28,825 research outputs found
An All-But-One Entropic Uncertainty Relation, and Application to Password-based Identification
Entropic uncertainty relations are quantitative characterizations of
Heisenberg's uncertainty principle, which make use of an entropy measure to
quantify uncertainty. In quantum cryptography, they are often used as
convenient tools in security proofs. We propose a new entropic uncertainty
relation. It is the first such uncertainty relation that lower bounds the
uncertainty in the measurement outcome for all but one choice for the
measurement from an arbitrarily large (but specifically chosen) set of possible
measurements, and, at the same time, uses the min-entropy as entropy measure,
rather than the Shannon entropy. This makes it especially suited for quantum
cryptography. As application, we propose a new quantum identification scheme in
the bounded quantum storage model. It makes use of our new uncertainty relation
at the core of its security proof. In contrast to the original quantum
identification scheme proposed by Damg{\aa}rd et al., our new scheme also
offers some security in case the bounded quantum storage assumption fails hold.
Specifically, our scheme remains secure against an adversary that has unbounded
storage capabilities but is restricted to non-adaptive single-qubit operations.
The scheme by Damg{\aa}rd et al., on the other hand, completely breaks down
under such an attack.Comment: 33 pages, v
Biasing in Gaussian random fields and galaxy correlations
In this letter we show that in a Gaussian random field the correlation
length, the typical size of correlated structures, does not change with
biasing. We interpret the amplification of the correlation functions of subsets
identified by different thresholds being due to the increasing sparseness of
peaks over threshold. This clarifies an long-standing misconception in the
literature. We also argue that this effect does not explain the observed
increase of the amplitude of the correlation function xi(r) when galaxies of
brighter luminosity or galaxy clusters of increasing richness are considered.Comment: 16 pages, 3 figures, minor changes and corrected some typos to match
the version in Astrophysical Journal Letters (2000
A 10-bit Charge-Redistribution ADC Consuming 1.9 μW at 1 MS/s
This paper presents a 10 bit successive approximation ADC in 65 nm CMOS that benefits from technology scaling. It meets extremely low power requirements by using a charge-redistribution DAC that uses step-wise charging, a dynamic two-stage comparator and a delay-line-based controller. The ADC requires no external reference current and uses only one external supply voltage of 1.0 V to 1.3 V. Its supply current is proportional to the sample rate (only dynamic power consumption). The ADC uses a chip area of approximately 115--225 μm2. At a sample rate of 1 MS/s and a supply voltage of 1.0 V, the 10 bit ADC consumes 1.9 μW and achieves an energy efficiency of 4.4 fJ/conversion-step
Generation of Motion of Drops with Interfacial Contact
A liquid drop moves on a solid surface if it is subjected to a gradient of
wettability or temperature. However, the pinning defects on the surface
manifested in terms of a wetting hysteresis, or first-order nonlinear friction,
limit the motion in the sense that a critical size has to be exceeded for a
drop to move. The effect of hysteresis can, however, be mitigated by an
external vibration that can be either structured or stochastic, thereby
creating a directed motion of the drop. Many of the well-known features of
rectification, amplification, and switching that are generic to electronics can
be engineered with such types of movements. A specific case of interest is the
random coalescence of drops on a surface that gives rise to self-generated
noise. This noise overcomes the pinning potential, thereby generating a random
motion of the coalesced drops. Randomly moving coalesced drops themselves
exhibit a directed diffusive flux when a boundary is present to eliminate them
by absorption. With the presence of a bias, the coalesced drops execute a
diffusive drift motion that can have useful applications in various water and
thermal management technologies
A Survey for Large Separation Lensed FIRST Quasars
Little is known about the statistics of gravitationally lensed quasars at
large (7''-30'') image separations, which probe masses on the scale of galaxy
clusters. We have carried out a survey for gravitationally-lensed objects,
among sources in the FIRST 20cm radio survey that have unresolved optical
counterparts in the digitizations of the Palomar Observatory Sky Survey. From
the statistics of ongoing surveys that search for quasars among FIRST sources,
we estimate that there are about 9100 quasars in this source sample, making
this one of the largest lensing surveys to date. Using broad-band imaging, we
have isolated all objects with double radio components separated by 5''-30'',
that have unresolved optical counterparts with similar BVI colours. Our
criteria for similar colours conservatively allow for observational error and
for colour variations due to time delays between lensed images. Spectroscopy of
these candidates shows that none of the pairs are lensed quasars. This sets an
upper limit (95% confidence) on the lensing fraction in this survey of
3.3x10^-4, assuming 9100 quasars. Although the source redshift distribution is
poorly known, a rough calculation of the expected lensing frequency and the
detection efficiencies and biases suggests that simple theoretical expectations
are of the same order of magnitude as our observational upper limit. Our
procedure is novel in that our exhaustive search for lensed objects does not
require prior identification of the quasars in the sample as such.
Characterization of the FIRST-selected quasar population will enable using our
result to constrain quantitatively the mass properties of clusters.Comment: 10 pages, accepted for publication in MNRA
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