10,175 research outputs found
Magnetic structures of Mn3-xFexSn2: an experimental and theoretical study
We investigate the magnetic structure of Mn3-xFexSn2 using neutron powder
diffraction experiments and electronic structure calculations. These alloys
crystallize in the orthorhombic Ni3Sn2 type of structure (Pnma) and comprise
two inequivalent sites for the transition metal atoms (4c and 8d) and two Sn
sites (4c and 4c). The neutron data show that the substituting Fe atoms
predominantly occupy the 4c transition metal site and carry a lower magnetic
moment than Mn atoms. Four kinds of magnetic structures are encountered as a
function of temperature and composition: two simple ferromagnetic structures
(with the magnetic moments pointing along the b or c axis) and two canted
ferromagnetic arrangements (with the ferromagnetic component pointing along the
b or c axis). Electronic structure calculations results agree well with the
low-temperature experimental magnetic moments and canting angles throughout the
series. Comparisons between collinear and non-collinear computations show that
the canted state is stabilized by a band mechanism through the opening of a
hybridization gap. Synchrotron powder diffraction experiments on Mn3Sn2 reveal
a weak monoclinic distortion at low temperature (90.08 deg at 175 K). This
lowering of symmetry could explain the stabilization of the c-axis canted
ferromagnetic structure, which mixes two orthorhombic magnetic space groups, a
circumstance that would otherwise require unusually large high-order terms in
the spin Hamiltonian.Comment: 11 pages, 13 figure
Valence Compounds versus Metals. Synthesis, Characterization, and Electronic Structures of Cubic Ae4Pn3 Phases in the Systems Ae = Ca, Sr, Ba, Eu; Pn = As, Sb, Bi
The isostructural compounds Sr4Bi3, Ba4Bi3, and Ba4As∼2.60 were prepared by direct reactions of the corresponding elements and their structures determined from single-crystal X-ray diffraction data as anti-Th3P4 type in the cubic space group I4̄3d, Z = 4 (a = 10.101(1) Å, 10.550(1) Å, 9.973 (1) Å, respectively). The two bismuth compounds are stoichiometric, and the arsenide refines as Ba4As2.60(2). Only unrelated phases are obtained for all binary combinations among the title components for either Ca or Sb. The magnetic susceptibility and resistivities of Ba4Bi3 and Eu4Bi3 show that they are good metallic conductors (∼40 μΩ·cm at 298 K), whereas Ba4As2.60 exhibits ρ150 \u3e 1000 μΩ·cm. The electronic structures of Sr4Bi3, Ba4Bi3, and Ba4As3 were calculated by TB-LMTO-ASA methods. Mixing of cation d states into somewhat disperse valence p bands on Bi results in empty bands at EF and metallic behavior, whereas the narrower valence band in the electron-deficient Ba4As3 leads to vacancies in about 11% of the anion sites and a valence compound
Entanglement dynamics of bipartite system in squeezed vacuum reservoirs
Entanglement plays a crucial role in quantum information protocols, thus the
dynamical behavior of entangled states is of a great importance. In this paper
we suggest a useful scheme that permits a direct measure of entanglement in a
two-qubit cavity system. It is realized in the cavity-QED technology utilizing
atoms as fying qubits. To quantify entanglement we use the concurrence. We
derive the conditions, which assure that the state remains entangled in spite
of the interaction with the reservoir. The phenomenon of sudden death
entanglement (ESD) in a bipartite system subjected to squeezed vacuum reservoir
is examined. We show that the sudden death time of the entangled states depends
on the initial preparation of the entangled state and the parameters of the
squeezed vacuum reservoir.Comment: 10 pages, 5 figures, CEWQO17(St Andrews
Optimizing edge state transfer in a Su-Schrieffer-Heeger chain via hybrid digital-analog strategies
Su-Schrieffer-Heeger (SSH) chain, serving as a paradigmatic model for
comprehending topological phases and their associated edge states, plays a
pivotal role in advancing our understanding of quantum materials and quantum
information processing and technology. In this paper, we introduce a hybrid
analog-digital protocol designed for the non-adiabatic yet high-fidelity
transfer of edge states in a SSH chain, featuring two sublattices A and B. The
core of our approach lies in harnessing the approximate time-dependent
counter-diabatic (CD) interaction, derived from adiabatic gauge potentials.
However, to enhance transfer fidelity, particularly in long-distance chains,
higher-order nested commutators become crucial. To simplify experimental
implementation and navigate computational complexities, we identify the
next-to-nearest-neighbour (NNN) hopping terms between sublattice A as dominant
CD drivings, and further optimize them by using variational quantum circuits.
