73,981 research outputs found
Optimized Double-well quantum interferometry with Gaussian squeezed-states
A Mach-Zender interferometer with a gaussian number-difference squeezed input
state can exhibit sub-shot-noise phase resolution over a large phase-interval.
We obtain the optimal level of squeezing for a given phase-interval
and particle number , with the resulting phase-estimation
uncertainty smoothly approaching as approaches 10/N,
achieved with highly squeezed states near the Fock regime. We then analyze an
adaptive measurement scheme which allows any phase on to be
measured with a precision of requiring only a few measurements, even
for very large . We obtain an asymptotic scaling law of , resulting in a final
precision of . This scheme can be readily implemented in a
double-well Bose-Einstein condensate system, as the optimal input states can be
obtained by adiabatic manipulation of the double-well ground state.Comment: updated versio
Electroweak Baryogenesis with dimension-6 Higgs interactions
We present the computation of the baryon asymmetry in the SM amplified by
dimension-6 Higgs interactions using the WKB approximation. Analyzing the
one-loop potential it turns out that the phase transition is strongly first
order in a wide range of the parameters. It is ensured not to wash out the net
baryon number gained previously even for Higgs masses up to at least 170 GeV.
In addition dimension-6 operators induce new sources of CP violation. Novel
source terms which enhance the generated baryon asymmetry emerge in the
transport equations. This model predicts a baryon to entropy ratio close to the
observed value for a large part of the parameter space.Comment: 10 pages, 4 figures, Talk given at the 8th International Moscow
School of Physic
Reinforcement Learning: A Survey
This paper surveys the field of reinforcement learning from a
computer-science perspective. It is written to be accessible to researchers
familiar with machine learning. Both the historical basis of the field and a
broad selection of current work are summarized. Reinforcement learning is the
problem faced by an agent that learns behavior through trial-and-error
interactions with a dynamic environment. The work described here has a
resemblance to work in psychology, but differs considerably in the details and
in the use of the word ``reinforcement.'' The paper discusses central issues of
reinforcement learning, including trading off exploration and exploitation,
establishing the foundations of the field via Markov decision theory, learning
from delayed reinforcement, constructing empirical models to accelerate
learning, making use of generalization and hierarchy, and coping with hidden
state. It concludes with a survey of some implemented systems and an assessment
of the practical utility of current methods for reinforcement learning.Comment: See http://www.jair.org/ for any accompanying file
On-demand generation of entanglement of atomic qubits via optical interferometry
The problem of on-demand generation of entanglement between single-atom
qubits via a common photonic channel is examined within the framework of
optical interferometry. As expected, for a Mach-Zehnder interferometer with
coherent laser beam as input, a high-finesse optical cavity is required to
overcome sensitivity to spontaneous emission. We show, however, that with a
twin-Fock input, useful entanglement can in principle be created without
cavity-enhancement. Both approaches require single-photon resolving detectors,
and best results would be obtained by combining both cavity-feedback and
twin-Fock inputs. Such an approach may allow a fidelity of using a
two-photon input and currently available mirror and detector technology. In
addition, we study interferometers based on NOON states and show that they
perform similarly to the twin-Fock states, yet without the need for
high-precision photo-detectors. The present interferometrical approach can
serve as a universal, scalable circuit element for quantum information
processing, from which fast quantum gates, deterministic teleportation,
entanglement swapping , can be realized with the aid of single-qubit
operations.Comment: To be published in PR
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