455 research outputs found

### Factoring and Fourier Transformation with a Mach-Zehnder Interferometer

The scheme of Clauser and Dowling (Phys. Rev. A 53, 4587 (1996)) for
factoring $N$ by means of an N-slit interference experiment is translated into
an experiment with a single Mach-Zehnder interferometer. With dispersive phase
shifters the ratio of the coherence length to wavelength limits the numbers
that can be factored. A conservative estimate permits $N \approx 10^7$. It is
furthermore shown, that sine and cosine Fourier coefficients of a real periodic
function can be obtained with such an interferometer.Comment: 5 pages, 2 postscript figures; to appear in Phys.Rev.A, Nov. 1997;
Figures contained only in replaced versio

### A Few Steps Towards a More Quantitative Understanding of Contrast in the Scanning Electron Microscope

The interaction volume of the electron beam with the specimen in a scanning electron microscope (SEM) is a highly complex function of the surface structure of the specimen, its chemical composition and the energy of the scanning electron beam.· The video signals formed by secondary electrons (SE) or backscattered electrons (BSE) reflect this complexity insofar as they may contain not only information of the interior of the pixel which has just been scanned and its neighborhood, but may depend on surface details hundreds of microns apart from the impinging point of the electron beam. This leads to artifacts in scanning electron micrographs, e.g., edge brightening. The knowledge of the spatial distribution of the current density of the BSE and SE released by the impinging beam are the key for a more quantitative understanding of contrasts in scanning electron micrographs.
In a first step, our emission microscopic method to visualize these distributions has been improved by substituting a photographic registration method by a charged couple device (CCD) densitometer. The resolution of our present densitometer (256 grey levels) is not sufficient to record the full dynamic range of the SE current density distributions. However, this will be possible in the near future with a state of the art CCD-camera and a 14 bit image processing system

### Backscattered Electrons and Their Influence on Contrast in the Scanning Electron Microscope

The backscattered electron (BSE) induced secondaries (SE2) emerge from an area that is usually many orders of magnitude larger than the area in which the impinging primary probe releases secondary electrons (SE1). These SE2 secondary electrons form a) an undesired background signal in high resolution scanning micrographs and b) are responsible for the well known proximity effect in electron beam lithography. In this paper we focus our attention on the first topic exclusively: we discuss the complex influence of the SE2 on contrast in SEM micrographs (neglecting the components SE3 and SE4). We do this on the basis of our emission-microscopic measurements of the spatial distributions of SE1 and SE2 emerging from flat bulk specimens. By integrating these distributions in two dimensions we calculate the total number of SE1 and SE2 electrons and deduce the signal to backgroud ratio SE1/(SE1+SE2), i.e., the maximum contrast in one pixel ( single pixel contrast ) and the contrast of two adjacent pixels 1 and 2 according to its usual definition C= (I1 -I2)/(I1 +I2). We calculate the enhanced secondary emission factor for backscattered electrons from our total numbers of SE1 and SE2 for Si, Ge and Ag to Si=2.58, Ge=1.46, Ag=1,23

### Manifestation of fundamental quantum complementarities in time-domain interference experiments with quantum dots: A theoretical analysis

A theoretical analysis is presented showing that fundamental complementarity
between the particle-like properties of an exciton confined in a semiconductor
quantum dot and the ability of the same system to show interference may be
studied in a time domain interference experiment, similar to those currently
performed. The feasibility of such an experiment, including required pulse
parameters and the dephasing effect of the environment, is studied.Comment: Final, considerably extended version; 8 pages, 3 figure

### MicroSQUID Force microscopy in a dilution refrigerator

We present a new generation of a scanning MicroSQUID microscope operating in
an inverted dilution refrigerator. The MicroSQUIDs have a size of 1.21$ \
\mum\textsuperscript{2} and a magnetic flux sensitivity of 120 \mu\Phi_{0} /
\sqrt{\textrm{Hz}}$and thus a field sensitivity of %$550^{-6} \ \Phi_{0} /
\sqrt{\textrm{Hz}}$550$ \ \mu \textrm{G}/ \sqrt{\textrm{Hz}}$. The scan range
at low temperatures is about 80$\mu$m and a coarse displacement of 5 mm in x
and y direction has been implemented. The MicroSQUID-to-sample distance is
regulated using a tuning fork based force detection. A MicroSQUID-to-sample
distance of 420 nm has been obtained. The reliable knowledge of this distance
is necessary to obtain a trustworthy estimate of the absolute value of the
superconducting penetration depth. An outlook will be given on the ongoing
direction of development

### Hybrid superconducting nanostructures: very low temperature local probing and noise

International audienceWe review the topic of hybrid superconducting nanostructures by introducing the basic physical concepts and describing recent key experimental results. We discuss the superconductivity nucleation in mesoscopic structures, the vortex lattice imaging in doped diamond films, the superconducting proximity effect, multiple Andreev reflection in Josephson junctions and the electronic micro-cooling in hybrid tunnel junctions. An emphasis is put on very low temperature local probes and noise measurement techniques developed in Grenoble

### Silicon Superconducting Quantum Interference Device

We have studied a Superconducting Quantum Interference SQUID device made from
a single layer thin film of superconducting silicon. The superconducting layer
is obtained by heavily doping a silicon wafer with boron atoms using the Gas
Immersion Laser Doping (GILD) technique. The SQUID device is composed of two
nano-bridges (Dayem bridges) in a loop and shows magnetic flux modulation at
low temperature and low magnetic field. The overall behavior shows very good
agreement with numerical simulations based on the Ginzburg-Landau equations.Comment: Published in Applied Physics Letters (August 2015

### Observation of vortex coalescence in the anisotropic spin-triplet superconductor Sr$_{2}$RuO$_{4}$

We present direct imaging of magnetic flux structures in the anisotropic,
spin-triplet superconductor Sr$_{2}$RuO$_{4}$ using a scanning $\mu$SQUID
microscope. Individual quantized vortices were seen at low magnetic fields.
Coalescing vortices forming flux domains were revealed at intermediate fields.
Based on our observations we suggest that a mechanism intrinsic to the material
stabilizes the flux domains against the repulsive vortex-vortex interaction.
Topological defects like domain walls can provide this, implying proof for
unconventional chiral superconductivity.Comment: submitted to PR

### General relativistic corrections to the Sagnac effect

The difference in travel time of corotating and counter-rotating light waves
in the field of a central massive and spinning body is studied. The corrections
to the special relativistic formula are worked out in a Kerr field. Estimation
of numeric values for the Earth and satellites in orbit around it show that a
direct measurement is in the order of concrete possibilities.Comment: REVTex, accepted for publication on Phys. Rev.

### Nonlocality, Bell's Ansatz and Probability

Quantum Mechanics lacks an intuitive interpretation, which is the cause of a
generally formalistic approach to its use. This in turn has led to a certain
insensitivity to the actual meaning of many words used in its description and
interpretation. Herein, we analyze carefully the possible mathematical meanings
of those terms used in analysis of EPR's contention, that Quantum Mechanics is
incomplete, as well as Bell's work descendant therefrom. As a result, many
inconsistencies and errors in contemporary discussions of nonlocality, as well
as in Bell's Ansatz with respect to the laws of probability, are identified.
Evading these errors precludes serious conflicts between Quantum Mechanics and
both Special Relativity and Philosophy.Comment: 8&1/2 pages revtex; v2: many corrections, clairifications &
extentions, all small; v3: editorial scru

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