Dipole lasing phase transitions in media with singularities in polarizabilities

We show that a divergence in the optical polarizability of a heterogeneous medium with nonlinear amplification and a strong dipole-dipole interaction between particles can lead to a phase transition, for which the dipole momentum of the particles or the dipole radiation rate can be taken as order parameters. The "dipole laser" (Phys. Rev. A 71, 063812 (2005)) can be used both as a simple example of such a second-order phase transition and to provide a recipe for its analysis. We show that similar phase transitions may be possible for a nanoparticle on the surface of an optically active medium and at the "Clausius-Mossotti" catastrophe in a bulk heterogeneous medium

Dipole nanolaser

A "dipole" laser is proposed consisting of a nanoparticle and a two-level system with population inversion. If the threshold conditions are fulfilled, the dipole interaction between the two-level system and the nanoparticle leads to coherent oscillations in the polarization of the particles, even in the absence of an external electromagnetic field. The emitted radiation has a dipolar distribution. It does not need an optical cavity, and has a very small volume, 0.1 mu m(3), which can be important for applications in microelectronics. Estimates of the threshold conditions are carried out for a dipole laser composed of a quantum dot and a silver nanoparticle

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

Photon polarisation entanglement from distant dipole sources

It is commonly believed that photon polarisation entanglement can only be obtained via pair creation within the same source or via postselective measurements on photons that overlapped within their coherence time inside a linear optics setup. In contrast to this, we show here that polarisation entanglement can also be produced by distant single photon sources in free space and without the photons ever having to meet, if the detection of a photon does not reveal its origin -- the which way information. In the case of two sources, the entanglement arises under the condition of two emissions in certain spatial directions and leaves the dipoles in a maximally entangled state.Comment: 7 pages, 2 figures, revised version, accepted for publication in J. Phys.

Broadening of Plasmonic Resonance Due to Electron Collisions with Nanoparticle Boundary: а Quantum Mechanical Consideration

We present a quantum mechanical approach to calculate broadening of plasmonic resonances in metallic nanostructures due to collisions of electrons with the surface of the structure. The approach is applicable if the characteristic size of the structure is much larger than the de Broglie electron wavelength in the metal. The approach can be used in studies of plasmonic properties of both single nanoparticles and arrays of nanoparticles.Comment: 9 page

Comparison of Theory and Experiment for a One-Atom Laser in a Regime of Strong Coupling

Our recent paper reports the experimental realization of a one-atom laser in a regime of strong coupling (Ref. [1]). Here we provide the supporting theoretical analysis relevant to the operating regime of our experiment. By way of a simplified four-state model, we investigate the passage from the domain of conventional laser theory into the regime of strong coupling for a single intracavity atom pumped by coherent external fields. The four-state model is also employed to exhibit the vacuum-Rabi splitting and to calculate the optical spectrum. We next extend this model to incorporate the relevant Zeeman hyperfine states as well as a simple description of the pumping processes in the presence of polarization gradients and atomic motion. This extended model is employed to make quantitative comparisons with the measurements of Ref. [1] for the intracavity photon number versus pump strength and for the photon statistics as expressed by the intensity correlation function g2(tau).Comment: 19 pages, 14 figures. Added sections on: scaling properties, vacum-Rabi splitting, and optical spectru

Plasmonic atoms and plasmonic molecules

The proposed paradigm of plasmonic atoms and plasmonic molecules allows one to describe and predict the strongly localized plasmonic oscillations in the clusters of nanoparticles and some other nanostructures in uniform way. Strongly localized plasmonic molecules near the contacting surfaces might become the fundamental elements (by analogy with Lego bricks) for a construction of fully integrated opto-electronic nanodevices of any complexity and scale of integration.Comment: 30 pages, 16 figure

Quantum computing in optical microtraps based on the motional states of neutral atoms

We investigate quantum computation with neutral atoms in optical microtraps where the qubit is implemented in the motional states of the atoms, i.e., in the two lowest vibrational states of each trap. The quantum gate operation is performed by adiabatically approaching two traps and allowing tunneling and cold collisions to take place. We demonstrate the capability of this scheme to realize a square-root of swap gate, and address the problem of double occupation and excitation to other unwanted states. We expand the two-particle wavefunction in an orthonormal basis and analyze quantum correlations throughout the whole gate process. Fidelity of the gate operation is evaluated as a function of the degree of adiabaticity in moving the traps. Simulations are based on rubidium atoms in state-of-the-art optical microtraps with quantum gate realizations in the few tens of milliseconds duration range.Comment: 11 pages, 7 figures, for animations of the gate operation, see http://www.itp.uni-hannover.de/~eckert/na/index.htm

