147 research outputs found
Experimental Quantum Imaging exploiting multi-mode spatial correlation of twin beams
Properties of quantum states have disclosed new and revolutionary
technologies, ranging from quantum information to quantum imaging. This last
field is addressed to overcome limits of classical imaging by exploiting
specific properties of quantum states of light. One of the most interesting
proposed scheme exploits spatial quantum correlations between twin beams for
realizing sub-shot-noise imaging of the weak absorbing objects, leading ideally
to a noise-free imaging. Here we discuss in detail the experimental realization
of this scheme, showing its capability to reach a larger signal to noise ratio
with respect to classical imaging methods and, therefore, its interest for
future practical applications
Quantum Enhanced Imaging of Non-Uniform Refractive Profiles
In this work quantum metrology techniques are applied to the imaging of
objects with a non-uniform refractive spatial profile. A sensible improvement
on the classical accuracy is shown to be found when the "Twin Beam State" (TWB)
is used. In particular exploiting the multimode spatial correlation, naturally
produced in the Parametric Down Conversion (PDC) process, allows a 2D
reconstruction of complex spatial profiles, thus enabling an enhanced imaging.
The idea is to use one of the spatially multimode beam to probe the sample and
the other as a reference to reduce the noise. A similar model can be also used
to describe wave front distortion measurements. The model is meant to be
followed by a first experimental demonstration of such enhanced measurement
scheme
Unbiased estimation of an optical loss at the ultimate quantum limit with twin-beams
Loss measurements are at the base of spectroscopy and imaging, thus perme-
ating all the branches of science, from chemistry and biology to physics and
material science. However, quantum mechanics laws set the ultimate limit to the
sensitivity, constrained by the probe mean energy. This can be the main source
of uncertainty, for example when dealing with delicate system such as
biological samples or photosensitive chemicals. It turns out that ordinary
(clas- sical) probe beams, namely with Poissonian photon number distribution,
are fundamentally inadequate to measure small losses with the highest
sensitivity. Conversely, we demonstrate that a quantum-correlated pair of
beams, known as twin-beam state, allows reaching the ultimate sensitivity for
all energy regimes (even less than one photon per mode) with the simplest
measurement strategy. One beam of the pair addresses the sample, while the
second one is used as a reference to compensate both for classical drifts and
for uctuation at the most fundamental quantum level. This scheme is also
absolute and accurate, since it self-compensates for unavoidable instability of
the sources and detectors, which could otherwise lead to strongly biased
results. Moreover, we report the best sensitivity per photon ever achieved in
loss estimation experiments
Quantum enhanced imaging of nonuniform refractive profiles
In this work, quantum metrology techniques are applied to the imaging of objects with a nonuniform refractive spatial profile. A sensible improvement on the classical accuracy is shown to be found when the "Twin Beam (TWB) State" is used. In particular, exploiting the multimode spatial correlation, naturally produced in the Parametric Down Conversion (PDC) process, allows a 2D reconstruction of complex spatial profiles, thus enabling an enhanced imaging. The idea is to use one of the spatially multimode beams to probe the sample and the other as a reference to reduce the noise. A similar model can also be used to describe wave front distortion measurements. The model is meant to be followed by a first experimental demonstration of such enhanced measurement scheme
Systematic analysis of SNR in bipartite Ghost Imaging with classical and quantum light
We present a complete and exhaustive theory of signal-to-noise-ratio in
bipartite ghost imaging with classical (thermal) and quantum (twin beams)
light. The theory is compared with experiment for both twin beams and thermal
light in a certain regime of interest
Quantum differential ghost microscopy
Quantum correlations become formidable tools for beating classical capacities
of measurement. Preserving these advantages in practical systems, where
experimental imperfections are unavoidable, is a challenge of the utmost
importance. Here we propose and realize a quantum ghost imaging protocol able
to compensate for the detrimental effect of detection noise and losses. This
represents an important improvement as quantum correlations allow low
brightness imaging, desirable for reducing the absorption dose. In particular,
we develop a comprehensive model starting from a ghost imaging scheme
elaborated for bright thermal light, known as differential ghost imaging and
particularly suitable in the relevant case of faint or sparse objects. We
perform the experiment using SPDC light in microscopic configuration. The image
is reconstructed exploiting non-classical intensity correlation rather than
photon pairs detection coincidences. On one side we validate the theoretical
model and on the other we show the applicability of this technique by
reconstructing a biological object with 5 micrometers resolution
Single-phase and correlated-phase estimation with multiphoton annihilated squeezed vacuum states: An energy-balancing scenario
partially_open3In recent years, several works have demonstrated the advantage of photon-subtracted Gaussian states for various quantum optics and information protocols. In most of these works, the relation between the advantages and the usual increasing energy of the quantum state related to photon subtraction was not clearly investigated. In this paper, we study the performance of an interferometer injected with multiphoton-annihilated squeezed vacuum states mixed with coherent states for both single- and correlated-phase estimations. For single-phase estimation, although the use of multiphoton-annihilated squeezed vacuum states at low mean photons per mode provides an advantage compared to classical strategy, when the total input energy is held fixed, the advantage due to photon subtraction is completely lost. However, for the correlated case in the analogous scenario, some advantage appears to come from both the energy rise and improvement in photon statistics. In particular quantum enhanced sensitivity with photon-subtracted states appears more robust to losses, showing an advantage of about 30% with respect to the squeezed vacuum state in the case of a realistic value of the detection efficiency.openN. Samantaray; I. Ruo Berchera; I. P. DegiovanniSamantaray, N.; Ruo Berchera, I.; Degiovanni, I. P
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