Ultracoherent operation of spin qubits with superexchange coupling. With the use of nuclear-spin-free materials such as silicon and germanium, spin-based quantum bits qubits have evolved to become among the most coherent systems for quantum information processing. The new frontier for spin qubits has therefore shifted to the ubiquitous charge noise and spin-orbit interaction, which are limiting the coherence times and gate fidelities of solid-state qubits. In this paper we investigate superexchange , as a means of indirect exchange interaction between two single electron spin qubits, each embedded in a single semiconductor quantum dot QD , mediated by an intermediate, empty QD. Our results suggest the existence of "supersweet spots", in which the qubit operations implemented by superexchange interaction are simultaneously first-order-insensitive to charge noise and to errors due to spin-orbit interaction. The proposed spin-qubit architecture is scalable and within the manufacturing capabilities of semiconductor industry.
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Ultracoherent operation of spin qubits with superexchange coupling. With the use of nuclear-spin-free materials such as silicon and germanium, spin-based quantum bits qubits have evolved to become among the most coherent systems for quantum information processing. The new frontier for spin qubits has therefore shifted to the ubiquitous charge noise and spin-orbit interaction, which are limiting the coherence times and gate fidelities of solid-state qubits. In this paper we investigate superexchange , as a means of indirect exchange interaction between two single electron spin qubits, each embedded in a single semiconductor quantum dot QD , mediated by an intermediate, empty QD.
Our results suggest the existence of "supersweet spots", in which the qubit operations implemented by superexchange interaction are simultaneously first-order-insensitive to charge noise and to errors due to spin-orbit interaction.
The proposed spin-qubit architecture is scalable and within the manufacturing capabilities of semiconductor industry. Superexchange and spin-glass formation in semimagnetic semiconductors. In the present work, the function f r is obtained analytically. This, only weakly material-dependent function is found to decrease with Mn-Mn distance much slower than its Gaussian approximation derived previously.
The exact form of the decay of the superexchange can be approximated by a power law J0r This is close to an experimental result, J0r Effect of orbital symmetry on the anisotropic superexchange interaction. Employing the microscopic superexchange model incorporating the effect of spin-orbit interaction, we have investigated the Dzyaloshinsky-Moriya DM interaction in perovskite transition-metal TM oxides and explored the interplay between the DM interaction and the TM-3d orbital symmetry.
For d 3 and d 5 systems with isotropic orbital symmetry, the DM vectors are well described by a simple symmetry analysis considering only the bond geometry. In contrast, the DM interaction for d 4 systems with anisotropic orbital symmetry shows slightly different behavior, which does not obey simple symmetry analysis.
The direction as well as the strength of the DM vector varies depending on the occupied orbital shape. We have understood this behavior based on the orbital symmetry induced by local crystal field variation.
CI Implementation. There are a number of tools available for organizations wishing to measure and subsequently develop Continuous Improvement CI. In this article, we review and evaluate a well-accepted CI development model, namely the CI Maturity Model Bessant and Caffyn, , against data collected from the 2nd Continuous Improvement Network Survey and a number of empirical cases described in the literature.
While the CI Maturity Model suggests that CI maturation ought to be a linear process, the findings in this article suggest that there are feasible alternatives for companies to develop CI capability Monte Carlo study of the double and super-exchange model with lattice distortion.
Mexico ; Avignon, M, E-mail: jrsuarez iim. In this work a magneto-elastic phase transition was obtained in a linear chain due to the interplay between magnetism and lattice distortion in a double and super-exchange model. It is considered a linear chain consisting of localized classical spins interacting with itinerant electrons. Due to the double exchange interaction, localized spins tend to align ferromagnetically. This ferromagnetic tendency is expected to be frustrated by anti-ferromagnetic super-exchange interactions between neighbor localized spins.
Additionally, lattice parameter is allowed to have small changes, which contributes harmonically to the energy of the system. Phase diagram is obtained as a function of the electron density and the super-exchange interaction using a Monte Carlo minimization. At low super-exchange interaction energy phase transition between electron-full ferromagnetic distorted and electron-empty anti-ferromagnetic undistorted phases occurs. In this case all electrons and lattice distortions were found within the ferromagnetic domain.