Анализ структуры бактериемий и чувствительности к антибиотикам микроорганизмов, выделенных в отделениях реанимации и интенсивной терапии в скоропомощном стационаре в период с 2003 по 2021 г.: ретроспективное наблюдательное исследование

АКТУАЛЬНОСТЬ: Создание протоколов эффективной эмпирической антимикробной терапии невозможно без анализа актуальных данных чувствительности к антибиотикам. ЦЕЛЬ ИССЛЕДОВАНИЯ: Анализ изменения этиологической значимости ведущих возбудителей бактериемий в отделении реанимации и интенсивной терапии (ОРИТ) в период с 2003 по 2021 г. и их чувствительности к антибиотикам; изучение типов карбапенемаз у наиболее актуальных возбудителей — Klebsiella pneumoniae и Acinetobacter baumannii. МАТЕРИАЛЫ И МЕТОДЫ: В анализ были включены все клинически значимые микроорганизмы, выделенные из крови пациентов, находившихся ОРИТ общего профиля, рассчитанном на 12 коек, в скоропомощном стационаре г. Москвы в период с 2003 по 2021 г. Идентификацию микроорганизмов и определение чувствительности к антибиотикам проводили в автоматическом анализаторе PHOENIX и стандартизированным диско-диффузионным методом. Детекцию карбапенемаз осуществляли методом полимеразной цепной реакции. РЕЗУЛЬТАТЫ: Исследовано 17 034 образца крови, из которых было выделено 6372 микроорганизма. В указанный период доля грамотрицательных микроорганизмов увеличилась с 21,0 до 52,8 %, преимущественно за счет K. pneumoniae (1,0–24,5 %) и A. baumannii (0–9,1 %). Устойчивость этих микроорганизмов к карбапенемам с 2008 по 2021 г. значительно увеличилась: K. pneumoniae — с 2,3 до 70,3 %, A. baumannii — с 7,5 до 99,5 %. Штаммы K. pneumoniae продуцировали следующие типы карбапенемаз: OXA-48 (73,8 %), KPC (6,2 %), NDM (1,5 %), NDM + OXA-48 (15,4 %), KPC + OXA-48 (3,1 %). Все штаммы A. baumannii продуцировали карбапенемазы OXA-40. Продуценты карбапенемазы OXA-48 были устойчивы к колистину и тигециклину в 14,6 и 44,8 % случаев соответственно, к цефтазидиму/авибактаму — в 4,2 % случаев. ВЫВОДЫ: Увеличение уровня антимикробной резистентности в последние годы среди доминирующих в бактериемии грамотрицательных микроорганизмов является очень значимой проблемой в ОРИТ. Большинство штаммов K. pneumoniae характеризуются множественной резистентностью и около 10 % — экстремальной, или панрезистентностью. Практически все штаммы A. baumannii относятся к категории экстремально резистентных

Studyng the effects of Cantharellus cibarius fungi on Opisthorchis felineus trematode and on parasite host - C57BL/6 inbred mice

Opisthorchiasis is a dangerous parasitic disease caused by trematodes in the family Opisthorchiidae. One of the causes of this infection is the species Opisthorchis felineus, which is common in the Russian Federation and Western Europe. The disease has a large number of complications and relatively few effective treatments, so nowadays it is relevant to look for new drugs for the treatment of opisthorchiasis, with the maximum antiparasitic and minimal side effect. In this work, a potentially anthelmintic effect of the methanol extract of the golden chanterelle mushroom (Cantharellus cibarius) was investigated. In in vitro experiments, the significantly reduced mobility and survival rates of juvenile O. felineus specimens with increasing concentrations (10-1000 pg/ml) of the C. cibarius extract were shown. In in vivo studies, administration of the C. cibarius extract on the first day after parasitic infection of inbred C57BL/6 mice resulted in a decrease of the number of helminths in the bile ducts of the liver, evaluated 6 weeks after infection. In another series of experiments, administration of the C. cibarius extract for 7 days to mice infected with O. felineus for five weeks had no anthelmintic effect. In both cases, the state of the infected hosts, evaluated by a number of physiological and biochemical parameters (relative weight of organs, blood indices), did not deteriorate, indicating that there was no adverse effect of the C. cibarius extract. The results obtained suggest that the C. cibarius extract might have anthelmintic properties if applied as parasite larvae excyst