156 research outputs found
One-way quantum computation via manipulation of polarization and momentum qubits in two-photon cluster states
Four-qubit cluster states of two photons entangled in polarization and linear
momentum have been used to realize a complete set of single qubit rotations and
the C-NOT gate for equatorial qubits with high values of fidelity. By the
computational equivalence of the two degrees of freedom our result demonstrate
the suitability of two photon cluster states for rapid and efficient one-way
quantum computing.Comment: RevTex4, 4 pages, 3 figure
meV resolution in laser-assisted energy-filtered transmission electron microscopy
The electronic, optical, and magnetic properties of quantum solids are
determined by their low-energy (< 100 meV) many-body excitations. Dynamical
characterization and manipulation of such excitations relies on tools that
combine nm-spatial, fs-temporal, and meV-spectral resolution. Currently,
phonons and collective plasmon resonances can be imaged in nanostructures with
sub-nm and 10s meV space/energy resolution using state-of-the-art
energy-filtered transmission electron microscopy (TEM), but only under static
conditions, while fs-resolved measurements are common but lack spatial or
energy resolution. Here, we demonstrate a new method of spectrally resolved
photon-induced near-field electron microscopy (SRPINEM) that allows us to
obtain nm-fs-resolved maps of nanoparticle plasmons with an energy resolution
determined by the laser linewidth (20 meV in this work), and not limited by
electron beam and spectrometer energy spreading. This technique can be extended
to any optically-accessible low-energy mode, thus pushing TEM to a previously
inaccessible spectral domain with an unprecedented combination of space, energy
and temporal resolution.Comment: 19 pages, 7 figure
MCD and MCPL characterization of luminescent Si(IV) and P(V) tritolylcorroles: the role of coordination number
Two triarylcorrole complexes, (hydroxy)[5,10,15-tritolylcorrolato]silicon-(TTC)Si(OH) and (dihydroxy)[5,10,15-tritolylcorrolato]phosphorous-(TTC)P(OH)2, have been investigated by magnetic circular dichroism (MCD) and magnetic circularly polarized luminescence (MCPL). The spectroscopic investigations have been combined with explicit calculation of MCD response through time-dependent density functional theory (TD-DFT) formalism. This has allowed us to better define the role of molecular orbitals in the transitions associated with the Soret and Q bands. Besides and more importantly, MCD has made it possible to follow the titration process of (TTC)Si(OH) in dimethyl sulfoxide (DMSO) solution with NaF and of (TTC)P(OH)2 in dichloromethane solution with alcohols in a complementary and, we dare say, more sensitive way with respect to absorption and fluorescence data. Finally, the MCPL spectra and the ancillary TD-DFT calculations have allowed us to characterize the excited state of (TTC)Si(OH). © 2021 The Authors. Published by American Chemical Society
Enhancement of photoacoustic detection of inhomogeneities in polymers
We report a series of experiments on laser pulsed photoacoustic excitationin
turbid polymer samples addressed to evaluate the sound speed in the samples and
the presence of inhomogeneities in the bulk. We describe a system which allows
the direct measurement of the speed of the detected waves by engraving the
surface of the piece under study with a fiduciary pattern of black lines. We
also describe how this pattern helps to enhance the sensitivity for the
detection of an inhomogeneity in the bulk. These two facts are useful for
studies in soft matter systems including, perhaps, biological samples. We have
performed an experimental analysis on Grilon(R) samples in different situations
and we show the limitations of the method.Comment: 8 pages, 7 figure
Vertical MEMS Resonators for Real-Time Clock Applications
MEMS resonators are today widely investigated as a desirable alternative to quartz resonators in real-time clock applications, because of their low-cost, integration capability properties. Nevertheless, MEMS resonators performances are still not competitive, especially in terms of frequency stability and device equivalent resistance (and, then, power consumption). We propose a new structure for a MEMS resonator, with a vertical-like transduction mechanism, which exhibits promising features. The vertical resonator can be fabricated with the low-cost, high performance THELMA technology, and it is designed to be efficiently frequency tunable. With respect to the commonly investigated lateral resonators, it is expected to have lower equivalent resistances and improved large-scale repeatability characteristics
