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1. Emergent complex quantum networks in continuous-variables non-Gaussian states

   Mattia Walschaers, Nicolas Treps (July 2021, ArXivorg)

   Large multipartite quantum systems tend to rapidly reach extraordinary levels of complexity as their number of constituents and entanglement links grow. Here we use complex network theory to study a class of continuous variables quantum states that present both multipartite entanglement and non-Gaussian statistics. In particular, the states are built from an initial imprinted cluster state created via Gaussian entangling operations according to a complex network structure. To go beyond states that can be easily simulated via classical computers we engender non-Gaussian statistics via multiple photon subtraction operations. We then use typical networks measures, the degree and clustering, to characterize the emergent complex network of photon-number correlations after photon subtractions. We show that, in contrast to regular clusters, in the case of imprinted complex network structures the emergent correlations are strongly affected by photon subtraction. On the one hand, we unveil that photon subtraction universally increases the average photon-number correlations, regardless of the imprinted network structure. On the other hand, we show that the shape of the distributions in the emergent networks after subtraction is greatly influenced by the structure of the imprinted network, as witnessed by their higher-moments. Thus for the field of network theory, we introduce a new class of networks to study. At the same time for the field of continuous variable quantum states, this work presents a new set of practical tools to benchmark systems of increasing complexity. 

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2. Controlling Single‐Photon Emission with Ultrathin Transdimensional Plasmonic Films

   https://doi.org/10.1002/andp.202200331  

   Bondarev, Igor V. (October 2022, Annalen der Physik)

   Abstract The properties of a two‐level quantum dipole emitter near an ultrathin transdimensional plasmonic film are studied theoretically. The model system studied mimics a solid‐state single‐photon source device. Using realistic experimental parameters, the spontaneous and stimulated emission intensity profiles are computed as functions of the excitation frequency and film thickness, followed by the analysis of the second‐order photon correlations to explore the photon antibunching effect. It is shown that ultrathin transdimensional plasmonic films can greatly improve photon antibunching with thickness reduction, which allows one to control the quantum properties of light and make them more pronounced. Knowledge of these features is advantageous for solid‐state single‐photon source device engineering and overall for the development of the new integrated quantum photonics material platform based on the transdimensional plasmonic films. 

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3. Multi-tracer intensity mapping: cross-correlations, line noise & decorrelation

   https://doi.org/10.1088/1475-7516/2021/05/068  

   Schaan, Emmanuel; White, Martin (May 2021, Journal of Cosmology and Astroparticle Physics)

   Abstract Line intensity mapping (LIM) is a rapidly emerging technique for constraining cosmology and galaxy formation using multi-frequency, low angular resolution maps.Many LIM applications crucially rely on cross-correlations of two line intensity maps, or of intensity maps with galaxy surveys or galaxy/CMB lensing.We present a consistent halo model to predict all these cross-correlations and enable joint analyses, in 3D redshift-space and for 2D projected maps.We extend the conditional luminosity function formalism to the multi-line case, to consistently account for correlated scatter between multiple galaxy line luminosities.This allows us to model the scale-dependent decorrelation between two line intensity maps,a key input for foreground rejection and for approaches that estimate auto-spectra from cross-spectra.This also enables LIM cross-correlations to reveal astrophysical properties of the interstellar medium inacessible with LIM auto-spectra.We expose the different sources of luminosity scatter or “line noise” in LIM, and clarify their effects on the 1-halo and galaxy shot noise terms.In particular, we show that the effective number density of halos can in some cases exceed that of galaxies, counterintuitively.Using observational and simulation input, we implement this halo model for the Hα, [Oiii], Lyman-α, CO and [Cii] lines.We encourage observers and simulators to measure galaxy luminosity correlation coefficients for pairs of lines whenever possible.Our code is publicly available at https://github.com/EmmanuelSchaan/HaloGen/tree/LIM .In a companion paper, we use this halo model formalism and codeto highlight the degeneracies between cosmology and astrophysics in LIM, and to compare the LIM observables to galaxy detection for a number of surveys. 

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4. Colocalized Sensing and Intelligent Computing in Micro-Sensors

   https://doi.org/10.3390/s20216346  

   H Hasan, Mohammad; Al-Ramini, Ali; Abdel-Rahman, Eihab; Jafari, Roozbeh; Alsaleem, Fadi (November 2020, Sensors)

   null (Ed.)

   This work presents an approach to delay-based reservoir computing (RC) at the sensor level without input modulation. It employs a time-multiplexed bias to maintain transience while utilizing either an electrical signal or an environmental signal (such as acceleration) as an unmodulated input signal. The proposed approach enables RC carried out by sufficiently nonlinear sensory elements, as we demonstrate using a single electrostatically actuated microelectromechanical system (MEMS) device. The MEMS sensor can perform colocalized sensing and computing with fewer electronics than traditional RC elements at the RC input (such as analog-to-digital and digital-to-analog converters). The performance of the MEMS RC is evaluated experimentally using a simple classification task, in which the MEMS device differentiates between the profiles of two signal waveforms. The signal waveforms are chosen to be either electrical waveforms or acceleration waveforms. The classification accuracy of the presented MEMS RC scheme is found to be over 99%. Furthermore, the scheme is found to enable flexible virtual node probing rates, allowing for up to 4× slower probing rates, which relaxes the requirements on the system for reservoir signal sampling. Finally, our experiments show a noise-resistance capability for our MEMS RC scheme. 

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5. Quantifying the enhancement of two-photon absorption due to spectral-temporal entanglement

   https://doi.org/10.1364/OE.422544  

   Landes, Tiemo; Raymer, Michael_G; Allgaier, Markus; Merkouche, Sofiane; Smith, Brian_J; Marcus, Andrew_H (June 2021, Optics Express)

   When a low flux of time-frequency-entangled photon pairs (EPP) illuminates a two-photon transition, the rate of two-photon absorption (TPA) can be enhanced considerably by the quantum nature of photon number correlations and frequency correlations. We use a quantum-theoretic derivation of entangled TPA (ETPA) and calculate an upper bound on the amount of quantum enhancement that is possible in such systems. The derived bounds indicate that in order to observe ETPA the experiments would need to operate at a combination of significantly higher rates of EPP illumination, molecular concentrations, and conventional TPA cross sections than are achieved in typical experiments. 

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