2,481 research outputs found
Quantum dephasing and decay of classical correlation functions in chaotic systems
We discuss the dephasing induced by the internal classical chaotic motion in
the absence of any external environment. To this end we consider a suitable
extension of fidelity for mixed states which is measurable in a Ramsey
interferometry experiment. We then relate the dephasing to the decay of this
quantity which, in the semiclassical limit, is expressed in terms of an
appropriate classical correlation function. Our results are derived
analytically for the example of a nonlinear driven oscillator and then
numerically confirmed for the kicked rotor model.Comment: 14 pages, 1 figur
Complexity of Quantum States and Reversibility of Quantum Motion
We present a quantitative analysis of the reversibility properties of
classically chaotic quantum motion. We analyze the connection between
reversibility and the rate at which a quantum state acquires a more and more
complicated structure in its time evolution. This complexity is characterized
by the number of harmonics of the (initially isotropic, i.e.
) Wigner function, which are generated during quantum evolution
for the time . We show that, in contrast to the classical exponential
increase, this number can grow not faster than linearly and then relate this
fact with the degree of reversibility of the quantum motion. To explore the
reversibility we reverse the quantum evolution at some moment immediately
after applying at this moment an instant perturbation governed by a strength
parameter . It follows that there exists a critical perturbation strength,
, below which the initial state is well
recovered, whereas reversibility disappears when . In the
classical limit the number of harmonics proliferates exponentially with time
and the motion becomes practically irreversible. The above results are
illustrated in the example of the kicked quartic oscillator model.Comment: 15 pages, 13 figures; the list of references is update
Correlation plenoptic imaging
Plenoptic imaging is a promising optical modality that simultaneously
captures the location and the propagation direction of light in order to enable
three-dimensional imaging in a single shot. However, in classical imaging
systems, the maximum spatial and angular resolutions are fundamentally linked;
thereby, the maximum achievable depth of field is inversely proportional to the
spatial resolution. We propose to take advantage of the second-order
correlation properties of light to overcome this fundamental limitation. In
this paper, we demonstrate that the momentum/position correlation of chaotic
light leads to the enhanced refocusing power of correlation plenoptic imaging
with respect to standard plenoptic imaging.Comment: 6 pages, 3 figure
The observed chemical structure of L1544
Prior to star formation, pre-stellar cores accumulate matter towards the
centre. As a consequence, their central density increases while the temperature
decreases. Understanding the evolution of the chemistry and physics in this
early phase is crucial to study the processes governing the formation of a
star. We aim at studying the chemical differentiation of a prototypical
pre-stellar core, L1544, by detailed molecular maps. In contrast with single
pointing observations, we performed a deep study on the dependencies of
chemistry on physical and external conditions. We present the emission maps of
39 different molecular transitions belonging to 22 different molecules in the
central 6.25 arcmin of L1544. We classified our sample in five families,
depending on the location of their emission peaks within the core. Furthermore,
to systematically study the correlations among different molecules, we have
performed the principal component analysis (PCA) on the integrated emission
maps. The PCA allows us to reduce the amount of variables in our dataset.
Finally, we compare the maps of the first three principal components with the
H column density map, and the T map of the core. The results of
our qualitative analysis is the classification of the molecules in our dataset
in the following groups: (i) the -CH family (carbon chain
molecules), (ii) the dust peak family (nitrogen-bearing species), (iii) the
methanol peak family (oxygen-bearing molecules), (iv) the HNCO peak family
(HNCO, propyne and its deuterated isotopologues). Only HCO and
CS do not belong to any of the above mentioned groups. The principal
component maps allow us to confirm the (anti-)correlations among different
families that were described in a first qualitative analysis, but also points
out the correlation that could not be inferred before.Comment: 29 pages, 19 figures, 2 appendices, accepted for publication in A&A,
arXiv abstract has been slightly modifie
Exploring plenoptic properties of correlation imaging with chaotic light
In a setup illuminated by chaotic light, we consider different schemes that
enable to perform imaging by measuring second-order intensity correlations. The
most relevant feature of the proposed protocols is the ability to perform
plenoptic imaging, namely to reconstruct the geometrical path of light
propagating in the system, by imaging both the object and the focusing element.
This property allows to encode, in a single data acquisition, both
multi-perspective images of the scene and light distribution in different
planes between the scene and the focusing element. We unveil the plenoptic
property of three different setups, explore their refocusing potentialities and
discuss their practical applications.Comment: 9 pages, 4 figure
Correlation Plenoptic Imaging With Entangled Photons
Plenoptic imaging is a novel optical technique for three-dimensional imaging
in a single shot. It is enabled by the simultaneous measurement of both the
location and the propagation direction of light in a given scene. In the
standard approach, the maximum spatial and angular resolutions are inversely
proportional, and so are the resolution and the maximum achievable depth of
focus of the 3D image. We have recently proposed a method to overcome such
fundamental limits by combining plenoptic imaging with an intriguing
correlation remote-imaging technique: ghost imaging. Here, we theoretically
demonstrate that correlation plenoptic imaging can be effectively achieved by
exploiting the position-momentum entanglement characterizing spontaneous
parametric down-conversion (SPDC) photon pairs. As a proof-of-principle
demonstration, we shall show that correlation plenoptic imaging with entangled
photons may enable the refocusing of an out-of-focus image at the same depth of
focus of a standard plenoptic device, but without sacrificing
diffraction-limited image resolution.Comment: 12 pages, 5 figure
Dynamics of entanglement in quantum computers with imperfections
The dynamics of the pairwise entanglement in a qubit lattice in the presence
of static imperfections exhibits different regimes. We show that there is a
transition from a perturbative region, where the entanglement is stable against
imperfections, to the ergodic regime, in which a pair of qubits becomes
entangled with the rest of the lattice and the pairwise entanglement drops to
zero. The transition is almost independent of the size of the quantum computer.
We consider both the case of an initial maximally entangled and separable
state. In this last case there is a broad crossover region in which the
computer imperfections can be used to create a significant amount of pairwise
entanglement.Comment: 4 pages, 4 figure
Diffraction-limited plenoptic imaging with correlated light
Traditional optical imaging faces an unavoidable trade-off between resolution
and depth of field (DOF). To increase resolution, high numerical apertures (NA)
are needed, but the associated large angular uncertainty results in a limited
range of depths that can be put in sharp focus. Plenoptic imaging was
introduced a few years ago to remedy this trade off. To this aim, plenoptic
imaging reconstructs the path of light rays from the lens to the sensor.
However, the improvement offered by standard plenoptic imaging is practical and
not fundamental: the increased DOF leads to a proportional reduction of the
resolution well above the diffraction limit imposed by the lens NA. In this
paper, we demonstrate that correlation measurements enable pushing plenoptic
imaging to its fundamental limits of both resolution and DOF. Namely, we
demonstrate to maintain the imaging resolution at the diffraction limit while
increasing the depth of field by a factor of 7. Our results represent the
theoretical and experimental basis for the effective development of the
promising applications of plenoptic imaging.Comment: 10 pages, 10 figure
Values we learn from our parents influence our trust in others with money and business
New research sheds light on what determines trust, a key element of economic activity, write Jeffrey V. Butler, Paola Giuliano and Luigi Guis
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