764 research outputs found
Quantum Key Distribution without sending a Quantum Signal
Quantum Key Distribution is a quantum communication technique in which random
numbers are encoded on quantum systems, usually photons, and sent from one
party, Alice, to another, Bob. Using the data sent via the quantum signals,
supplemented by classical communication, it is possible for Alice and Bob to
share an unconditionally secure secret key. This is not possible if only
classical signals are sent. Whilst this last statement is a long standing
result from quantum information theory it turns out only to be true in a
non-relativistic setting. If relativistic quantum field theory is considered we
show it is possible to distribute an unconditionally secure secret key without
sending a quantum signal, instead harnessing the intrinsic entanglement between
different regions of space time. The protocol is practical in free space given
horizon technology and might be testable in principle in the near term using
microwave technology
Modeling the Effects of Multiple Myeloma on Kidney Function
Multiple myeloma (MM), a plasma cell cancer, is associated with many health
challenges, including damage to the kidney by tubulointerstitial fibrosis. We
develop a mathematical model which captures the qualitative behavior of the
cell and protein populations involved. Specifically, we model the interaction
between cells in the proximal tubule of the kidney, free light chains, renal
fibroblasts, and myeloma cells. We analyze the model for steady-state solutions
to find a mathematically and biologically relevant stable steady-state
solution. This foundational model provides a representation of dynamics between
key populations in tubulointerstitial fibrosis that demonstrates how these
populations interact to affect patient prognosis in patients with MM and renal
impairment.Comment: Included version of model without tumor with steady-state analysis,
corrected equations for free light chains and renal fibroblasts in model with
tumor to reflect steady-state analysis, updated abstract, updated and added
reference
Gaussian Post-selection for Continuous Variable Quantum Cryptography
We extend the security proof for continuous variable quantum key distribution
protocols using post selection to account for arbitrary eavesdropping attacks
by employing the concept of an equivalent protocol where the post-selection is
implemented as a series of quantum operations including a virtual distillation.
We introduce a particular `Gaussian' post selection and demonstrate that the
security can be calculated using only experimentally accessible quantities.
Finally we explicitly evaluate the performance for the case of a noisy Gaussian
channel in the limit of unbounded key length and find improvements over all
pre-existing continuous variable protocols in realistic regimes.Comment: 4+4 pages. arXiv admin note: substantial text overlap with
arXiv:1106.082
Munchausen Syndrome by Proxy: Identification and Intervention
Munchausen Syndrome by Proxy (MSBP), also known as “factitious disorder by proxy,” is a mental illness in which a person lies about the physical or mental well-being of a person he/she is responsible for (The Cleveland Clinic, 2008). Most often the dynamic transpires between a mother and her child. The motivation behind MSBP is that the adult seeks the attention typically given to those who are sick, and attempts to get the attention by causing or lying about illness in his/her child. MSBP is a type of child abuse and can result in long-term physical and psychological effects or even death (Roesler & Jenny, 2009). ...
The mental illness of MSBP is a label given to adults, and MSBP as well as its cousin Munchausen Syndrome (in which individuals feign disease, illness, or psychological trauma in themselves to draw sympathy) are both adult-onset disorders. However, children are affected severely by this disorder, as evidenced by the above case study. Children who are abused by MSBP often are chronically absent from school, are subjected to numerous, painful, unnecessary medical procedures, are physically and mentally abused by parents, and suffer long-term psychological damage if they survive the abuse (Sheridan, 2003)
Quantum Communication with an Accelerated Partner
An unsolved problem in relativistic quantum information research is how to
model efficient, directional quantum communication between localised parties in
a fully quantum field theoretical framework. We propose a tractable approach to
this problem based on solving the Heisenberg evolution of localized field
observables. We illustrate our approach by analysing, and obtaining approximate
analytical solutions to, the problem of communicating coherent states between
an inertial sender, Alice and an accelerated receiver, Rob. We use these
results to determine the efficiency with which continuous variable quantum key
distribution could be carried out over such a communication channel.Comment: Additional explanatory text and typo in Eq.17 correcte
“Don't you want to stay?” The impact of training and recognition as human resource practices on volunteer turnover
Managing volunteers is a difficult undertaking. This study draws on human resource (HR) management theory and literature to investigate the effect of two HR practices—training and recognition—on volunteer turnover. We use longitudinal administrative data collected by an Indiana nonprofit organization, which contains individual volunteer characteristics, organizational HR practices, and information on actual turnover behavior. We found that recognizing volunteer contributions with awards predicted volunteer retention in the following year. Training did not have a direct effect on volunteer turnover, but interacted with gender; men who received training were more likely to stay than women. The study contributes to the literature on HR management in the volunteer context, adds to the emerging literature on awards as incentives for volunteers, and addresses the common method bias by using longitudinal data
Optimal realistic attacks in continuous-variable quantum key distribution
Quantum cryptographic protocols are typically analysed by assuming that
potential opponents can carry out all physical operations, an assumption which
grants capabilities far in excess of present technology. Adjusting this
assumption to reflect more realistic capabilities is an attractive prospect,
but one that can only be justified with a rigorous, quantitative framework that
relates adversarial restrictions to the protocols security and performance. We
investigate the effect of limitations on the eavesdropper's (Eve's) ability to
make a coherent attack on the security of continuous-variable quantum key
distribution (CV-QKD). We consider a realistic attack, in which the total
decoherence induced during the attack is modelled by a Gaussian channel. Based
on our decoherence model we propose an optimal hybrid attack, which allows Eve
to perform a combination of both coherent and individual attacks
simultaneously. We evaluate the asymptotic and composable finite-size security
of a heterodyne CV-QKD protocol against such hybrid attacks in terms of Eve's
decoherence. We show that when the decoherence is greater than a threshold
value, Eve's most effective strategy is reduced to the individual attack. Thus,
if we are willing to assume that the decoherence caused by the memory and the
collective measurement is large enough, it is sufficient to analyse the
security of the protocol only against individual attacks, which significantly
improves the CV-QKD performance in terms of both the key rate and the maximum
secure transmission distance.Comment: 11 pages, 4 figure
Teleportation-based collective attacks in Gaussian quantum key distribution
In Gaussian quantum key distribution eavesdropping attacks are conventionally modeled through the universal entangling cloner scheme, which is based on the premise that the whole environment is under control of the adversary, i.e., the eavesdropper purifies the system. This assumption implies that the eavesdropper has either access to an identity (noiseless) channel or an infinite amount of entanglement in order to simulate such an identity channel. In this work we challenge the necessity of this assumption and we propose a teleportation-based eavesdropping attack, where the eavesdropper is not assumed to have access to the shared channel, that represents the unavoidable noise due to the environment. Under collective measurements, this attack reaches optimality in the limit of an infinite amount of entanglement, while for finite entanglement resources it outperforms the corresponding optimal individual attack. We also calculate the minimum amount of distributed entanglement that is necessary for this eavesdropping scheme, since we consider it as the operationally critical quantity capturing the limitations of a realistic attack. We conclude that the fact that an infinite amount of entanglement is required for an optimal collective eavesdropping attack signifies the robustness of Gaussian quantum key distribution
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