51 research outputs found
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
ΠΠ΅Π²ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΈ Π½Π΅ΠΉΡΠΎΡ ΠΈΡΡΡΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ Π°ΡΠΏΠ΅ΠΊΡΡ Π³ΠΈΠΏΠΎΡΠΎΡΡΠ°ΡΠ°Π·ΠΈΠΈ
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 βtonguesβ 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.ΠΠΈΠΏΠΎΡΠΎΡΡΠ°ΡΠ°Π·ΠΈΡ β ΡΠ΅Π΄ΠΊΠΎΠ΅ Π½Π°ΡΠ»Π΅Π΄ΡΡΠ²Π΅Π½Π½ΠΎΠ΅ ΠΏΡΠΎΠ³ΡΠ΅ΡΡΠΈΡΡΡΡΠ΅Π΅ Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π½ΠΈΠ΅, Π²ΡΠ·Π²Π°Π½Π½ΠΎΠ΅ ΠΌΡΡΠ°ΡΠΈΠ΅ΠΉ Π² Π³Π΅Π½Π΅ ALPL, Π²ΡΠ»Π΅Π΄ΡΡΠ²ΠΈΠ΅ ΠΊΠΎΡΠΎΡΠΎΠΉ ΡΠ³Π½Π΅ΡΠ°Π΅ΡΡΡ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ ΡΠ΅Π»ΠΎΡΠ½ΠΎΠΉ ΡΠΎΡΡΠ°ΡΠ°Π·Ρ. ΠΠ·-Π·Π° Π½Π°ΡΡΡΠ΅Π½ΠΈΡ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΠΌΠΈΠ½Π΅ΡΠ°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΊΠΎΡΡΠ½ΠΎΠΉ ΡΠΊΠ°Π½ΠΈ Π² ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΠ°ΡΡΠΈΠ½Π΅ ΠΏΡΠ΅ΠΎΠ±Π»Π°Π΄Π°ΡΡ ΡΠ°Ρ
ΠΈΡΠΎΠΏΠΎΠ΄ΠΎΠ±Π½ΡΠ΅ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ ΡΠΊΠ΅Π»Π΅ΡΠ°, Π½ΠΎ Π·Π°ΡΠ°ΡΡΡΡ Π²ΠΎΠ·Π½ΠΈΠΊΠ°ΡΡ ΠΈ Π΄ΡΡΠ³ΠΈΠ΅ ΡΠΈΡΡΠ΅ΠΌΠ½ΡΠ΅ ΠΏΡΠΎΡΠ²Π»Π΅Π½ΠΈΡ β Π½Π°ΡΡΡΠ΅Π½ΠΈΠ΅ Π΄ΡΡ
