1,002 research outputs found
InN nanowires: Growth and optoelectronic properties
An overview on InN nanowires, fabricated using either a catalyst-free molecular beam epitaxy method or a catalyst assisted chemical vapor deposition process, is provided. Differences and similarities of the nanowires prepared using the two techniques are presented. The present understanding of the growth and of the basic optical and transport properties is discussed
Simulation of charged particle trajectories in the neutron decay correlation experiment abBA
The proposed neutron decay correlation experiment, abBA, will directly detect the direction of emission of decay protons and electrons as well as providing spectroscopic information for both particles. In order to provide this information, the abBA experiment incorporates spatially varying electric and magnetic fields. We report on detailed simulations of the decay particle trajectories in order to assess the impact of various systematic effects on the experimental observables. These include among others; adiabaticity of particle orbits, tracking of orbits, reversal of low energy protons due to inhomogeneous electric field, and accuracy of proton time of flight measurements. Several simulation methods were used including commercial software (Simion), custom software, as well as analytical tools based on the use of adiabatic invariants. Our results indicate that the proposed field geometry of the abBA spectrometer will be substantially immune to most systematic effects and that transport calculations using adiabatic invariants agree well with solution of the full equations of motion
Staying adiabatic with unknown energy gap
We introduce an algorithm to perform an optimal adiabatic evolution that
operates without an apriori knowledge of the system spectrum. By probing the
system gap locally, the algorithm maximizes the evolution speed, thus
minimizing the total evolution time. We test the algorithm on the Landau-Zener
transition and then apply it on the quantum adiabatic computation of 3-SAT: The
result is compatible with an exponential speed-up for up to twenty qubits with
respect to classical algorithms. We finally study a possible algorithm
improvement by combining it with the quantum Zeno effect.Comment: 4 pages, 4 figure
Phase-coherent transport in InN nanowires of various sizes
We investigate phase-coherent transport in InN nanowires of various diameters
and lengths. The nanowires were grown by means of plasma-assisted molecular
beam epitaxy. Information on the phase-coherent transport is gained by
analyzing the characteristic fluctuation pattern in the magneto-conductance.
For a magnetic field oriented parallel to the wire axis we found that the
correlation field mainly depends on the wire cross section, while the
fluctuation amplitude is governed by the wire length. In contrast, if the
magnetic field is oriented perpendicularly, for wires longer than approximately
200 nm the correlation field is limited by the phase coherence length. Further
insight into the orientation dependence of the correlation field is gained by
measuring the conductance fluctuations at various tilt angles of the magnetic
field.Comment: 5 pages, 5 figure
A bosonic Josephson junction controlled by a single trapped ion
We theoretically investigate the properties of a double-well bosonic
Josephson junction coupled to a single trapped ion. We find that the coupling
between the wells can be controlled by the internal state of the ion, which can
be used for studying mesoscopic entanglement between the two systems and to
measure their interaction with high precision. As a particular example we
consider a single Rb atom and a small Bose-Einstein condensate
controlled by a single Yb ion. We calculate inter-well coupling
rates reaching hundreds of Hz, while the state dependence amounts to tens of Hz
for plausible values of the currently unknown s-wave scattering length between
the atom and the ion. The analysis shows that it is possible to induce either
the self-trapping or the tunneling regime, depending on the internal state of
the ion. This enables the generation of large scale ion-atomic wavepacket
entanglement within current technology.Comment: 6 pages and 5 figures, including additional material. Accepted for
publication in Phys. Rev. Let
Room temperature Rydberg Single Photon Source
We present an optimal protocol to implement a room temperature Rydberg single
photon source within an experimental setup based on micro cells filled with
thermal vapor. The optimization of a pulsed four wave mixing scheme allows to
double the effective Rydberg blockade radius as compared to a simple Gaussian
pulse scheme, releasing some of the constrains on the geometry of the micro
cells. The performance of the optimized protocol is improved by about 70% with
respect to the standard protocol.Comment: 5 pages, 6 figure
Two atoms in an anisotropic harmonic trap
We consider the system of two interacting atoms confined in axially symmetric
harmonic trap. Within the pseudopotential approximation, we solve the
Schroedinger equation exactly, discussing the limits of quasi-one and
quasi-two-dimensional geometries. Finally, we discuss the application of an
energy-dependent pseudopotential, which allows to extend the validity of our
results to the case of tight traps and large scattering lengths.Comment: RevTeX 4 pages, 2 figure
Impulsive quantum measurements: restricted path integral versus von Neumann collapse
The relation between the restricted path integral approach to quantum
measurement theory and the commonly accepted von Neumann wavefunction collapse
postulate is presented. It is argued that in the limit of impulsive
measurements the two approaches lead to the same predictions. The example of
repeated impulsive quantum measurements of position performed on a harmonic
oscillator is discussed in detail and the quantum nondemolition strategies are
recovered in both the approaches.Comment: 12 pages, 3 figure
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