8,867 research outputs found
Increasing and decreasing entanglement characteristics for continuous variables by a local photon subtraction
We investigate how the entanglement characteristics of a non-Gaussian
entangled state are increased or decreased by a local photon subtraction
operation. The non-Gaussian entangled state is generated by injecting a
single-mode non-Gaussian state and a vacuum state into a 50:50 beam splitter.
We consider a photon-added coherent state and an odd coherent state as a
single-mode non-Gaussian state. In the regime of small amplitude, we show that
the performance of quantum teleportation and the second-order
Einstein-Podolsky- Rosen-type correlation can both be enhanced, whereas the
degree of entanglement decreases, for the output state when a local photon
subtraction operation is applied to the non-Gaussian entangled state. The
counterintuitive effect is more prominent in the limit of nearly zero
amplitude.Comment: Published version, 7 pages, 3 figure
Enhancing quantum entanglement for continuous variables by a coherent superposition of photon subtraction and addition
We investigate how the entanglement properties of a two-mode state can be
improved by performing a coherent superposition operation of photon subtraction
and addition, proposed by Lee and Nha [Phys. Rev. A 82, 053812 (2010)], on each
mode. We show that the degree of entanglement, the EPR-type correlation, and
the performance of quantum teleportation can be all enhanced for the output
state when the coherent operation is applied to a two-mode squeezed state. The
effects of the coherent operation are more prominent than those of the mere
photon subtraction and the addition particularly in the small squeezing regime,
whereas the optimal operation becomes the photon subtraction in the
large-squeezing regime.Comment: 6 pages, 6 figures, published versio
Predicting the Configuration of Planetary System: KOI-152 Observed by Kepler
The recent Kepler discovery of KOI-152 reveals a system of three hot
super-Earth candidates that are in or near a 4:2:1 mean motion resonance. It is
unlikely that they formed in situ, the planets probably underwent orbital
migration during the formation and evolution process. The small semimajor axes
of the three planets suggest that migration stopped at the inner edge of the
primordial gas disk. In this paper we focus on the influence of migration
halting mechanisms, including migration "dead zones", and inner truncation by
the stellar magnetic field. We show that the stellar accretion rate, stellar
magnetic field and the speed of migration in the proto-planetary disk are the
main factors affecting the final configuration of KOI-152. Our simulations
suggest that three planets may be around a star with low star accretion rate or
with high magnetic field. On the other hand, slow type I migration, which
decreases to one tenth of the linear analysis results, favors forming the
configuration of KOI-152. Under such formation scenario, the planets in the
system are not massive enough to open gaps in the gas disk. The upper limit of
the planetary masses are estimated to be about , and ,
respectively. Our results are also indicative of the near Laplacian
configurations that are quite common in planetary systems.Comment: 11 pages, 8 figures, accepted for publication in Ap
Quantum linear amplifier enhanced by photon subtraction and addition
A deterministic quantum amplifier inevitably adds noise to an amplified
signal due to the uncertainty principle in quantum physics. We here investigate
how a quantum-noise-limited amplifier can be improved by additionally employing
the photon subtraction, the photon addition, and a coherent superposition of
the two, thereby making a probabilistic, heralded, quantum amplifier. We show
that these operations can enhance the performance in amplifying a coherent
state in terms of intensity gain, fidelity, and phase uncertainty. In
particular, the photon subtraction turns out to be optimal for the fidelity and
the phase concentration among these elementary operations, while the photon
addition also provides a significant reduction in the phase uncertainty with
the largest gain effect.Comment: published version, 7 pages, 9 figure
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