For high super-exchange interaction energy, phase transition between two site distorted periodic arrangement of independent magnetic polarons ordered anti-ferromagnetically and the electron-empty anti-ferromagnetic undistorted phase was found. For this high interaction energy, Wigner crystallization, lattice distortion and charge distribution inside two-site polarons were obtained. Double and super-exchange model in one-dimensional systems. We present an analytical and numerical study of the competition between double and super-exchange interactions in a one-dimensional model.
For low super-exchange interaction energy we find phase separation between ferromagnetic and anti-ferromagnetic phases. When the super-exchange interaction energy gets larger, the conduction electrons are self-trapped within separate small magnetic polarons.
These magnetic polarons contain a single electron inside two or three sites depending on the conduction electron density and form a Wigner crystallization. A new phase separation is found between these small polarons and the anti-ferromagnetic phase. Spin-glass behavior is obtained consistent with experimental results of the nickelate one-dimensional compound Y 2-x Ca x BaNiO 5.
CERN Multimedia. The Swiss Permanent Mission to the International Organisations at Geneva recalls that only the spouses and children of members of personnel resident in Switzerland and in possession of a legitimation card of types 'B', 'C', 'D' or 'E' issued by the Swiss Federal Department of Foreign Affairs are entitled to benefit from a Ci Permit.
Ukaegbe, CI. ISSN: Large-amplitude superexchange of high-spin fermions in optical lattices. We show that fermionic high-spin systems with spin-changing collisions allow one to monitor superexchange processes in optical superlattices with large amplitudes and strong spin fluctuations. By investigating the non-equilibrium dynamics, we find a superexchange dominated regime at weak interactions.
The underlying mechanism is driven by an emerging tunneling-energy gap in shallow few-well potentials. As a consequence, the interaction-energy gap that is expected to occur only for strong interactions in deep lattices is re-established.
By tuning the optical lattice depth, a crossover between two regimes with negligible particle number fluctuations is found: firstly, the common regime with vanishing spin-fluctuations in deep lattices and, secondly, a novel regime with strong spin fluctuations in shallow lattices.
We discuss the possible experimental realization with ultracold 40 K atoms and observable quantities in double wells and two-dimensional plaquettes. The dynamical control of tunneling processes of single particles plays a major role in science ranging from Shapiro steps in Josephson junctions to the control of chemical reactions via light in molecules.
Here we show how such control can be extended to the regime of correlated tunneling of strongly interacting particles. Through a periodic modulation of a biased tunnel contact, we have been able to coherently control single-particle and correlated two-particle hopping processes. We have furthermore been able to extend this control to superexchange spin interactions in the presence of a magnetic-field gradient. Such photon-assisted superexchange processes constitute a novel approach to realize arbitrary XXZ spin models in ultracold quantum gases, where transverse and Ising-type spin couplings can be fully controlled in magnitude and sign.
Superexchange -mediated magnetization dynamics with ultracold alkaline-earth atoms in an optical lattice. Superexchange and inter-orbital spin-exchange interactions are key ingredients for understanding orbital quantum magnetism in strongly correlated systems and have been realized in ultracold atomic gases. Here we study the spin dynamics of ultracold alkaline-earth atoms in an optical lattice when the two exchange interactions coexist. In the superexchange interaction dominating regime, we find that the time-resolved spin imbalance shows a remarkable modulated oscillation, which can be attributed to the interplay between local and nonlocal quantum mechanical exchange mechanisms.
Moreover, the filling of the long-lived excited atoms affects the collapse and revival of the magnetization dynamics. These observations can be realized in state-dependent optical lattices combined with the state-of-the-art advances in optical lattice clock spectroscopy. Silicon quantum dots QDs with diameters in the range of nm are attractive for photovoltaic applications. They absorb photons more readily, transport excitons with greater efficiency, and show greater promise in multiple-exciton generation and hot carrier collection paradigms.
However, their high excitonic binding energy makes it difficult to dissociate excitons into separate charge carriers. One possible remedy is to create dot assemblies in which a second material creates a Type-II heterojunction with the dot so that exciton dissociation occurs locally. This talk will focus on such a Type-II heterojunction paradigm in which QDs are connected via covalently bonded, short-bridge molecules.
