3,440 research outputs found
Efficient single-photon-assisted entanglement concentration for partially entangled photon pairs
We present two realistic entanglement concentration protocols (ECPs) for pure
partially entangled photons. A partially entangled photon pair can be
concentrated to a maximally entangled pair with only an ancillary single photon
in a certain probability, while the conventional ones require two copies of
partially entangled pairs at least. Our first protocol is implemented with
linear optics and the second one is implemented with cross-Kerr nonlinearities.
Compared with other ECPs, they do not need to know the accurate coefficients of
the initial state. With linear optics, it is feasible with current experiment.
With cross-Kerr nonlinearities, it does not require the sophisticated
single-photon detectors and can be repeated to get a higher success
probability. Moreover, the second protocol can get the higher entanglement
transformation efficiency and it maybe the most economical one by far.
Meanwhile, both of protocols are more suitable for multi-photon system
concentration, because they need less operations and classical communications.
All these advantages make two protocols be useful in current long-distance
quantum communications
Electronic, mechanical, and thermodynamic properties of americium dioxide
By performing density functional theory (DFT) + calculations, we
systematically study the electronic, mechanical, tensile, and thermodynamic
properties of AmO. The experimentally observed antiferromagnetic
insulating feature [J. Chem. Phys. 63, 3174 (1975)] is successfully reproduced.
It is found that the chemical bonding character in AmO is similar to that
in PuO, with smaller charge transfer and stronger covalent interactions
between americium and oxygen atoms. The valence band maximum and conduction
band minimum are contributed by 2 hybridized and 5 electronic states
respectively. The elastic constants and various moduli are calculated, which
show that AmO is less stable against shear forces than PuO. The
stress-strain relationship of AmO is examined along the three low-index
directions by employing the first-principles computational tensile test method.
It is found that similar to PuO, the [100] and [111] directions are the
strongest and weakest tensile directions, respectively, but the theoretical
tensile strengths of AmO are smaller than those of PuO. The phonon
dispersion curves of AmO are calculated and the heat capacities as well
as lattice expansion curve are subsequently determined. The lattice thermal
conductance of AmO is further evaluated and compared with attainable
experiments. Our present work integrally reveals various physical properties of
AmO and can be referenced for technological applications of AmO
based materials.Comment: 23 pages, 8 figure
2-(2-{[2-(2-Pyridylcarbonyl)hydrazono]methyl}phenoxy)acetic acid
In the title compound, C15H13N3O4, the pyridine and benzene rings are nearly coplanar [dihedral angle = 4.92 (12)°]. The maximum deviation from the best least-squares plane calculated for the main molecular skeleton is 0.1722 (1) Å for the carbonyl O atom. In the crystal, intermolecular O—H⋯O hydrogen bonds connect the molecules into a chain, while π–π stacking interactions between the pyridine and benzene rings [centroid–centroid distance = 3.9162 (8) Å and offset angle = 27.20°] complete a two-dimensional network
Diffusion Language Models Can Perform Many Tasks with Scaling and Instruction-Finetuning
The recent surge of generative AI has been fueled by the generative power of
diffusion probabilistic models and the scalable capabilities of large language
models. Despite their potential, it remains elusive whether diffusion language
models can solve general language tasks comparable to their autoregressive
counterparts. This paper demonstrates that scaling diffusion models w.r.t.
data, sizes, and tasks can effectively make them strong language learners. We
build competent diffusion language models at scale by first acquiring knowledge
from massive data via masked language modeling pretraining thanks to their
intrinsic connections. We then reprogram pretrained masked language models into
diffusion language models via diffusive adaptation, wherein task-specific
finetuning and instruction finetuning are explored to unlock their versatility
in solving general language tasks. Experiments show that scaling diffusion
language models consistently improves performance across downstream language
tasks. We further discover that instruction finetuning can elicit zero-shot and
few-shot in-context learning abilities that help tackle many unseen tasks by
following natural language instructions, and show promise in advanced and
challenging abilities such as reasoning.Comment: added reference
Straight-line path following for asymmetric unmanned platform with disturbance estimation
The problem of straight-line path following for asymmetric unmanned platform exposed to unknown disturbances was addressed in this paper. The mathematical model of asymmetric unmanned platform was established and the inputs in sway and yaw directions were decoupled, which facilitated the establishment of control strategy of path following. The guidance law and the cross-track error were derived from the classical line-of-sight (LOS) guidance principle. And the equilibrium point of the cross-track error was proven to be uniformly semiglobally exponentially stable (USGES), which guaranteed the exponential convergence to zero. A new disturbance estimation law was developed by adding a linear item of the estimation error into the classical one, which improved the principle’s precision and sensitivity dramatically. The control strategy was developed based on the integrator backstepping technique and the new disturbance estimation law, which made the equilibrium system to be uniformly globally asymptotically stable (UGAS). Computer simulations were conducted to verify the effectiveness of the estimation and control laws during straight-line path following for asymmetric unmanned platform in the presence of unknown disturbances
Implementing Genuine Multi-Qubit Entanglement of Two-Level-System Inside a Superconducting Phase Qubit
The interaction between a superconducting phase qubit and the two-level
systems locating inside the Josephson tunnel barrier is shown to be described
by the XY model, which is naturally used to implement the iSWAP gate. With this
gate, we propose a scheme to efficiently generate genuine multi-qubit entangled
states of such two-level systems, including multipartite W state and cluster
states. In particularly, we show that, with the help of the phase qubit, the
entanglement witness can be used to efficiently detect the produced genuine
multi-qubit entangled states. Furthermore, we analyze that the proposed
approach for generating multi-qubit entangled states can be used in a wide
class of candidates for quantum computation.Comment: 6 page
Linear Stability of Thick Branes: Tensor Perturbations
We explore thick branes in gravity. We obtain the linear tensor
perturbation equation of branes and show that the branes are
stable against the tensor perturbations under the condition of . In order to obtain thick brane solutions of the
fourth-order field equations in this theory, we employ the reconstruction
technique. We get exact solutions of the specific thick brane
generated by a non-canonical scalar field. It is shown that the zero mode of
the graviton for the thick brane is localized under certain conditions. This
implies that the four-dimensional Newtonian potential is recovered on the
brane. The effects of the Kaluza-Klein modes of the graviton for the
thick brane are also discussed.Comment: 23 pages, 5 figure
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