1,721,052 research outputs found
Mesoscopic States of Light for the Detection of Weakly Absorbing Objects
Full text linkOver 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
Towards underwater quantum communication in the mesoscopic intensity regime
Full text linkThe 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
Ghost imaging by intense multimode twin beam
No full textWe present the first experimental implementation of the ghost-imaging protocol based on an intense multimode spontaneous parametric down-conversion process. Temporal and spatial properties of the quantum field used in the protocol are also discussed
Direct detection of super-thermal photon-number statistics in second-harmonic generation
No full textChanges in the statistical properties of light undergoing second-harmonic generation are investigated in the photon- number-resolving domain. We theoretically demonstrate that when a portion of multimode thermal light produced by parametric down-conversion is up-converted, both the second-harmonics and the residual beam at the fundamental wavelength are endowed with super-thermal photon-number distributions. The experimental results, which were obtained by exploiting the photo-numberresolving capability of hybrid photodetectors, are in excellent agreement with the theoretical expectations
Multi-mode twin-beam states in the mesoscopic intensity domain
No full textParametric down conversion is a quantum nonlinear process of paramount importance in the Quantum Optics context since it produces entangled states of light. Such states, usually called twin-beam (TWB) states, exhibit perfect correlations in many degrees of freedom, among which the number of photons. In this review paper, we focus on their generation and characterization in the rather unusual mesoscopic intensity regime. The use of photon-number-resolving detectors allows the experimental reconstruction of the statistical properties of TWB states and the demonstration of their nonclassical nature. This characterization is preliminary and necessary in view of the application of TWB states to the development of Quantum Technologies. In this work we focus on the robustness of mesoscopic TWB states against losses and noise sources for their exploitation in the field of Quantum Communication
Statistics of twin-beam states by photon-number resolving detectors up to pump depletion
No full textWe use hybrid photodetectors endowed with partial photon-number resolution to characterize the photon-number distribution of twin-beam states produced at different intensity regimes up to pump depletion. To match the detectors’ dynamics, the light of signal and idler is strongly attenuated by neutral-density filters. Since the filters do not modify the nature of any classical-light statistics, we find that signal and idler are described by a multimode thermal distribution at any pump power. The number of modes decreases at increasing pump power until pump depletion, when the number starts increasing again. The effect is qualitatively interpreted as a selective mode amplification induced by the high-gain parametric process
Novel scheme for secure data transmission based on mesoscopic twin beams and photon-number-resolving detectors
Full text linkQuantum 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
Autocorrelation functions: a useful tool for both state and detector characterisation
Full text linkThe calculation of autocorrelation functions represents a routinely used tool to characterise quantum states of light. In this paper, we evaluate the g(2) function for detected photons in the case of mesoscopic multi-mode twin-beam states in order to fully investigate their statistical properties starting from measurable quantities. Moreover, we show that the second-order autocorrelation function is also useful to estimate the spurious effects affecting the employed Silicon-photomultiplier detectors
Photon-number correlations by photon-number resolving detectors
No full textWe demonstrate that by using pairs of photodetectors endowed with internal gain we are able to quantify the photon-number correlation coefficient between the two components of a pulsed bipartite state in the "mesoscopic" intensity regime (less than 100 mean photons). We compare the performances of hybrid photoemissive detectors to those of multipixel silicon photon counters and demonstrate that the absence of significant noise allows the evaluation of the variance of the distribution of the differences in photon numbers, and hence of the shot-noise level, without any correction
Self-consistent phase determination for Wigner function reconstruction
No full textWe present the reconstruction of the Wigner function of a classical phase-sensitive state, a pulsed coherent state, by measurements of the distributions of detected-photons of the state displaced by a coherent probe field. By using a hybrid photodetector operated above its photon-resolving regime, we obtain both the statistics at different values of the probe field and the values of the probe phase required to reconstruct the Wigner function
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