7,263 research outputs found
Teleportation-induced entanglement of two nanomechanical oscillators coupled to a topological superconductor
A one-dimensional topological superconductor features a single fermionic zero
mode that is delocalized over two Majorana bound states located at the ends of
the system. We study a pair of spatially separated nanomechanical oscillators
tunnel-coupled to these Majorana modes. Most interestingly, we demonstrate that
the combination of electron-phonon coupling and a finite charging energy on the
mesoscopic topological superconductor can lead to an effective superexchange
between the oscillators via the non-local fermionic zero mode. We further show
that this teleportation mechanism leads to entanglement of the two oscillators
over distances that can significantly exceed the coherence length of the
superconductor.Comment: 6 page
: A flexible chemical evolution model for abundance fitting - Do the Sun's abundances alone constrain chemical evolution models?
Elemental abundances of stars are the result of the complex enrichment
history of their galaxy. Interpretation of observed abundances requires
flexible modeling tools to explore and quantify the information about Galactic
chemical evolution (GCE) stored in such data. Here we present Chempy, a newly
developed code for GCE modeling, representing a parametrized open one-zone
model within a Bayesian framework. A Chempy model is specified by a set of 5-10
parameters that describe the effective galaxy evolution along with the stellar
and star-formation physics: e.g. the star-formation history, the feedback
efficiency, the stellar initial mass function (IMF) and the incidence of
supernova type Ia (SN Ia). Unlike established approaches, Chempy can sample the
posterior probability distribution in the full model parameter space and test
data-model matches for different nucleosynthetic yield sets. We extend Chempy
to a multi-zone scheme. As an illustrative application, we show that
interesting parameter constraints result from only the ages and elemental
abundances of Sun, Arcturus and the present-day interstellar medium (ISM). For
the first time, we use such information to infer IMF parameter via GCE
modeling, where we properly marginalize over nuisance parameters and account
for different yield sets. We find that of the IMF %
explodes as core-collapse SN, compatible with Salpeter 1955. We also constrain
the incidence of SN Ia per 10^3 Msun to 0.5-1.4. At the same time, this Chempy
application shows persistent discrepancies between predicted and observed
abundances for some elements, irrespective of the chosen yield set. These
cannot be remedied by any variations of Chempy's parameters and could be an
indication for missing nucleosynthetic channels. Chempy should be a powerful
tool to confront predictions from stellar nucleosynthesis with far more complex
abundance data sets.Comment: 19 pages, 17 figures, accepted for publication in A&A, python code:
https://github.com/jan-rybizki/Chemp
Failure of protection of Majorana based qubits against decoherence
Qubit realizations based on Majorana bound states have been considered
promising candidates for quantum information processing which is inherently
inert to decoherence. We put the underlying general arguments leading to this
conjecture to the test from an open quantum system perspective. It turns out
that, from a fundamental point of view, the Majorana qubit is as susceptible to
decoherence as any local paradigm of a qubit.Comment: Published versio
Entanglement of nanoelectromechanical oscillators by Cooper-pair tunneling
We demonstrate that entanglement of two macroscopic nanoelectromechanical
resonators -- coupled to each other via a common detector, a tunnel junction --
can be generated by running a current through the device. We introduce a setup
that overcomes generic limitations of proposals suggesting to entangle systems
via a shared bath. At the heart of the proposal is an Andreev entangler setup,
representing an experimentally feasible way of entangling two nanomechanical
oscillators. Instead of relying on the coherence of a (fermionic) bath, in the
Andreev entangler setup, a split Cooper-pair that coherently tunnels to each
oscillator mediates their coupling and thereby induces entanglement between
them. Since entanglement is in each instance generated by Markovian and
non-Markovian noisy open system dynamics in an out-of-equilibrium situation, we
argue that the present scheme also opens up perspectives to observe
dissipation-driven entanglement in a condensed-matter system.Comment: 11 pages, 3 figure
- …