Through digital quantum simulation, our protocol showcases the capability to
achieve rapid and robust solutions, even in the presence of disorder. This
analog-digital transfer protocol, an extension of quantum control methodology,
establishes a robust framework for edge state transfer. Importantly, the
optimal CD drivings identified can be seamlessly implemented across various
quantum registers, highlighting the versatility of our approach
Unified Treatment of Heterodyne Detection: the Shapiro-Wagner and Caves Frameworks
A comparative study is performed on two heterodyne systems of photon
detectors expressed in terms of a signal annihilation operator and an image
band creation operator called Shapiro-Wagner and Caves' frame, respectively.
This approach is based on the introduction of a convenient operator
which allows a unified formulation of both cases. For the Shapiro-Wagner
scheme, where , quantum phase and amplitude
are exactly defined in the context of relative number state (RNS)
representation, while a procedure is devised to handle suitably and in a
consistent way Caves' framework, characterized by , within the approximate simultaneous measurements of
noncommuting variables. In such a case RNS phase and amplitude make sense only
approximately.Comment: 25 pages. Just very minor editorial cosmetic change
Conceptualizing throughput legitimacy: procedural mechanisms of accountability, transparency, inclusiveness and openness in EU governance
This symposium demonstrates the potential for throughput legitimacy as a concept for shedding empirical light on the strengths and weaknesses of multi-level governance, as well as challenging the concept theoretically. This article introduces the symposium by conceptualizing throughput legitimacy as an ‘umbrella concept’, encompassing a constellation
of normative criteria not necessarily empirically interrelated. It argues that in order to interrogate multi-level governance processes in all their complexity, it makes sense for us to develop normative standards that are not naïve about the empirical realities of how power is exercised within multilevel governance, or how it may interact with legitimacy. We argue that while throughput legitimacy has its normative limits, it can be substantively useful for these purposes. While being no replacement for input and output legitimacy, throughput legitimacy offers distinctive normative criteria— accountability, transparency, inclusiveness and openness— and points towards substantive institutional reforms.Published versio
Densovirus induces winged morphs in asexual clones of the rosy apple aphid, Dysaphis plantaginea
Winged morphs of aphids are essential for their dispersal and survival. We discovered that the production of the winged morph in asexual clones of the rosy apple aphid, Dysaphis plantaginea, is dependent on their infection with a DNA virus, Dysaphis plantaginea densovirus (DplDNV). Virus-free clones of the rosy apple aphid, or clones infected singly with an RNA virus, rosy apple aphid virus (RAAV), did not produce the winged morph in response to crowding and poor plant quality. DplDNV infection results in a significant reduction in aphid reproduction rate, but such aphids can produce the winged morph, even at low insect density, which can fly and colonize neighboring plants. Aphids infected with DplDNV produce a proportion of virus-free aphids, which enables production of virus-free clonal lines after colonization of a new plant. Our data suggest that a mutualistic relationship exists between the rosy apple aphid and its viruses. Despite the negative impact of DplDNV on rosy apple aphid reproduction, this virus contributes to their survival by inducing wing development and promoting dispersal
Hybrid Approach for Solving Real-World Bin Packing Problem Instances Using Quantum Annealers
Efficient packing of items into bins is a common daily task. Known as Bin
Packing Problem, it has been intensively studied in the field of artificial
intelligence, thanks to the wide interest from industry and logistics. Since
decades, many variants have been proposed, with the three-dimensional Bin
Packing Problem as the closest one to real-world use cases. We introduce a
hybrid quantum-classical framework for solving real-world three-dimensional Bin
Packing Problems (Q4RealBPP), considering different realistic characteristics,
such as: i) package and bin dimensions, ii) overweight restrictions, iii)
affinities among item categories and iv) preferences for item ordering.
Q4RealBPP permits the solving of real-world oriented instances of 3dBPP,
contemplating restrictions well appreciated by industrial and logistics
sectors.Comment: 9 pages, 24 figure
Testing in various samples of the efficacy of counters with the same calibration
Da bi se mogli iskoristiti svi brojači za razne vrste uzoraka, provjerena je efikasnost GM brojača raznih konstrukcija pri istovetnoj kalibraciji.The samples of various activities and various degrees of energy were tested with a 5 % counting error by the counters of various construction whose efficacy was determined by means of the K-40 standard. The activities of the samples, corrected to the back ground and efficacy, were tested by the method of variance. The 0-hypothesis is accepted, which means that the differences in the activities registered by all the counters were not statistically significant
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