Quantum metamaterial without local control

A quantum metamaterial can be implemented as a quantum coherent 1D array of qubits placed in a transmission line. The properties of quantum metamaterials are determined by the local quantum state of the system. Here we show that a spatially-periodic quantum state of such a system can be realized without direct control of the constituent qubits, by their interaction with the initializing ("priming") pulses sent through the system in opposite directions. The properties of the resulting quantum photonic crystal are determined by the choice of the priming pulses. This proposal can be readily generalized to other implementations of quantum metamaterials.Comment: 6 pages, 5 figure

Raman fingerprints of ultrasmall nanodiamonds produced from adamantane

The synthesis of ultrasmall (2-5 nm) nanodiamonds purely from adamantane at pressure of 12 GPa is reported. Their structural features have been studied by Raman spectroscopy. The unusual vibration band containing a number of pronounced maxima at about 1147, 1245, 1344, and 1456 cm-1 was detected in Raman spectra. The band is confidently identified with the bending vibrational modes of CHx groups terminating the nanodiamonds surface. Excessively intense mode at 1344 cm-1 is explained by its coupling with the 1328 cm-1 diamond phonons. The Raman band found is proposed to be used for express recognition of ultrasmall nanodiamonds produced from adamantane and other hydrocarbons with a high hydrogen content. Moreover, polarized CH bonds on a diamond surface are sensitive to environmental conditions. This opens up opportunities for using the diamond produced from adamantane as ultrasmall nanosensors in biology, chemistry, and medicineComment: 12 pages, 6 figure

Donor-acceptor recombination emission in hydrogen-terminated nanodiamond: Novel single-photon source for room-temperature quantum photonics

In fluorescence spectra of nanodiamonds (NDs) synthesized at high pressure from adamantane and other organic compounds, very narrow (~1 nm) lines of unknown origin are observed in a wide spectroscopic range from ~500 to 800 nm. Here, we propose and experimentally substantiate the hypothesis that these mysterious lines arise from radiative recombination of donor-acceptor pairs (DAPs). To confirm our hypothesis, we study the fluorescence spectra of undoped and nitrogen-doped NDs of different sizes, before and after thermal oxidation of their surface. The results obtained with a high degree of confidence allowed us to conclude that the DAPs are formed through the interaction of donor-like substitutional nitrogen present in the diamond lattice, and a 2D layer of acceptors resulting from the transfer doping effect on the surface of hydrogen-terminated NDs. A specific behavior of the DAP-induced lines was discovered in the temperature range of 100-10 K: their energy increases and most lines are split into 2 or more components with decreasing temperature. It is shown that the majority of the studied DAP emitters are sources of single photons, with an emission rate of up to >1 million counts/s at room temperature, which significantly surpasses that of nitrogen-vacancy and silicon-vacancy centers under the same detection conditions. Despite an observed temporal instability in the emission, the DAP emitters of H-terminated NDs represent a powerful room-temperature single-photon source for quantum optical technologies

Amplitude spectroscopy of two coupled qubits

We study the effect of a time-dependent driving field with a large amplitude on a system composed of two coupled qubits (two-level systems). Using the rotating wave approximation (RWA) makes it possible to find simple conditions for resonant excitation of the four-level system. We find that the resonance conditions include the coupling strength between the qubits. Numerical simulations confirm the qualitative conclusions following from the RWA. To reveal the peculiarities of resonant transitions caused by the quasi-level motion and crossing in a periodic driving field, we use Floquet states, which determine the precise intermediate states of the system. Calculating the quasi-energy states of the multi-level system makes it possible to find the transition probabilities and build interference patterns for the transition probabilities. The interference patterns demonstrate the possibility of obtaining various pieces of information about the qubits, since the positions of transition-probability maxima depend on various system parameters, including the coupling strength between the qubits.Comment: 9 pages, 6 figure

