1,808 research outputs found
On the origin of nonclassicality in single systems
In the framework of certain general probability theories of single systems,
we identify various nonclassical features such as incompatibility, multiple
pure-state decomposability, measurement disturbance, no-cloning and the
impossibility of certain universal operations, with the non-simpliciality of
the state space. This is shown to naturally suggest an underlying simplex as an
ontological model. Contextuality turns out to be an independent nonclassical
feature, arising from the intransitivity of compatibility.Comment: Close to the published versio
Socio-demographic differences of disability prevalence among the population aged 60 years and over in Bangladesh
This study aims to delineate the sociodemographic differences in disability prevalence across the population aged 60 years and over in Bangladesh, and to investigate the association of factors with reporting disability in later life. A microdata sample for those aged 60 years or over from the Census of Bangladesh 2011 was used where disability was assessed with a self-reported single response question. Logistic regression models were performed separately for men and women. Results reveal that the disability prevalence rate increased sharply with age, and it was higher among older women (5.2%) compared to men (4.8%). Physical and vision disabilities were the two categories with the highest prevalence of reported disabilities, with a higher prevalence of physical disability among men and vision disability among women. Being older, female, currently not in marital partnership, and having a lower educational attainment, not being employed, living alone, and residing in the rural areas were significantly associated with reporting disability in later life. The higher prevalence of disability among older women, those who are illiterate, and those residing in rural areas highlights the need for policies prioritising these groups. Special attention should also be given to those who are currently not in marital partnership, particularly women who are living alone
Orthogonal-state-based cryptography in quantum mechanics and local post-quantum theories
We introduce the concept of cryptographic reduction, in analogy with a
similar concept in computational complexity theory. In this framework, class
of crypto-protocols reduces to protocol class in a scenario , if for
every instance of , there is an instance of and a secure
transformation that reproduces given , such that the security of
guarantees the security of . Here we employ this reductive framework to
study the relationship between security in quantum key distribution (QKD) and
quantum secure direct communication (QSDC). We show that replacing the
streaming of independent qubits in a QKD scheme by block encoding and
transmission (permuting the order of particles block by block) of qubits, we
can construct a QSDC scheme. This forms the basis for the \textit{block
reduction} from a QSDC class of protocols to a QKD class of protocols, whereby
if the latter is secure, then so is the former. Conversely, given a secure QSDC
protocol, we can of course construct a secure QKD scheme by transmitting a
random key as the direct message. Then the QKD class of protocols is secure,
assuming the security of the QSDC class which it is built from. We refer to
this method of deduction of security for this class of QKD protocols, as
\textit{key reduction}. Finally, we propose an orthogonal-state-based
deterministic key distribution (KD) protocol which is secure in some local
post-quantum theories. Its security arises neither from geographic splitting of
a code state nor from Heisenberg uncertainty, but from post-measurement
disturbance.Comment: 12 pages, no figure, this is a modified version of a talk delivered
by Anirban Pathak at Quantum 2014, INRIM, Turin, Italy. This version is
published in Int. J. Quantum. Info
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