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Plethodon ouachitae
Number of Pages: 2Integrative BiologyGeological Science
Waiting times of entangled electrons in normal-superconducting junctions
We consider a normal-superconducting junction in order to investigate the
effect of new physical ingredients on waiting times. First, we study the
interplay between Andreev and specular scattering at the interface on the
distribution of waiting times of electrons or holes separately. In that case
the distribution is not altered dramatically compared to the case of a single
quantum channel with a quantum point contact since the interface acts as an
Andreev mirror for holes. We then consider a fully entangled state originating
from spliting of Cooper pairs at the interface and demonstrate a significant
enhancement of the probability to detect two consecutive electrons in a short
time interval. Finally, we discuss the electronic waiting time distribution in
the more realistic situation of partial entanglement
Overcoming loss of contrast in atom interferometry due to gravity gradients
Long-time atom interferometry is instrumental to various high-precision
measurements of fundamental physical properties, including tests of the
equivalence principle. Due to rotations and gravity gradients, the classical
trajectories characterizing the motion of the wave packets for the two branches
of the interferometer do not close in phase space, an effect which increases
significantly with the interferometer time. The relative displacement between
the interfering wave packets in such open interferometers leads to a fringe
pattern in the density profile at each exit port and a loss of contrast in the
oscillations of the integrated particle number as a function of the phase
shift. Paying particular attention to gravity gradients, we present a simple
mitigation strategy involving small changes in the timing of the laser pulses
which is very easy to implement. A useful representation-free description of
the state evolution in an atom interferometer is introduced and employed to
analyze the loss of contrast and mitigation strategy in the general case. (As a
by-product, a remarkably compact derivation of the phase-shift in a general
light-pulse atom interferometer is provided.) Furthermore, exact results are
obtained for (pure and mixed) Gaussian states which allow a simple
interpretation in terms of the alignment of Wigner functions in phase-space.
Analytical results are also obtained for expanding Bose-Einstein condensates
within the time-dependent Thomas-Fermi approximation. Finally, a combined
strategy for rotations and nonaligned gravity gradients is considered as well.Comment: 14+7 pages including appendices, 9 figures; v2 minor changes, matches
published versio
What is the Role of Recurrent Neural Networks (RNNs) in an Image Caption Generator?
In neural image captioning systems, a recurrent neural network (RNN) is
typically viewed as the primary `generation' component. This view suggests that
the image features should be `injected' into the RNN. This is in fact the
dominant view in the literature. Alternatively, the RNN can instead be viewed
as only encoding the previously generated words. This view suggests that the
RNN should only be used to encode linguistic features and that only the final
representation should be `merged' with the image features at a later stage.
This paper compares these two architectures. We find that, in general, late
merging outperforms injection, suggesting that RNNs are better viewed as
encoders, rather than generators.Comment: Appears in: Proceedings of the 10th International Conference on
Natural Language Generation (INLG'17
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