222 research outputs found
Tailoring asymmetric lossy channels to test the robustness of mesoscopic quantum states of light
No full textIn the past twenty years many experiments have demonstrated that quantum states of light can be used for secure data transfer, despite the presence of many noise sources. In this paper we investigate, both theoretically and experimentally, the role played by a statistically-distributed asymmetric amount of loss in the degradation of nonclassical photon-number correlations between the two parties of multimode twin-beam states in the mesoscopic intensity regime. To be as close as possible to realistic scenarios, we consider two different statistical distributions of such a loss, a Gaussian distribution and a log-normal one. The results achieved in the two cases show to what extent the involved parameters, both those connected to loss and those describing the employed states of light, preserve nonclassicality
Thermal and superthermal noise signals as resources for underwater quantum communication
No full textQuantum technologies have opened new perspectives for enhancing communication speed and security, particularly in challenging underwater environments, where conventional protocols rely on acoustic wave propagation. In this study, we introduce an innovative communication protocol built upon the utilization of mesoscopic twin-beam (TWB) states, entangled in the number of photons, and photon-number-resolving detectors. Our approach involves transmitting information by mixing the part of TWB that propagates through water with two signals having identical mean values but different statistical distributions. Specifically, we explore the advantages and limitations associated with employing pseudothermal states and two distinct types of superthermal states in our communication protocol. Through both theoretical analysis and experimental investigation, we assess the feasibility of accurately discriminating which state has been superimposed onto the TWB by evaluating the noise reduction factor. Our findings demonstrate promis- ing outcomes, suggesting the practical implementation of this protocol in real-world underwater communication scenarios
Preserving nonclassical correlations in strongly unbalanced conditions
No full textIt is well known that optical losses represent the main obstacle to the real exploitation of quantum optical systems for quantum technology. Here we investigate to what extent the presence of unbalanced losses between the two parties of a mesoscopic twin-beam state can prevent or not the observation of nonclassical correlations. Moreover, we focus on the survival of nonclassicality in the presence of asymmetric lossy channels modeled according to specific statistical distributions
Effect of noisy channels on the transmission of mesoscopic twin-beam states
No full textQuantum properties of light, which are crucial resources for quantum technologies, are quite fragile in nature and can be degraded and even concealed by the environment. We show, both theoretically and experimentally, that mesoscopic twin-beam states of light can preserve their nonclassicality even in the presence of major losses and different types of noise, thus suggesting their potential usefulness to encode information in quantum communication protocols. We develop a comprehensive general analytical model for a measurable nonclassicality criterion and find thresholds on noise and losses for the survival of entanglement in the twin beam
Rainbow correlation imaging with macroscopic twin beam
No full textWe present the implementation of a correlation-imaging protocol that exploits both the spatial and spectral correlations of macroscopic twin-beam states generated by parametric downconversion. In particular, the spectral resolution of an imaging spectrometer coupled to an EMCCD camera is used in a proof-of-principle experiment to encrypt and decrypt a simple code to be transmitted between two parties. In order to optimize the trade-off between visibility and resolution, we provide the characterization of the correlation images as a function of the spatio- spectral properties of twin beams generated at different pump power values
Bracket states for communication protocols with coherent states
No full textWe present the generation and characterization of the class of bracket states, namely phase-sensitive mixtures of coherent states exhibiting symmetry properties in the phase-space de- scription. A bracket state can be seen as the statistical ensemble arriving at a receiver in a typical coherent-state-based communication channel. We show that when a bracket state is mixed at a beam splitter with a local oscillator, both the emerging beams exhibit a Fano factor larger than 1 and dependent on the relative phase between the input state and the local oscil- lator. We discuss the possibility to exploit this dependence to monitor the phase difference for the enhancement of the performances of a simple communication scheme based on direct detection. Our experimental setup involves linear optical elements and a pair of photon-number- resolving detectors operated in the mesoscopic photon-number domain
Generation and detection of mesoscopic pulsed states of light for Quantum Information
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