Π°Π½ΠΈΡ, ΠΏΠΎΡΠ°ΠΆΠ΅Π½ΠΈΠ΅ ΠΌΠΎΡΠ΅Π²ΡΠ΄Π΅Π»ΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ ΠΈ Π½Π΅Π²ΡΠΎΠ»ΠΎΠ³ΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΡΠ°ΡΡΡΡΠΎΠΉΡΡΠ²Π°. Π£ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠΎΠ² Π²ΡΡΠ²Π»ΡΡΡ ΡΡΠ΄ΠΎΡΠΎΠ³ΠΈ, Π·Π°Π΄Π΅ΡΠΆΠΊΡ ΡΠΈΠ·ΠΈΡΠ΅ΡΠΊΠΎΠ³ΠΎ ΠΈ ΠΏΡΠΈΡ
ΠΎΠΌΠΎΡΠΎΡΠ½ΠΎΠ³ΠΎ ΡΠ°Π·Π²ΠΈΡΠΈΡ, Π΄Π΅ΡΠΈΡΠΈΡ Π²Π½ΠΈΠΌΠ°Π½ΠΈΡ, ΠΌΡΡΠ΅ΡΠ½ΡΡ ΡΠ»Π°Π±ΠΎΡΡΡ, Π±ΡΡΡΡΡΡ ΡΡΠΎΠΌΠ»ΡΠ΅ΠΌΠΎΡΡΡ, Π²Π½ΡΡΡΠΈΡΠ΅ΡΠ΅ΠΏΠ½ΡΡ Π³ΠΈΠΏΠ΅ΡΡΠ΅Π½Π·ΠΈΡ, ΡΠ²ΡΠ·Π°Π½Π½ΡΡ Ρ ΡΠ°Π·Π²ΠΈΡΠΈΠ΅ΠΌ ΠΊΡΠ°Π½ΠΈΠΎΡΠΈΠ½ΠΎΡΡΠΎΠ·ΠΎΠ². Π’ΡΠΆΠ΅ΡΡΡ Π³ΠΈΠΏΠΎΡΠΎΡΡΠ°ΡΠ°Π·ΠΈΠΈ Π·Π°Π²ΠΈΡΠΈΡ ΠΎΡ Π²ΡΠ΅ΠΌΠ΅Π½ΠΈ Π΅Π΅ ΠΌΠ°Π½ΠΈΡΠ΅ΡΡΠ°ΡΠΈΠΈ: Π½Π°ΠΈΠ±ΠΎΠ»ΡΡΠ°Ρ ΡΠΌΠ΅ΡΡΠ½ΠΎΡΡΡ ΡΠ΅Π³ΠΈΡΡΡΠΈΡΡΠ΅ΡΡΡ ΠΏΡΠΈ ΠΏΠ΅ΡΠΈΠ½Π°ΡΠ°Π»ΡΠ½ΠΎΠΉ ΠΈ ΠΈΠ½ΡΠ°Π½ΡΠΈΠ»ΡΠ½ΠΎΠΉ ΡΠΎΡΠΌΠ°Ρ
Π·Π°Π±ΠΎΠ»Π΅Π²Π°Π½ΠΈΡ. ΠΠΈΠ°Π³Π½ΠΎΡΡΠΈΠΊΠ° ΠΎΡΠ½ΠΎΠ²Π°Π½Π° Π½Π° Π²ΡΡΠ²Π»Π΅Π½ΠΈΠΈ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠ½ΡΡ
ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠΈΠΌΠΏΡΠΎΠΌΠΎΠ² β Π·Π°Π΄Π΅ΡΠΆΠΊΠΈ ΡΠΎΡΡΠ° ΠΈ ΡΠ°Π·Π²ΠΈΡΠΈΡ, Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ ΡΠΊΠ΅Π»Π΅ΡΠ°, Π±ΠΎΠ»Π΅ΠΉ Π² ΠΌΡΡΡΠ°Ρ
ΠΈ ΡΡΡΡΠ°Π²Π°Ρ
, ΠΏΡΠ΅ΠΆΠ΄Π΅Π²ΡΠ΅ΠΌΠ΅Π½Π½ΠΎΠ³ΠΎ Π²ΡΠΏΠ°Π΄Π΅Π½ΠΈΡ Π·ΡΠ±ΠΎΠ². Π Π»Π°Π±ΠΎΡΠ°ΡΠΎΡΠ½ΡΡ
