The European Physical Journal D最新文献

Solar physicists routinely utilize observations of Ar-like Fe IX and Cl-like Fe X emission to study a variety of solar structures. However, unidentified lines exist in the Fe IX and Fe X spectra, greatly impeding the spectroscopic diagnostic potential of these ions. Here, we present measurements using the Lawrence Livermore National Laboratory EBIT-I electron beam ion trap in the wavelength range 238–258 Å. These studies enable us to unambiguously identify the charge state associated with each of the observed lines. This wavelength range is of particular interest because it contains the Fe IX density diagnostic line ratio 241.74 Å/244.91 Å, which is predicted to be one of the best density diagnostics of the solar corona, as well as the Fe X 257.26 Å magnetic-field-induced transition. We compare our measurements to the Fe IX and Fe X lines tabulated in CHIANTI v10.0.1, which is used for modeling the solar spectrum. In addition, we have measured previously unidentified Fe X lines that will need to be added to CHIANTI and other spectroscopic databases.

We present a two-state Kalman estimator of gravity acceleration and evaluate its performance by numerical simulations and post-measurement demonstration with real-world atomic gravimetry. We show that the estimator-enhanced gravimetry significantly improves upon both short-term sensitivity and long-term stability. The estimates of gravity acceleration demonstrate a (tau ^{1/2}) feature well under white phase noise in the short term, and continue to improve as (tau ^{-1/2}) or improve faster as (tau ^{-1}) in the long term. This work validates the estimation of gravity acceleration as a key topic for future atomic gravimetry.

The performance of atomic gravimetry is limited by noises and other systematic or geophysical effects. By building a Kaman estimator rooted in the physics of atom interferometry, we realize significant improvements in both short-term sensitivity and long-term stability. This demonstration of estimator-enhanced gravimetry would be of great interest for static measurements of gravity, such as metrology or geophysics (Color online)

Creating non-Gaussian photonic states in the continuous variable regime, with high fidelity is essential for implementing universal quantum computation. However, this is a challenging task to achieve the essential nonlinearity. Alternatively, various non-Gaussian states of light can be created by the use of a simple linear setup called quantum optical catalysis (QOC). In this work, we attempt to bring out the salient features of the multi-photon QOC process in terms of state preparation and characterization. The notion of state preparation from the QOC is achieved by expressing the output state as displaced qudits (DQ). The obtained superposition coefficients facilitate the characterization of states and carve a path to get desired non-Gaussian states. Moreover, the figures of merit of the prepared states are employed through Hilbert Schmidt distance, Wigner negativity, and quadrature squeezing. From the results, it is inferred that the creation of individual displaced number states plays a predominant role in non-Gaussianity among the states derived. Meanwhile, the superposition of number states remains effective in achieving a significant degree of squeezing. In addition, the non-ideal preparation of DQ under realistic experimental conditions is investigated by incorporating imperfect photon detectors and mixed photon sources. The calculated success probability also attests to the potential for state generation.

In quantum phase estimation, the Heisenberg limit provides the ultimate accuracy over quasi-classical estimation procedures. However, realizing this limit hinges upon both the detection strategy employed for output measurements and the characteristics of the input states. This study delves into quantum phase estimation using s-spin coherent states superposition. Initially, we delve into the explicit formulation of spin coherent states for a spin (s=3/2). Both the quantum Fisher information and the quantum Cramer–Rao bound are meticulously examined. We analytically show that the ultimate measurement precision of spin cat states approaches the Heisenberg limit, where uncertainty decreases inversely with the total particle number. Moreover, we investigate the phase sensitivity introduced through operators (e^{izeta {S}_{z}}), (e^{izeta {S}_{x}}) and (e^{izeta {S}_{y}}), subsequently comparing the resultants findings. In closing, we provide a general analytical expression for the quantum Cramér–Rao bound applied to these three parameter-generating operators, utilizing general s-spin coherent states. We remarked that attaining Heisenberg-limit precision requires the careful adjustment of insightful information about the geometry of s-spin cat states on the Bloch sphere. Additionally, as the number of s-spin increases, the Heisenberg limit decreases, and this reduction is inversely proportional to the s-spin number.

The effects of absorption and saturation on soliton states in Kerr-type nonlinear layers are theoretically investigated. In addition to the usual gray and bright soliton structures observed in nonlinear slabs, a flat soliton, i.e., a particular soliton excitation with electric field amplitude independent of the position within the layer, is researched in cases of self-defocusing and self-focusing nonlinearities. Effects caused by the combination of absorption and saturation, such as the shift and extinction of the flat soliton peak, the decrease in the amplitude of the electric field within the nonlinear layer, and the suppression of the multistable behavior of the transmission coefficient in the vicinity of the soliton peaks, are discussed. The present theoretical results are compared and found in good quantitative agreement with previous experimental measurements.

We present a progress report on the development of PyXstar, a Python package to manage the data (input, output, intermediate, atomic database, and model-grids) associated with the xstar code for treating photoionized and collisionally ionized plasmas. The PyXstar modular structure and database retrieval scheme are described, and its functionality is illustrated with Python functions and classes for performing database searches. We briefly compare PyXstar with two other Python spectrum modeling tools: PyNeb and PyAtomDB.

The existing notion of the shared entangled state-assisted remote preparation of unitary operator (equivalently the existing notion of quantum remote control) using local operation and classical communication is generalized to a scenario where under the control of a supervisor two users can jointly implement arbitrary unitaries (one unknown unitary operation by each or equivalently a single unitary decomposed into two unitaries of the same dimension and given to two users) on an unknown quantum state available with a geographically separated user. It is explicitly shown that the task can be performed using a four-qubit hyperentangled state, which is entangled simultaneously in both spatial and polarization degrees of freedom of photons. The proposed protocol which can be viewed as primitive for distributed photonic quantum computing is further generalized to the case that drops the restrictions on the number of controllers and the number of parties performing unitaries and allows both the numbers to be arbitrary. It is also shown that all the existing variants of quantum remote control schemes can be obtained as special cases of the present scheme.