Shock Waves in Nanomechanical Resonators

The dream of every surfer is an extremely steep wave propagating at the highest speed possible. The best waves for this would be shock waves, but are very hard to surf. In the nanoscopic world the same is true: the surfers in this case are electrons riding through nanomechanical devices on acoustic waves [1]. Naturally, this has a broad range of applications in sensor technology and for communication electronics for which the combination of an electronic and a mechanical degree of freedom is essential. But this is also of interest for fundamental aspects of nano-electromechanical systems (NEMS), when it comes to quantum limited displacement detection [2] and the control of phonon number states [3]. Here, we study the formation of shock waves in a NEMS resonator with an embedded two-dimensional electron gas using surface acoustic waves. The mechanical displacement of the nano-resonator is read out via the induced acoustoelectric current. Applying acoustical standing waves we are able to determine the anomalous acoustocurrent. This current is only found in the regime of shock wave formation. We ontain very good agreement with model calculations.Comment: 14 Pages including 4 figure

Spectroscopic Interpretation: The High Vibrations of CDBrClF

We extract the dynamics implicit in an algebraic fitted model Hamiltonian for the deuterium chromophore's vibrational motion in the molecule CDBrClF. The original model has 4 degrees of freedom, three positions and one representing interbond couplings. A conserved polyad allows in a semiclassical approach the reduction to 3 degrees of freedom. For most quantum states we can identify the underlying motion that when quantized gives the said state. Most of the classifications, identifications and assignments are done by visual inspection of the already available wave function semiclassically transformed from the number representation to a representation on the reduced dimension toroidal configuration space corresponding to the classical action and angle variables. The concentration of the wave function density to lower dimensional subsets centered on idealized simple lower dimensional organizing structures and the behavior of the phase along such organizing centers already reveals the atomic motion. Extremely little computational work is needed.Comment: 23 pages, 6 figures. Accepted for publication in J. Chem. Phy

The Resonant Exchange Qubit

We introduce a solid-state qubit in which exchange interactions among confined electrons provide both the static longitudinal field and the oscillatory transverse field, allowing rapid and full qubit control via rf gate-voltage pulses. We demonstrate two-axis control at a detuning sweet-spot, where leakage due to hyperfine coupling is suppressed by the large exchange gap. A {\pi}/2-gate time of 2.5 ns and a coherence time of 19 {\mu}s, using multi-pulse echo, are also demonstrated. Model calculations that include effects of hyperfine noise are in excellent quantitative agreement with experiment

Coherent photonuclear reactions for isotope transmutation

Coherent photonuclear isotope transmutation (CPIT) produces exclusively radioactive isotopes (RIs) by coherent photonuclear reactions via E1 giant resonances. Photons to be used are medium energy photons produced by laser photons backscattered off GeV electrons. The cross sections are as large as 0.2 - 0.6 b, being independent of individual nuclides. A large fraction of photons is effectively used for the photonuclear reactions, while the scattered GeV electrons remain in the storage ring to be re-used. CPIT with medium energy photons provides specific/desired RIs with the high rate and the high density for nuclear science, molecular biology and for nuclear medicines.Comment: 8 pages, 2 figure

Self-Consistent Measurement and State Tomography of an Exchange-Only Spin Qubit

We report initialization, complete electrical control, and single-shot readout of an exchange-only spin qubit. Full control via the exchange interaction is fast, yielding a demonstrated 75 qubit rotations in under 2 ns. Measurement and state tomography are performed using a maximum-likelihood estimator method, allowing decoherence, leakage out of the qubit state space, and measurement fidelity to be quantified. The methods developed here are generally applicable to systems with state leakage, noisy measurements, and non-orthogonal control axes.Comment: contains Supplementary Informatio

Dynamic Rabi Oscillations in a Quantum Dot Embedded in a Nanobridge in the Presence of Surface Acoustic Waves

A quantum dot is created within a suspended nanobridge containing a two-dimensional electron gas. The electron current through this dot exhibits well-pronounced Coulomb blockade oscillations. When surface acoustic waves (SAW) are driven through the nanobridge, Coulomb blockade peaks are shifted. To explain this feature, we derive the expressions for the quantum dot level populations and electron currents through these levels and show that SAW-induced Rabi oscillations lead to the observed phenomenology

The good, the bad and the ugly: pandemic priority decisions and triage.

In this analysis we discuss the change in criteria for triage of patients during three different phases of a pandemic like COVID-19, seen from the critical care point of view. Availability of critical care beds has become a hot topic, and in many countries, we have seen a huge increase in the provision of temporary intensive care bed capacity. However, there is a limit where the hospitals may run out of resources to provide critical care, which is heavily dependent on trained staff, just-in-time supply chains for clinical consumables and drugs and advanced equipment. In the first (good) phase, we can still do clinical prioritisation and decision-making as usual, based on the need for intensive care and prognostication: what are the odds for a good result with regard to survival and quality of life. In the next (bad phase), the resources are mostly available, but the system is stressed by many patients arriving over a short time period and auxiliary beds in different places in the hospital being used. We may have to abandon admittance of patients with doubtful prognosis. In the last (ugly) phase, usual medical triage and priority setting may not be sufficient to decrease inflow and there may not be enough intensive care unit beds available. In this phase different criteria must be applied using a utilitarian approach for triage. We argue that this is an important transition where society, and not physicians, must provide guidance to support triage that is no longer based on medical priorities alone

Повышение энергоэффективности Республики Марий Эл путем внедрения АСКУЭ

Plasma-treated polymers typically show changes of surface morphology as well as modifications in their chemical composition. Both effects are known to have an influence on deposition and adhesion of metal coatings, although the exact mechanisms are not yet understood. Besides high- energy electrons and chemically active species, the generated UV radiation is one major component of plasma surface modification. The energy of ultraviolet photons is sufficiently high to induce bond scissions in polymeric materials, which result in subsequent chemical reactions. In this study, excimer radiation from lasers (e.g. KrF, 248nm) or lamps (e.g. KrCI, 222nm) was used for the formation of polar functional groups on the surface. The treatment was carried out at atmospheric pressure, mostly in air. The chemical and physical properties of the irradiated surface are different compared with untreated areas. The resulting functional groups allow for a spontaneous deposition of molecular thin films from aqueous solutions. In particular, these can be complexes from noble metals. Noble metals catalyze deposition in electroless metallization baths. A process for selective metal deposition on polymers has been developed based on this principle. After deposition, the main issue is the adhesion that can be achieved in the polymer-metal interface. It is determined by chemical or physical interaction between the polymer surface and the adjacent layer, as well as by typographical features