68 research outputs found
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 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
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
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
Realisation of the first sub shot noise wide field microscope
In the last years several proof of principle experiments have demonstrated
the advantages of quantum technologies respect to classical schemes. The
present challenge is to overpass the limits of proof of principle
demonstrations to approach real applications. This letter presents such an
achievement in the field of quantum enhanced imaging. In particular, we
describe the realization of a sub-shot noise wide field microscope based on
spatially multi-mode non-classical photon number correlations in twin beams.
The microscope produces real time images of 8000 pixels at full resolution, for
(500micrometers)2 field-of-view, with noise reduced to the 80% of the shot
noise level (for each pixel), suitable for absorption imaging of complex
structures. By fast post-elaboration, specifically applying a quantum enhanced
median filter, the noise can be further reduced (less than 30% of the shot
noise level) by setting a trade-off with the resolution, demonstrating the best
sensitivity per incident photon ever achieved in absorption microscopy.Comment: Light: Science & Applications- Nature in pres
The impact of far-right political orientation and cultural values on conservative attitudes toward life and death in Europe: a multilevel approach
Belief systems are core organizing factors of social attitudes and behaviors, and
their study has highlighted the role of conservatism as a contributing mechanism in
mitigating concerns associated with change avoidance, as well as the reduction of
uncertainty and ambiguity in life. Moreover, these aspects seem to be consistently
used as powerful tools in the political and social discourse of the far-right. Life
and death ethics are an example of issues that deal with the need for stability
and control over personal and social life that people endorsing conservative
values seek to attain. There is a rich line of studies on the individual and social
explanatory factors of political conservatism, but less attention has been dedicated
to moral conservatism as an autonomous and meaningful concept. The current
research follows a multilevel approach to disentangle the individual and contextual
correlates of conservative attitudes toward life and death. Thus, besides looking
at the influence of individual choices related to religion and political orientation,
this study also seeks to analyse the impact of the context, introducing in the
model variables measuring economic performance, social and gender inequality,
religious diversity and the prevalence of materialism and post-materialism values.
Multilevel models using data from the 34 countries that participated in the last
wave of the European Values Study (2017–2020), revealed an association between
far-right orientation and conservative attitudes toward life and death, and that
this relationship is moderated by materialism/post-materialism values, economic
performance, and social inequality. Our findings reinforce the role of democracy
as an environment where freedom of choice and thought are indisputable rights,
cherished by most of the populations, regardless of their political position or their
stance on moral issues.info:eu-repo/semantics/publishedVersio
A quantum model for rf-SQUIDs based metamaterials enabling 3WM and 4WM Travelling Wave Parametric Amplification
A quantum model for Josephson-based metamaterials working in the Three-Wave
Mixing (3WM) and Four-Wave Mixing (4WM) regimes at the single-photon level is
presented. The transmission line taken into account, namely Traveling Wave
Josephson Parametric Amplifier (TWJPA), is a bipole composed by a chain of
rf-SQUIDs which can be biased by a DC current or a magnetic field in order to
activate the 3WM or 4WM nonlinearities. The model exploits a Hamiltonian
approach to analytically determine the time evolution of the system both in the
Heisenberg and interaction pictures. The former returns the analytic form of
the gain of the amplifier, while the latter allows recovering the probability
distributions vs. time of the photonic populations, for multimodal Fock and
coherent input states. The dependence of the metamaterial's nonlinearities is
presented in terms of circuit parameters in a lumped model framework while
evaluating the effects of the experimental conditions on the model validity
Quantifying backflash radiation to prevent zero-error attacks in quantum key distribution
Single-photon avalanche diodes (SPADs) are the most widespread commercial solution for single-photon counting in quantum
key distribution applications. However, the secondary photon emission that arises from the avalanche of charge carriers that
occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the
transmission key. In this paper, we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and
temporal characterization for different detector models and different operating parameters. We qualitatively bound the maximum
information leakage due to backflash light and propose solutions for preventing such leakage
Quantifying backflash radiation to prevent zero-error attacks in quantum key distribution
Single-photon avalanche diodes (SPADs) are the most widespread commercial solution for single-photon counting in quantum key distribution applications. However, the secondary photon emission that arises from the avalanche of charge carriers that occurs during the detection of a photon may be exploited by an eavesdropper to gain information without inducing errors in the transmission key. In this paper, we characterize such backflash light in gated InGaAs/InP SPADs and discuss its spectral and temporal characterization for different detector models and different operating parameters. We qualitatively bound the maximum information leakage due to backflash light and propose solutions for preventing such leakage
Experimental estimation of entanglement at the quantum limit
Entanglement is the central resource of quantum information processing and
the precise characterization of entangled states is a crucial issue for the
development of quantum technologies. This leads to the necessity of a precise,
experimental feasible measure of entanglement. Nevertheless, such measurements
are limited both from experimental uncertainties and intrinsic quantum bounds.
Here we present an experiment where the amount of entanglement of a family of
two-qubit mixed photon states is estimated with the ultimate precision allowed
by quantum mechanics.Comment: 4 pages, 3 figure
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