94 research outputs found
Spectral Vector Beams for High-Speed Spectroscopic Measurements
Structured light harnessing multiple degrees of freedom has become a powerful
approach to use complex states of light in fundamental studies and
applications. Here, we investigate the light field of an ultrafast laser beam
with a wavelength-depended polarization state, a beam we term spectral vector
beam. We demonstrate a simple technique to generate and tune such structured
beams and demonstrate their spectroscopic capabilities. By only measuring the
polarization state using fast photodetectors, it is possible to track
pulse-to-pulse changes in the frequency spectrum caused by, e.g. narrowband
transmission or absorption. In our experiments, we reach read-out rates of
around 6 MHz, which is limited by our technical ability to modulate the
spectrum and can in principle reach GHz read-out rates. In simulations we
extend the spectral range to more than 1000 nm by using a supercontinuum light
source, thereby paving the way to various applications requiring high-speed
spectroscopic measurements.Comment: 11 pages, 12 figure
Deterministic Ultracold Ion Source targeting the Heisenberg Limit
The major challenges to fabricate quantum processors and future nano solid
state devices are material modification techniques with nanometre resolution
and suppression of statistical fluctuations of dopants or qubit carriers. Based
on a segmented ion trap with mK laser cooled ions we have realized a
deterministic single ion source which could operate with a huge range of
sympathetically cooled ion species, isotopes or ionic molecules. We have
deterministically extracted a predetermined number of ions on demand and have
measured a longitudinal velocity uncertainty of 6.3m/s and a spatial beam
divergence of 0.6 mrad. We show in numerical simulations that if the ions are
cooled to the motional ground state (Heisenberg limit) nanometre spatial
resolution can be achieved.Comment: 4 pages 4 figures. to be published in pr
Sensing rotations with multiplane light conversion
We report an experiment estimating the three parameters of a general
rotation. The scheme uses quantum states attaining the ultimate precision
dictated by the quantum Cram\'er-Rao bound. We realize the states
experimentally using the orbital angular momentum of light and implement the
rotations with a multiplane light conversion setup, which allows one to perform
arbitrary unitary transformations on a finite set of spatial modes. The
observed performance suggests a range of potential applications in the next
generation of rotation sensors.Comment: 8 pages, 4 figures. Comments welcome! arXiv admin note: text overlap
with arXiv:2012.0059
Relational Particle Models. II. Use as toy models for quantum geometrodynamics
Relational particle models are employed as toy models for the study of the
Problem of Time in quantum geometrodynamics. These models' analogue of the thin
sandwich is resolved. It is argued that the relative configuration space and
shape space of these models are close analogues from various perspectives of
superspace and conformal superspace respectively. The geometry of these spaces
and quantization thereupon is presented. A quantity that is frozen in the scale
invariant relational particle model is demonstrated to be an internal time in a
certain portion of the relational particle reformulation of Newtonian
mechanics. The semiclassical approach for these models is studied as an
emergent time resolution for these models, as are consistent records
approaches.Comment: Replaced with published version. Minor changes only; 1 reference
correcte
Triangleland. I. Classical dynamics with exchange of relative angular momentum
In Euclidean relational particle mechanics, only relative times, relative
angles and relative separations are meaningful. Barbour--Bertotti (1982) theory
is of this form and can be viewed as a recovery of (a portion of) Newtonian
mechanics from relational premises. This is of interest in the absolute versus
relative motion debate and also shares a number of features with the
geometrodynamical formulation of general relativity, making it suitable for
some modelling of the problem of time in quantum gravity. I also study
similarity relational particle mechanics (`dynamics of pure shape'), in which
only relative times, relative angles and {\sl ratios of} relative separations
are meaningful. This I consider firstly as it is simpler, particularly in 1 and
2 d, for which the configuration space geometry turns out to be well-known,
e.g. S^2 for the `triangleland' (3-particle) case that I consider in detail.
Secondly, the similarity model occurs as a sub-model within the Euclidean
model: that admits a shape--scale split. For harmonic oscillator like
potentials, similarity triangleland model turns out to have the same
mathematics as a family of rigid rotor problems, while the Euclidean case turns
out to have parallels with the Kepler--Coulomb problem in spherical and
parabolic coordinates. Previous work on relational mechanics covered cases
where the constituent subsystems do not exchange relative angular momentum,
which is a simplifying (but in some ways undesirable) feature paralleling
centrality in ordinary mechanics. In this paper I lift this restriction. In
each case I reduce the relational problem to a standard one, thus obtain
various exact, asymptotic and numerical solutions, and then recast these into
the original mechanical variables for physical interpretation.Comment: Journal Reference added, minor updates to References and Figure
Measurements in two bases are sufficient for certifying high-dimensional entanglement
High-dimensional encoding of quantum information provides a promising method
of transcending current limitations in quantum communication. One of the
central challenges in the pursuit of such an approach is the certification of
high-dimensional entanglement. In particular, it is desirable to do so without
resorting to inefficient full state tomography. Here, we show how carefully
constructed measurements in two bases (one of which is not orthonormal) can be
used to faithfully and efficiently certify bipartite high-dimensional states
and their entanglement for any physical platform. To showcase the practicality
of this approach under realistic conditions, we put it to the test for photons
entangled in their orbital angular momentum. In our experimental setup, we are
able to verify 9-dimensional entanglement for a pair of photons on a
11-dimensional subspace each, at present the highest amount certified without
any assumptions on the state.Comment: 11+14 pages, 2+7 figure
Foundations of Relational Particle Dynamics
Relational particle dynamics include the dynamics of pure shape and cases in
which absolute scale or absolute rotation are additionally meaningful. These
are interesting as regards the absolute versus relative motion debate as well
as discussion of conceptual issues connected with the problem of time in
quantum gravity. In spatial dimension 1 and 2 the relative configuration spaces
of shapes are n-spheres and complex projective spaces, from which knowledge I
construct natural mechanics on these spaces. I also show that these coincide
with Barbour's indirectly-constructed relational dynamics by performing a full
reduction on the latter. Then the identification of the configuration spaces as
n-spheres and complex projective spaces, for which spaces much mathematics is
available, significantly advances the understanding of Barbour's relational
theory in spatial dimensions 1 and 2. I also provide the parallel study of a
new theory for which positon and scale are purely relative but orientation is
absolute. The configuration space for this is an n-sphere regardless of the
spatial dimension, which renders this theory a more tractable arena for
investigation of implications of scale invariance than Barbour's theory itself.Comment: Minor typos corrected; references update
Causal structures and causal boundaries
We give an up-to-date perspective with a general overview of the theory of
causal properties, the derived causal structures, their classification and
applications, and the definition and construction of causal boundaries and of
causal symmetries, mostly for Lorentzian manifolds but also in more abstract
settings.Comment: Final version. To appear in Classical and Quantum Gravit
Modal beam splitter:Determination of the transversal components of an electromagnetic light field
The transversal profile of beams can always be defined as a superposition of orthogonal fields, such as optical eigenmodes. Here, we describe a generic method to separate the individual components in a laser beam and map each mode onto its designated detector with low crosstalk. We demonstrate this with the decomposition into Laguerre-Gaussian beams and introduce a distribution over the integer numbers corresponding to the discrete orbital and radial momentum components of the light field. The method is based on determining an eigenmask filter transforming the incident optical eigenmodes to position eigenmodes enabling the detection of the state of the light field using single detectors while minimizing cross talk with respect to the set of filter masks considered.UK Engineering and Physical Sciences Research Council [EP/J01771X/1]This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
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