404 research outputs found
Photon-number correlations by photon-number resolving detectors
We demonstrate that by using a pair of photodetectors endowed with internal
gain we are able to quantify the correlation coefficient between the two
components of a pulsed bipartite state in the mesoscopic intensity regime (less
than 100 mean photons)
Photon statistics in the macroscopic realm measured without photon-counters
In a macroscopic realm, in which photons are too many for being counted by
any photon counting detector, photon statistics can be measured by using
detectors simply endowed with linear response. We insert one of such detectors
in a conventional photon-counting apparatus, which returns a voltage every time
the detector responds to light by generating a number of elementary charges via
its primary photo-detection process. We only assume that, when a single charge
is photo-generated, the probability density of the voltages is a distribution
that is narrow with respect to its mean value. Under this hypothesis the output
voltages can be suitably binned so that their probability distribution is the
same as that of the photo-generated charges, that is, of the detected photons
Chaotic imaging in frequency downconversion
We analyze and realize the recovery, by means of spatial intensity
correlations, of the image obtained by a seeded frequency downconversion
process in which the seed field is chaotic and an intensity modulation is
encoded on the pump field. Although the generated field is as chaotic as the
seed field and does not carry any information about the modulation of the pump,
an image of the pump can be extracted by measuring the spatial intensity
correlations between the generated field and one Fourier component of the seed
Reliable source of conditional non-Gaussian states from single-mode thermal fields
We address both theoretically and experimentally the generation of pulsed
non-Gaussian states from classical Gaussian ones by means of conditional
measurements. The setup relies on a beam splitter and a pair of linear
photodetectors able to resolve up to tens of photons in the two outputs. We
show the reliability of the setup and the good agreement with the theory for a
single-mode thermal field entering the beam splitter and present a thorough
characterization of the photon statistics of the conditional states.Comment: 18 pages, 12 figure
Gaussian and Non-Gaussian operations on non-Gaussian state: engineering non-Gaussianity
Multiple photon subtraction applied to a displaced phase-averaged coherent
state, which is a non-Gaussian classical state, produces conditional states
with a non trivial (positive) Glauber-Sudarshan -representation. We
theoretically and experimentally demonstrate that, despite its simplicity, this
class of conditional states cannot be fully characterized by direct detection
of photon numbers. In particular, the non-Gaussianity of the state is a
characteristics that must be assessed by phase-sensitive measurements. We also
show that the non-Gaussianity of conditional states can be manipulated by
choosing suitable conditioning values and composition of phase-averaged states
Experimental quantification of non-Gaussianity of phase-randomized coherent states
We present the experimental investigation of the non-Gaussian nature of some
mixtures of Fock states by reconstructing their Wigner function and exploiting
two recently introduced measures of non-Gaussianity. In particular, we
demonstrate the consistency between the different approaches and the
monotonicity of the two measures for states belonging to the class of phase
randomized coherent states. Moreover, we prove that the exact behavior of one
measure with respect to the other depends on the states under investigation and
devise possible criteria to discriminate which measure is more useful for the
characterization of the states in realistic applications.Comment: 9 pages, 4 figure
Photon-number statistics with Silicon photomultipliers
We present a description of the operation of a multi-pixel detector in the
presence of non-negligible dark-count and cross-talk effects. We apply the
model to devise self-consistent calibration strategies to be performed on the
very light under investigation
Homodyne-like detection for state-discrimination in the presence of phase noise
We propose an innovative strategy to discriminate between two coherent states
affected by either uniform or gaussian phase noise. The strategy is based on a
homodyne-like detection scheme with photon-number-resolving detectors in the
regime of low-intensity local oscillator. The experimental implementation of
the detection scheme involves two hybrid photodetectors, whose outputs are used
in post processing to calculate the shot-by-shot photon-number difference. The
performance of this strategy is quantified in terms of the error probability in
discriminating the noisy coherent signals as a function of the characteristic
noise parameters.Comment: 5 pages, 5 figure
Towards underwater quantum communication in the mesoscopic intensity regime
The problem of secure underwater communication can take advantage of the exploitation of quantum resources and novel quantum technologies. At variance with the current experiments performed at the single photon level, here we propose a different scenario involving mesoscopic twin-beam states of light and two classes of commercial photon-number-resolving detectors. We prove that twin-beam states remain nonclassical even if the signal propagates in tubes filled with water, while the idler is transmitted in free space. We also demonstrate that from the study of the nonclassicality information about the loss and noise sources affecting the transmission channels can be successfully extracted
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