82 research outputs found
Mesoscopic States of Light for the Detection of Weakly Absorbing Objects
Over the past twenty years, different imaging techniques have been proposed and implemented in order to reconstruct the images of different kinds of objects, including faint ones. In this work, we exploit the mesoscopic intensity domain to prove that the determination of the transmittance efficiency of an object can be obtained by considering the calculation of the noise reduction factor in the case of a multi-mode pseudothermal state divided at a balanced beam splitter and detected by photon-number-resolving detectors. The good quality of the experimental results suggests that this strategy can be extended to the determination of a matrix of different transmittance values by means of arrays of photon-number-resolving detectors
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
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
Novel scheme for secure data transmission based on mesoscopic twin beams and photon-number-resolving detectors
Quantum resources can improve the quality and security of data transmission. A novel communication protocol based on the use of mesoscopic twin-beam (TWB) states of light is proposed and discussed. The message sent by Alice to Bob is encoded in binary single-mode thermal states having two possible mean values, both smaller than the mean value of the TWB. Such thermal states are alternately superimposed to the portion of TWB sent to Bob. We demonstrate that in the presence of an eavesdropping attack that intercepts and substitutes part of the signal with a thermal noise, Bob can still successfully decrypt the message by evaluating the noise reduction factor for detected photons. The protocol opens new perspectives in the exploitation of quantum states of light for applications to Quantum Communication
Absolute calibration of photon-number-resolving detectors with an analog output using twin beams
A method for absolute calibration of a photon-number resolving detector
producing analog signals as the output is developed using a twin beam. The
method gives both analog-to-digital conversion parameters and quantum detection
efficiency for the photon fields. Characteristics of the used twin beam are
also obtained. A simplified variant of the method applicable to fields with
high signal to noise ratios and suitable for more intense twin beams is
suggested.Comment: 4 pages, 3 figure
Characterization of phase-averaged coherent states
We present the full characterization of phase-randomized or phase-averaged
coherent states, a class of states exploited in communication channels and in
decoy state-based quantum key distribution protocols. In particular, we report
on the suitable formalism to analytically describe the main features of this
class of states and on their experimental investigation, that results in
agreement with theory. We also show the results we obtained by manipulating the
phase-averaged coherent states with linear optical elements and testify their
good quality by employing some non-Gaussianity measures and the concept of
mutual information.Comment: 15 pages, 11 figure
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