For such interpenetrating networks of dots and molecules, our first principles computational investigation shows that it is possible to rapidly and efficiently separate electrons to QDs and holes to bridge units.
The bridge network serves as an efficient mediator of electron superexchange between QDs while the dots themselves play the complimentary role of efficient hole superexchange mediators. Dissociation, photoluminescence and carrier transport rates will be presented for bridge networks of silicon QDs that exhibit such double superexchange.
The T1 Cu and the remote catalytic sites are connected via a Cys-His intramolecular electron-transfer ET bridge, which contains two potential ET pathways: P1 through the protein backbone and P2 through the H-bond between the Cys and the His. The high covalency of the T1 Cu—S Cys bond is shown here to activate the T1 Cu site for hole superexchange via occupied valence orbitals of the bridge.
These pathways can be selectively activated depending on the geometric and electronic structure of the T1 Cu site and thus the anisotropic covalency of the T1 Cu—S Cys bond. These studies show that a given protein bridge, here Cys-His, provides different superexchange pathways and electronic couplings depending on the anisotropic covalencies of the donor and acceptor metal sites. Spin-orbital superexchange physics emerging from interacting oxygen molecules in KO2.
We propose that the spin-orbital-lattice coupled phenomena, widely known for the transition-metal oxides, can be realized in molecular solids, comprising of orbitally degenerate magnetic O 2 - ions. KO 2 is one such system. Using the first-principles electronic structure calculations, we set-up an effective spin-orbital superexchange model for the low-energy molecular bands and argue that many anomalous properties of KO 2 indeed replicate the status of its orbital system in different temperature regimes.
Moessbauer studies of superexchange interactions in NiFe sub 2 O sub 4. NiFe sub 2 O sub 4 has been studied using Moessbauer spectroscopy and X-ray diffraction. Moessbauer spectra of NiFe sub 2 O sub 4 was obtained at various absorber temperatures from 13 K to the Neel temperature.
The temperature dependence of the magnetic hyperfine fields at sup 5 sup 7 Fe nuclei at the tetrahedral A and the octahedral B sites was analyzed by the Neel theory of ferrimagnetism. Perturbation theory with respect to intercenter electron exchange and superexchange with degeneracy. The corrections to the energy and wave functions of a multielectron system of interacting atoms are calculated in a general analytic form by taking into account degeneracy of the states in accordance with the Young schemes.
The rule for writing down the perturbation operator in such systems is formulated in the case when the ground and excited state vectors are antisymmetrized with respect to interchange of electrons between the centers.
A secular equation of the theory is derived by applying perturbation theory, one of the parameters of which is the degree of overlap of the wave functions. Some concrete examples of interatomic interactions of an unpaired nature which are due to exchange and superexchange effects are considered.
Magnetic- superexchange interactions of uranium IV chloride-addition complexes with amides, 2. The magnetic susceptibilities of five cyclic amide lactam -addition complexes of uranium IV chloride were measured between room temperature and 2 K.
Magnetic-exchange interaction was found only for N-methyl-substituted amide complexes, and a dimer structure was assumed for them on the basis of their chemical properties.
Treating interdimer interaction with a molecular-field approximation, the magnetic susceptibilities were calculated to be in good agreement with the experimental results in the temperature region of the maxima in chi sub A. Assessing the performance of the random phase approximation for exchange and superexchange coupling constants in magnetic crystalline solids. The random phase approximation RPA for total energies has previously been shown to provide a qualitatively correct description of static correlation in molecular systems, where density functional theory DFT with local functionals are bound to fail.
This immediately poses the question of whether Due to strong electron localization, magnetic interactions in such systems are dominated by superexchange , which in the simplest picture can be regarded as the analog of static correlation Human Resourcing For CI.
The objective of this paper is therefore to define Data collection involved interviews and observations in three longitudinal studies in five companies based in Denmark.
Gierusz, Barbara (1952- ).
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Download as PDF or read. Original filename: B. The number of studies on the convergence of accounting is very limited in the world, and in Poland they are quite unique. The level of stratification is same for diesel and naphtha at various SOI. Three aspects are highlighted on CS production: The mixture homogeneity is enhanced for higher dilution due to longer ignition delay.