Functional renormalization group study of parallel double quantum dots: Effects of asymmetric dot-lead couplings

We explore the effects of asymmetry of hopping parameters between double parallel quantum dots and the leads on the conductance and a possibility of local magnetic moment formation in this system using functional renormalization group approach with the counterterm. We demonstrate a possibility of a quantum phase transition to a local moment regime (so called singular Fermi liquid (SFL) state) for various types of hopping asymmetries and discuss respective gate voltage dependences of the conductance. It is shown, that depending on the type of the asymmetry, the system can demonstrate either a first order quantum phase transition to SFL state, accompanied by a discontinuous change of the conductance, similarly to the symmetric case, or the second order quantum phase transition, in which the conductance is continuous and exhibits Fano-type asymmetric resonance near the transition point. A semi-analytical explanation of these different types of conductance behavior is presented.Comment: 11 pages, 9 figure

Local magnetic moments and electronic transport in closed loop quantum dot systems: a case of quadruple quantum dot ring at and away from equilibrium

We apply the non-equilibrium functional renormalization group approach treating flow of the electronic self-energies, to describe local magnetic moments formation and electronic transport in a quadruple quantum dot (QQD) ring, coupled to leads, with moderate Coulomb interaction on the quantum dots. We find that at zero temperature depending on parameters of the QQD system the regimes with zero, one, or two almost local magnetic moments in the ring can be realized, and the results of the considered approach in equilibrium agree qualitatively with those of more sophisticated fRG approach treating also flow of the vertices. It is shown that the almost formed local magnetic moments, which exist in the equilibrium, remain stable in a wide range of bias voltages near equilibrium. The destruction of the local magnetic moments with increasing bias voltage is realized in one or two stages, depending on the parameters of the system; for two-stage process the intermediate phase possesses fractional magnetic moment. We present zero-temperature results for current-voltage dependences and differential conductances of the system, which exhibit sharp features at the transition points between different magnetic states. The occurrence of interaction induced negative differential conductance phenomenon is demonstrated and discussed. For one local moment in the ring and finite hopping between the opposite quantum dots, connected to the leads, we find suppression of the conductance for one of the spin projections in infinitesimally small magnetic field, which occurs due to destructive interference of different electron propagation paths and can be used in spintronic devices.Comment: 19 pages, 19 figure

ІНФОРМАЦІЙНЕ ВІДДЗЕРКАЛЕННЯ ПРОБЛЕМ ФІНАНСОВОГО ЗАБЕЗПЕЧЕННЯ ПЛАНУВАННЯ КАДРОВИХ РЕСУРСІВ

Two ways to indentify sources of funding for workforce planning of health care provided limited funds. Emphasized that investment in education is a source of economic growth. Clear boundaries between investment in public education (receiving general education) and private investment (vocational training) does not exist. A possi ble solution to the problem of harmonization of investment policies can be informatization training system that misses factors industry research, motivation, training difficulties, financial calculations.Рассмотрены два пути определения источников финансирования для планирования кадровых ресурсов системы здравоохранения при условии ограниченности денежных средств. Подчеркнуто, что инвестиции в образование является источником экономического роста. Четких границ между инвестициями общества в образование (получение общеобразовательной подготовки) и частными инвестициями (получение профессиональной подготовки) не существует. Возможным решением проблемы гармонизации инвестиционной политики может стать информатизация системы подготовки кадров, что суммирует факторы потребностей отрасли, мотивации труда, трудности подготовки, финансов ые расчеты.Розглянуто два шляхи визначення джерел фінансування для планування кадрових ресурсів системи охорони здоров'я за умови обмеженості грошових коштів. Підкреслено, що інвестиції в освіту є джерелом економічного зростання. Чітких меж між інвестиціями суспільства в освіту (отримання загальноосвітньої підготовки) та приватними інвестиціями (отримання професійної підготовки) не існує. Можливим рішенням проблеми гармонізації інвестиційної політики може стати інформатизація системи підготовки кадрів, що сумує фактори потреб галузі, мотивації праці, труднощі підготовки, фінансові розрахунки

Формирование и внедрение новых компонентов развития, которые повышают конкурентоспособность предприятия

У статті розглядаються основні напрями та нові компоненти підвищення конкурентоспроможності підприємств, які залежать від їх потенційних можливостей, умов реалізації стратегічних напрямів, розвитку і використання ресурсного забезпечення.The paper examines the main trends and new components enhance the competitiveness of enterprises, depending on the capabilities, the conditions of strategic direction, development and utilization of resources. The criteria of competitiveness evaluation, methods and mechanisms for their implementation, their uses are described advantages and disadvantages of each. Detailed analysis of approaches to the selection of the parameters that characterize the individual components of multifactorial concept of «competitiveness». The recommendations on the implementation process of comparing totals that determine the competitiveness of enterprises. measured. The ways of implementing the strategy of innovative development, as the basic conditions for the formation of the intellectual potential of the company and society.В статье рассматриваются основные направления и новые компоненты повышения конкурентоспособности предприятий, которые зависят от их потенциальных возможностей, условий реализации стратегических направлений, развития и использования ресурсного обеспечения

Conditional quantum logic using two atomic qubits

In this paper we propose and analyze a feasible scheme where the detection of a single scattered photon from two trapped atoms or ions performs a conditional unitary operation on two qubits. As examples we consider the preparation of all four Bell states, the reverse operation that is a Bell measurement, and a CNOT gate. We study the effect of atomic motion and multiple scattering, by evaluating Bell inequalities violations, and by calculating the CNOT gate fidelity.Comment: 23 pages, 8 figures in 11 file

Interaction-induced local moments in parallel quantum dots within the functional renormalization group approach

We propose a version of the functional renormalization-group (fRG) approach, which is, due to including Litim-type cutoff and switching off (or reducing) the magnetic field during fRG flow, capable of describing a singular Fermi-liquid (SFL) phase, formed due to the presence of local moments in quantum dot structures. The proposed scheme allows one to describe the first-order quantum phase transition from the "singular" to the "regular" paramagnetic phase with applied gate voltage to parallel quantum dots, symmetrically coupled to leads, and shows sizable spin splitting of electronic states in the SFL phase in the limit of vanishing magnetic field H→0; the calculated conductance shows good agreement with the results of the numerical renormalization group. Using the proposed fRG approach with the counterterm, we also show that for asymmetric coupling of the leads to the dots the SFL behavior similar to that for the symmetric case persists, but with occupation numbers, effective energy levels, and conductance changing continuously through the quantum phase transition into the SFL phase. © 2016 American Physical Society