From attosecond to zeptosecond coherent control of free-electron wave functions using semi-infinite light fields
Light-electron interaction in empty space is the seminal ingredient for
free-electron lasers and also for controlling electron beams to dynamically
investigate materials and molecules. Pushing the coherent control of free
electrons by light to unexplored timescales, below the attosecond, would enable
unprecedented applications in light-assisted electron quantum circuits and
diagnostics at extremely small timescales, such as those governing
intramolecular electronic motion and nuclear phenomena. We experimentally
demonstrate attosecond coherent manipulation of the electron wave function in a
transmission electron microscope, and show that it can be pushed down to the
zeptosecond regime with existing technology. We make a relativistic pulsed
electron beam interact in free space with an appropriately synthesized
semi-infinite light field generated by two femtosecond laser pulses reflected
at the surface of a mirror and delayed by fractions of the optical cycle. The
amplitude and phase of the resulting coherent oscillations of the electron
states in energymomentum space are mapped via momentum-resolved ultrafast
electron energy-loss spectroscopy. The experimental results are in full
agreement with our theoretical framework for light-electron interaction, which
predicts access to the zeptosecond timescale by combining semi-infinite X-ray
fields with free electrons.Comment: 22 pages, 6 figure
Chiral recognition with broad selective sensor arrays
The detection and discrimination of chiral analytes has always been a topical theme in food and pharmaceutical industries and environmental monitoring, especially when dealing with chiral drugs and pesticides, whose enantiomeric nature assessment is of crucial importance. The typical approach matches novel chiral receptors designed ad hoc for the discrimination of a target enantiomer with emerging nanotechnologies. The massive synthetic efforts requested and the difficulty of analyzing complex matrices warrant the ever-growing exploitation of sensor array as an alternative route, using a limited number of chiral or both chiral and achiral sensors for the stereoselective identification and dosing of chiral compounds. This review aims to illustrate a little-explored winning strategy in chiral sensing based on sensor arrays. This strategy mimics the functioning of natural olfactory systems that perceive some couples of enantiomeric compounds as distinctive odors (i.e., using an array of a considerable number of broad selective receptors). Thus, fundamental concepts related to the working principle of sensor arrays and the role of data analysis techniques and models have been briefly presented. After the discussion of existing examples in the literature using arrays for discriminating enantiomers and, in some cases, determining the enantiomeric excess, the remaining challenges and future directions are outlined for researchers interested in chiral sensing applications
Room Temperature CO Detection by Hybrid Porphyrin-ZnO Nanoparticles
AbstractPorphyrins are the natural candidates to the detection of carbon monoxide however the physical properties of solid-state layers of porphyrins limit their use as gas sensors mainly with mass and optical transducers. Recently we shown that the photonic properties of porphyrins, brilliantly exploited in organic solar cells, can lead to a new class of photo-activated sensors made by porphyrins coated metal oxides. Here we investigate the sensitivity to carbon monoxide of resistive sensors made by zinc oxide nanoparticles coated by a porphyrin layer. Sensors were prepared following two different routes and tested, at room temperature and in various light conditions, to CO and few volatile compounds. Results show a significant sensitivity and selectivity to CO
Laser-Induced Skyrmion Writing and Erasing in an Ultrafast Cryo-Lorentz Transmission Electron Microscopy
We demonstrate that light-induced heat pulses of different duration and
energy can write skyrmions in a broad range of temperatures and magnetic field
in FeGe. Using a combination of camera-rate and pump-probe cryo-Lorentz
Transmission Electron Microscopy, we directly resolve the spatio-temporal
evolution of the magnetization ensuing optical excitation. The skyrmion lattice
was found to maintain its structural properties during the laser-induced
demagnetization, and its recovery to the initial state happened in the
sub-{\mu}s to {\mu}s range, depending on the cooling rate of the system
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