40 research outputs found
Nanomechanical resonators operating as charge detectors in the nonlinear regime
We present measurements on nanomechanical resonators machined from
Silicon-on-Insulator substrates. The resonators are designed as freely
suspended Au/Si beams of lengths on the order of 1 - 4 um and a thickness of
200 nm. The beams are driven into nonlinear response by an applied modulation
at radio frequencies and a magnetic field in plane. The strong hysteresis of
the magnetomotive response allows sensitive charge detection by varying the
electrostatic potential of a gate electrode.Comment: 8 pages, 6 figure
Radiographer gender and breast-screening uptake
BreastCheck, the Irish National Breast Screening Programme, screens women aged 50–64. Radiographer recruitment has been a challenge; doubling of numbers is required for full national expansion; to date females are employed. The aim was to document attitudes to male radiographers and effect on return for subsequent screening. In all 85.8% of a random sample of 2000 women recently screened by BreastCheck completed a postal questionnaire. The commonest reaction women felt they would have if there were a male radiographer was embarrassment; significantly greater among those attending a static unit (45.6%) than mobile (38.4%) and in younger women (46%) than older (38.7%). Nine per cent would not have proceeded if the radiographer was male and 9% would only have proceeded if female chaperone present. In all 17.5% (95% CI 15.7–19.4%) agreed that ‘If there were male radiographers I would not return for another screening appointment'; 18.3% were unsure. One-quarter agreed ‘if I heard there could be male radiographers it would change my opinion of BreastCheck for the worse'. The proportions agreeing with these statements did not vary significantly by screening unit type, age group, area of residence or insurance status. This is the largest published study to date of this important issue; the correct balance between equality and programme performance must be identified
Coherent coupling of two quantum dots embedded in an Aharonov-Bohm ring
We define two laterally gated small quantum dots (~ 15 electrons) in an
Aharonov-Bohm geometry in which the coupling between the two dots can be
broadly changed. For weakly coupled quantum dots we find Aharonov-Bohm
oscillations. In an intermediate coupling regime we concentrate on the
molecular states of the double dot and extract the magnetic field dependence of
the coherent coupling.Comment: 6 pages, 4 figure
Coherent Single Charge Transport in Molecular-Scale Silicon Nanowire Transistors
We report low-temperature electrical transport studies of molecule-scale
silicon nanowires. Individual nanowires exhibit well-defined Coulomb blockade
oscillations characteristic of charge addition to a single nanostructure with
length scales up to at least 400 nm. Further studies demonstrate coherent
charge transport through discrete single particle quantum levels extending the
whole device, and show that the ground state spin configuration follows the
Lieb-Mattis theorem. In addition, depletion of the nanowires suggests that
phase coherent single-dot characteristics are accessible in a regime where
correlations are strong.Comment: 4 pages and 4 figure
Electron interference and entanglement in coupled 1D systems with noise
We estimate the role of noise in the formation of entanglement and in the
appearance of single- and two-electron interference in systems of coupled
one-dimensional channels semiconductors. Two cases are considered: a
single-particle interferometer and a two-particle interferometer exploiting
Coulomb interaction. In both of them, environmental noise yields a
randomization of the carrier phases. Our results assess how that the
complementarity relation linking single-particle behavior to nonlocal
quantities, such as entanglement and environment-induced decoherence, acts in
electron interferometry. We show that, in a experimental implementation of the
setups examined, one- and two-electron detection probability at the output
drains can be used to evaluate the decoherence phenomena and the degree of
entanglement.Comment: 12 pages, 6 figures. v2: added some references and corrected tex
Quantum Diffusion of H/Ni(111) through the Monte Carlo Wave Function Formalism
We consider a quantum system coupled to a dissipative background with many
degrees of freedom using the Monte Carlo Wave Function method. Instead of
dealing with a density matrix which can be very high-dimensional, the method
consists of integrating a stochastic Schrodinger equation with a non-hermitian
damping term in the evolution operator, and with random quantum jumps. The
method is applied to the diffusion of hydrogen on the Ni(111) surface below 100
K. We show that the recent experimental diffusion data for this system can be
understood through an interband activation process, followed by quantum
tunnelling.Comment: In press at Phys.Rev.Let