint between the
ray or density states of the two spin 1/2. We derive a geometrical view of
entanglement as a 'rotation' and 'stretching' of the sphere representing the
states of the second particle as measurements are performed on the first
particle. In the case of the singlet state entanglement can be represented by a
real physical constraint, namely by means of a rigid rod.Comment: 10 pages, 3 figures. submitted to International Journal of
Theoretical Physic
Distributed Measurement-based Quantum Computation
International audienc
Classical Knowledge for Quantum Cryptographic Reasoning
AbstractWe prove that quantum key distribution is secure against several types of attacks within the framework of classical knowledge knowledge for quantum systems, a formal model which was developed in [D'Hondt, E. and P. Panangaden, Reasoning about quantum knowledge, in: Proceedings of the 25th Conference on Foundations of Software Technology and Theoretical Computer Science, LNCS 3821, 2005, p. 0544c (to appear), quant-ph/0507176]. In particular we rephrase security as a logical property and use meta-logic reasoning on the finite state machine corresponding to the quantum key distribution protocol. While these security issues have been studied before, it is the logical-based approach that is original here
Large-scale wearable data reveal digital phenotypes for daily-life stress detection
Physiological signals have shown to be reliable indicators of stress in laboratory studies, yet large-scale ambulatory validation is lacking. We present a large-scale cross-sectional study for ambulatory stress detection, consisting of 1002 subjects, containing subjects' demographics, baseline psychological information, and five consecutive days of free-living physiological and contextual measurements, collected through wearable devices and smartphones. This dataset represents a healthy population, showing associations between wearable physiological signals and self-reported daily-life stress. Using a data-driven approach, we identified digital phenotypes characterized by self-reported poor health indicators and high depression, anxiety and stress scores that are associated with blunted physiological responses to stress. These results emphasize the need for large-scale collections of multi-sensor data, to build personalized stress models for precision medicine
Metabolic phenotyping reveals a reduction in the bioavailability of serotonin and kynurenine pathway metabolites in both the urine and serum of individuals living with Alzheimer's disease.
Funder: Medical Research Council; doi: http://dx.doi.org/10.13039/501100000265Funder: Alzheimer's research ukFunder: Alzheimer's societyFunder: InnomedFunder: National Institute for Health Research; doi: http://dx.doi.org/10.13039/501100000272BACKGROUND: Both serotonergic signalling disruption and systemic inflammation have been associated with the pathogenesis of Alzheimer's disease (AD). The common denominator linking the two is the catabolism of the essential amino acid, tryptophan. Metabolism via tryptophan hydroxylase results in serotonin synthesis, whilst metabolism via indoleamine 2,3-dioxygenase (IDO) results in kynurenine and its downstream derivatives. IDO is reported to be activated in times of host systemic inflammation and therefore is thought to influence both pathways. To investigate metabolic alterations in AD, a large-scale metabolic phenotyping study was conducted on both urine and serum samples collected from a multi-centre clinical cohort, consisting of individuals clinically diagnosed with AD, mild cognitive impairment (MCI) and age-matched controls. METHODS: Metabolic phenotyping was applied to both urine (n =â560) and serum (n =â354) from the European-wide AddNeuroMed/Dementia Case Register (DCR) biobank repositories. Metabolite data were subsequently interrogated for inter-group differences; influence of gender and age; comparisons between two subgroups of MCI - versus those who remained cognitively stable at follow-up visits (sMCI); and those who underwent further cognitive decline (cMCI); and the impact of selective serotonin reuptake inhibitor (SSRI) medication on metabolite concentrations. RESULTS: Results revealed significantly lower metabolite concentrations of tryptophan pathway metabolites in the AD group: serotonin (urine, serum), 5-hydroxyindoleacetic acid (urine), kynurenine (serum), kynurenic acid (urine), tryptophan (urine, serum), xanthurenic acid (urine, serum), and kynurenine/tryptophan ratio (urine). For each listed metabolite, a decreasing trend in concentrations was observed in-line with clinical diagnosis: control > MCIâ>âAD. There were no significant differences in the two MCI subgroups whilst SSRI medication status influenced observations in serum, but not urine. CONCLUSIONS: Urine and serum serotonin concentrations were found to be significantly lower in AD compared with controls, suggesting the bioavailability of the neurotransmitter may be altered in the disease. A significant increase in the kynurenine/tryptophan ratio suggests that this may be a result of a shift to the kynurenine metabolic route due to increased IDO activity, potentially as a result of systemic inflammation. Modulation of the pathways could help improve serotonin bioavailability and signalling in AD patients