A Molecular Platinum Cluster Junction: A Single-Molecule Switch

We present a theoretical study of the electronic transport through single-molecule junctions incorporating a Pt6 metal cluster bound within an organic framework. We show that the insertion of this molecule between a pair of electrodes leads to a fully atomically engineered nano-metallic device with high conductance at the Fermi level and two sequential high on/off switching states. The origin of this property can be traced back to the existence of a HOMO which consists of two degenerate and asymmetric orbitals, lying close in energy to the Fermi level of the metallic leads. Their degeneracy is broken when the molecule is contacted to the leads, giving rise to two resonances which become pinned close to the Fermi level and display destructive interference.Comment: 4 pages, 4 figures. Reprinted (adapted) with permission from J. Am. Chem. Soc., 2013, 135 (6), 2052. Copyright 2013 American Chemical Societ

Неврологические и нейрохирургические аспекты гипофосфатазии

Hypophosphatasia is a rare hereditary progressive disease caused by a mutation in ALPL gene and characterized by low activity of alkaline phosphatase. Due to the disruption of the bone mineralization process, ricket-like deformations of the skeleton occur in the clinic picture more frequently but other systemic manifestations can be also observed as respiratory insufficiency, urinary tract damage, and neurological disorders. Seizures, delayed physical and psychomotor development, attention deficit disorder, muscle weakness, fatigue, intracranial hypertension associated with the development of craniosynostosis are revealed in these patients. The severity of the disease depends on age: the highest mortality is reported in younger patients, in perinatal and infantile forms of hypophosphatasia. Diagnosis is based on the identification of specific clinical manifestations: retardation of growth and development, skeletal deformities, pain in muscles and joints, premature tooth loss. In laboratory tests, a steady decrease in alkaline phosphatase level is detected taking into account age and sex specification. If possible, alkaline phosphatase substrates are measured: levels of pyridoxal-5-phosphate in the blood and phosphoethanolamine in urine are higher at low enzyme activity. Radiographs of long bones typically reveal characteristic ‘tongues’ of lucency projecting from growth plates into metaphyses, hypomineralization, osteopenia, various kinds of deformation. All patients with suspected hypophosphatasia should be consulted by a clinical geneticist and evaluated to identify possible mutation in the ALPL gene.Гипофосфатазия — редкое наследственное прогрессирующее заболевание, вызванное мутацией в гене ALPL, вследствие которой угнетается активность щелочной фосфатазы. Из-за нарушения процесса минерализации костной ткани в клинической картине преобладают рахитоподобные деформации скелета, но зачастую возникают и другие системные проявления — нарушение дыхания, поражение мочевыделительной системы и неврологические расстройства. У пациентов выявляют судороги, задержку физического и психомоторного развития, дефицит внимания, мышечную слабость, быструю утомляемость, внутричерепную гипертензию, связанную с развитием краниосиностозов. Тяжесть гипофосфатазии зависит от времени ее манифестации: наибольшая смертность регистрируется при перинатальной и инфантильной формах заболевания. Диагностика основана на выявлении характерных клинических симптомов — задержки роста и развития, деформации скелета, болей в мышцах и суставах, преждевременного выпадения зубов. В лабораторных анализах отслеживается стойкое снижение уровня щелочной фосфатазы с учетом возраста и пола пациента; при низкой активности фермента уровни субстратов щелочной фосфатазы пиридоксаль-5-фосфат в крови и фосфоэтаноламина в моче всегда повышены. На рентгенограммах длинных трубчатых костей обнаруживаются «языки» просветления, проецирующиеся от зоны роста в метафизы, а также гипоминерализация, остеопения и другие деформации. Все пациенты с подозрением на гипофосфатазию должны быть проконсультированы клиническим генетиком и обследованы на выявление мутации в гене ALPL.КОНФЛИКТ ИНТЕРЕСОВАвторы декларируют отсутствие конфликтов интересов, связанных с публикацией настоящей статьи