Π°Π½Π°Π»ΠΈΠ·Π°Ρ
ΠΎΡΡΠ»Π΅ΠΆΠΈΠ²Π°Π΅ΡΡΡ ΡΡΠΎΠΉΠΊΠΎΠ΅ ΡΠ½ΠΈΠΆΠ΅Π½ΠΈΠ΅ ΡΡΠΎΠ²Π½Ρ ΡΠ΅Π»ΠΎΡΠ½ΠΎΠΉ ΡΠΎΡΡΠ°ΡΠ°Π·Ρ Ρ ΡΡΠ΅ΡΠΎΠΌ Π²ΠΎΠ·ΡΠ°ΡΡΠ° ΠΈ ΠΏΠΎΠ»Π° ΠΏΠ°ΡΠΈΠ΅Π½ΡΠ°; ΠΏΡΠΈ Π½ΠΈΠ·ΠΊΠΎΠΉ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ ΡΠ΅ΡΠΌΠ΅Π½ΡΠ° ΡΡΠΎΠ²Π½ΠΈ ΡΡΠ±ΡΡΡΠ°ΡΠΎΠ² ΡΠ΅Π»ΠΎΡΠ½ΠΎΠΉ ΡΠΎΡΡΠ°ΡΠ°Π·Ρ ΠΏΠΈΡΠΈΠ΄ΠΎΠΊΡΠ°Π»Ρ-5-ΡΠΎΡΡΠ°Ρ Π² ΠΊΡΠΎΠ²ΠΈ ΠΈ ΡΠΎΡΡΠΎΡΡΠ°Π½ΠΎΠ»Π°ΠΌΠΈΠ½Π° Π² ΠΌΠΎΡΠ΅ Π²ΡΠ΅Π³Π΄Π° ΠΏΠΎΠ²ΡΡΠ΅Π½Ρ. ΠΠ° ΡΠ΅Π½ΡΠ³Π΅Π½ΠΎΠ³ΡΠ°ΠΌΠΌΠ°Ρ
Π΄Π»ΠΈΠ½Π½ΡΡ
ΡΡΡΠ±ΡΠ°ΡΡΡ
ΠΊΠΎΡΡΠ΅ΠΉ ΠΎΠ±Π½Π°ΡΡΠΆΠΈΠ²Π°ΡΡΡΡ Β«ΡΠ·ΡΠΊΠΈΒ» ΠΏΡΠΎΡΠ²Π΅ΡΠ»Π΅Π½ΠΈΡ, ΠΏΡΠΎΠ΅ΡΠΈΡΡΡΡΠΈΠ΅ΡΡ ΠΎΡ Π·ΠΎΠ½Ρ ΡΠΎΡΡΠ° Π² ΠΌΠ΅ΡΠ°ΡΠΈΠ·Ρ, Π° ΡΠ°ΠΊΠΆΠ΅ Π³ΠΈΠΏΠΎΠΌΠΈΠ½Π΅ΡΠ°Π»ΠΈΠ·Π°ΡΠΈΡ, ΠΎΡΡΠ΅ΠΎΠΏΠ΅Π½ΠΈΡ ΠΈ Π΄ΡΡΠ³ΠΈΠ΅ Π΄Π΅ΡΠΎΡΠΌΠ°ΡΠΈΠΈ. ΠΡΠ΅ ΠΏΠ°ΡΠΈΠ΅Π½ΡΡ Ρ ΠΏΠΎΠ΄ΠΎΠ·ΡΠ΅Π½ΠΈΠ΅ΠΌ Π½Π° Π³ΠΈΠΏΠΎΡΠΎΡΡΠ°ΡΠ°Π·ΠΈΡ Π΄ΠΎΠ»ΠΆΠ½Ρ Π±ΡΡΡ ΠΏΡΠΎΠΊΠΎΠ½ΡΡΠ»ΡΡΠΈΡΠΎΠ²Π°Π½Ρ ΠΊΠ»ΠΈΠ½ΠΈΡΠ΅ΡΠΊΠΈΠΌ Π³Π΅Π½Π΅ΡΠΈΠΊΠΎΠΌ ΠΈ ΠΎΠ±ΡΠ»Π΅Π΄ΠΎΠ²Π°Π½Ρ Π½Π° Π²ΡΡΠ²Π»Π΅Π½ΠΈΠ΅ ΠΌΡΡΠ°ΡΠΈΠΈ Π² Π³Π΅Π½Π΅ ALPL.ΠΠΠΠ€ΠΠΠΠ’ ΠΠΠ’ΠΠ ΠΠ‘ΠΠΠΠ²ΡΠΎΡΡ Π΄Π΅ΠΊΠ»Π°ΡΠΈΡΡΡΡ ΠΎΡΡΡΡΡΡΠ²ΠΈΠ΅ ΠΊΠΎΠ½ΡΠ»ΠΈΠΊΡΠΎΠ² ΠΈΠ½ΡΠ΅ΡΠ΅ΡΠΎΠ², ΡΠ²ΡΠ·Π°Π½Π½ΡΡ
Ρ ΠΏΡΠ±Π»ΠΈΠΊΠ°ΡΠΈΠ΅ΠΉ Π½Π°ΡΡΠΎΡΡΠ΅ΠΉ ΡΡΠ°ΡΡΠΈ
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