72 research outputs found
Electron interferometry with nano-gratings
We present an electron interferometer based on near-field diffraction from
two nanostructure gratings. Lau fringes are observed with an imaging detector,
and revivals in the fringe visibility occur as the separation between gratings
is increased from 0 to 3 mm. This verifies that electron beams diffracted by
nanostructures remain coherent after propagating farther than the Talbot length
= 1.2 mm, and hence is a proof of principle for the
function of a Talbot-Lau interferometer for electrons. Distorted fringes due to
a phase object demonstrates an application for this new type of electron
interferometer.Comment: 4 pgs, 6 figure
Image transmission through a stable paraxial cavity
We study the transmission of a monochromatic "image" through a paraxial
cavity. Using the formalism of self-transform functions, we show that a
transverse degenerate cavity transmits the self-transform part of the image,
with respect to the field transformation over one round-trip of the cavity.
This formalism gives a new insight on the understanding of the behavior of a
transverse degenerate cavity, complementary to the transverse mode picture. An
experiment of image transmission through a hemiconfocal cavity show the
interest of this approach.Comment: submitted to Phys. Rev.
Moir\'e patterns in quantum images
We observed moir\'e fringes in spatial quantum correlations between twin
photons generated by parametric down-conversion. Spatially periodic structures
were nonlocally superposed giving rise to beat frequencies typical of moir\'e
patterns. This result brings interesting perspectives regarding metrological
applications of such a quantum optical setup.Comment: 4 pages, 5 figure
An electron Talbot interferometer
The Talbot effect, in which a wave imprinted with transverse periodicity
reconstructs itself at regular intervals, is a diffraction phenomenon that
occurs in many physical systems. Here we present the first observation of the
Talbot effect for electron de Broglie waves behind a nanofabricated
transmission grating. This was thought to be difficult because of Coulomb
interactions between electrons and nanostructure gratings, yet we were able to
map out the entire near-field interference pattern, the "Talbot carpet", behind
a grating. We did this using a Talbot interferometer, in which Talbot
interference fringes from one grating are moire'-filtered by a 2nd grating.
This arrangement has served for optical, X-ray, and atom interferometry, but
never before for electrons. Talbot interferometers are particularly sensitive
to distortions of the incident wavefronts, and to illustrate this we used our
Talbot interferometer to measure the wavefront curvature of a weakly focused
electron beam. Here we report how this wavefront curvature demagnified the
Talbot revivals, and we discuss applications for electron Talbot
interferometers.Comment: 5 pages, 5 figures, updated version with abstrac
Factorization of Numbers with the temporal Talbot effect: Optical implementation by a sequence of shaped ultrashort pulses
We report on the successful operation of an analogue computer designed to
factor numbers. Our device relies solely on the interference of classical light
and brings together the field of ultrashort laser pulses with number theory.
Indeed, the frequency component of the electric field corresponding to a
sequence of appropriately shaped femtosecond pulses is determined by a Gauss
sum which allows us to find the factors of a number
Talbot effect in cylindrical waveguides
We extend the theory of Talbot revivals for planar or rectangular geometry to
the case of cylindrical waveguides. We derive a list of conditions that are
necessary to obtain revivals in cylindrical waveguides. A phase space approach
based on the Wigner and the Kirkwood-Rihaczek functions provides a pictorial
representation of TM modes interference associated with the Talbot effect
The wave nature of biomolecules and fluorofullerenes
We demonstrate quantum interference for tetraphenylporphyrin, the first
biomolecule exhibiting wave nature, and for the fluorofullerene C60F48 using a
near-field Talbot-Lau interferometer. For the porphyrins, which are
distinguished by their low symmetry and their abundant occurence in organic
systems, we find the theoretically expected maximal interference contrast and
its expected dependence on the de Broglie wavelength. For C60F48 the observed
fringe visibility is below the expected value, but the high contrast still
provides good evidence for the quantum character of the observed fringe
pattern. The fluorofullerenes therefore set the new mark in complexity and mass
(1632 amu) for de Broglie wave experiments, exceeding the previous mass record
by a factor of two.Comment: 5 pages, 4 figure
Theory of decoherence in a matter wave Talbot-Lau interferometer
We present a theoretical framework to describe the effects of decoherence on
matter waves in Talbot-Lau interferometry. Using a Wigner description of the
stationary beam the loss of interference contrast can be calculated in closed
form. The formulation includes both the decohering coupling to the environment
and the coherent interaction with the grating walls. It facilitates the
quantitative distinction of genuine quantum interference from the expectations
of classical mechanics. We provide realistic microscopic descriptions of the
experimentally relevant interactions in terms of the bulk properties of the
particles and show that the treatment is equivalent to solving the
corresponding master equation in paraxial approximation.Comment: 20 pages, 4 figures (minor corrections; now in two-column format
Decoherence of matter waves by thermal emission of radiation
Emergent quantum technologies have led to increasing interest in decoherence
- the processes that limit the appearance of quantum effects and turn them into
classical phenomena. One important cause of decoherence is the interaction of a
quantum system with its environment, which 'entangles' the two and distributes
the quantum coherence over so many degrees of freedom as to render it
unobservable. Decoherence theory has been complemented by experiments using
matter waves coupled to external photons or molecules, and by investigations
using coherent photon states, trapped ions and electron interferometers. Large
molecules are particularly suitable for the investigation of the
quantum-classical transition because they can store much energy in numerous
internal degrees of freedom; the internal energy can be converted into thermal
radiation and thus induce decoherence. Here we report matter wave
interferometer experiments in which C70 molecules lose their quantum behaviour
by thermal emission of radiation. We find good quantitative agreement between
our experimental observations and microscopic decoherence theory. Decoherence
by emission of thermal radiation is a general mechanism that should be relevant
to all macroscopic bodies.Comment: 5 pages, 4 figure
- âŠ