14,428 research outputs found
Single-particle-sensitive imaging of freely propagating ultracold atoms
We present a novel imaging system for ultracold quantum gases in expansion.
After release from a confining potential, atoms fall through a sheet of
resonant excitation laser light and the emitted fluorescence photons are imaged
onto an amplified CCD camera using a high numerical aperture optical system.
The imaging system reaches an extraordinary dynamic range, not attainable with
conventional absorption imaging. We demonstrate single-atom detection for
dilute atomic clouds with high efficiency where at the same time dense
Bose-Einstein condensates can be imaged without saturation or distortion. The
spatial resolution can reach the sampling limit as given by the 8 \mu m pixel
size in object space. Pulsed operation of the detector allows for slice images,
a first step toward a 3D tomography of the measured object. The scheme can
easily be implemented for any atomic species and all optical components are
situated outside the vacuum system. As a first application we perform
thermometry on rubidium Bose-Einstein condensates created on an atom chip.Comment: 24 pages, 10 figures. v2: as publishe
Adaptive polarimetric image representation for contrast optimization of a polarized beacon through fog
We present a contrast-maximizing optimal linear representation of
polarimetric images obtained from a snapshot polarimetric camera for enhanced
vision of a polarized light source in obscured weather conditions (fog, haze,
cloud) over long distances (above 1 km). We quantitatively compare the gain in
contrast obtained by different linear representations of the experimental
polarimetric images taken during rapidly varying foggy conditions. It is shown
that the adaptive image representation that depends on the correlation in
background noise fluctuations in the two polarimetric images provides an
optimal contrast enhancement over all weather conditions as opposed to a simple
difference image which underperforms during low visibility conditions. Finally,
we derive the analytic expression of the gain in contrast obtained with this
optimal representation and show that the experimental results are in agreement
with the assumed correlated Gaussian noise model
Photon number correlation for quantum enhanced imaging and sensing
In this review we present the potentialities and the achievements of the use
of non-classical photon number correlations in twin beams (TWB) states for many
applications, ranging from imaging to metrology. Photon number correlations in
the quantum regime are easy to be produced and are rather robust against
unavoidable experimental losses, and noise in some cases, if compared to the
entanglement, where loosing one photon can completely compromise the state and
its exploitable advantage. Here, we will focus on quantum enhanced protocols in
which only phase-insensitive intensity measurements (photon number counting)
are performed, which allow probing transmission/absorption properties of a
system, leading for example to innovative target detection schemes in a strong
background. In this framework, one of the advantages is that the sources
experimentally available emit a wide number of pairwise correlated modes, which
can be intercepted and exploited separately, for example by many pixels of a
camera, providing a parallelism, essential in several applications, like wide
field sub-shot-noise imaging and quantum enhanced ghost imaging. Finally,
non-classical correlation enables new possibilities in quantum radiometry, e.g.
the possibility of absolute calibration of a spatial resolving detector from
the on-off- single photon regime to the linear regime, in the same setup
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