5,914 research outputs found
Enhanced No-Go Theorem for Quantum Position Verification
Based on the instantaneous nonlocal quantum computation (INQC), Buhrman et
al. proposed an excellent attack strategy to quantum position verification
(QPV) protocols in 2011, and showed that, if the colluding adversaries are
allowed to previously share unlimited entangled states, it is impossible to
design an unconditionally secure QPV protocol in the previous model. Here,
trying to overcome this no-go theorem, we find some assumptions in the INQC
attack, which are implicit but essential for the success of this attack, and
present three different QPV protocols where these assumptions are not
satisfied. We show that for the general adversaries, who execute the attack
operations at every common time slot or the time when they detect the arrival
of the challenge signals from the verifiers, secure QPV is achievable. This
implies practically secure QPV can be obtained even if the adversaries is
allowed to share unlimited entanglement previously. Here by "practically" we
mean that in a successful attack the adversaries need launch a new round of
attack on the coming qubits with extremely high frequency so that none of the
possible qubits, which may be sent at random time, will be missed. On the other
side, using such Superdense INQC (SINQC) attack, the adversaries can still
attack the proposed protocols successfully in theory. The particular attack
strategies to our protocols are presented respectively. On this basis, we
demonstrate the impossibility of secure QPV with looser assumptions, i.e. the
enhanced no-go theorem for QPV.Comment: 19 pages, single column, 3 tables, 6 figure
PocketCare: Tracking the Flu with Mobile Phones using Partial Observations of Proximity and Symptoms
Mobile phones provide a powerful sensing platform that researchers may adopt
to understand proximity interactions among people and the diffusion, through
these interactions, of diseases, behaviors, and opinions. However, it remains a
challenge to track the proximity-based interactions of a whole community and
then model the social diffusion of diseases and behaviors starting from the
observations of a small fraction of the volunteer population. In this paper, we
propose a novel approach that tries to connect together these sparse
observations using a model of how individuals interact with each other and how
social interactions happen in terms of a sequence of proximity interactions. We
apply our approach to track the spreading of flu in the spatial-proximity
network of a 3000-people university campus by mobilizing 300 volunteers from
this population to monitor nearby mobile phones through Bluetooth scanning and
to daily report flu symptoms about and around them. Our aim is to predict the
likelihood for an individual to get flu based on how often her/his daily
routine intersects with those of the volunteers. Thus, we use the daily
routines of the volunteers to build a model of the volunteers as well as of the
non-volunteers. Our results show that we can predict flu infection two weeks
ahead of time with an average precision from 0.24 to 0.35 depending on the
amount of information. This precision is six to nine times higher than with a
random guess model. At the population level, we can predict infectious
population in a two-week window with an r-squared value of 0.95 (a random-guess
model obtains an r-squared value of 0.2). These results point to an innovative
approach for tracking individuals who have interacted with people showing
symptoms, allowing us to warn those in danger of infection and to inform health
researchers about the progression of contact-induced diseases
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