1,720,977 research outputs found
Development of a Superconducting Platform for the Manipulation of Quantum States in the Microwave Regime
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Internal reflections and nonlinear effects interplay in non-ideal JTWPA
No full textThe paper investigates the interplay of nonlinear effects with the non-ideal transmission properties of a Josephson Travelling Wave Parametric Amplifier (JTWPA). Experimental characterization using a microwave and DC cryogenic setup reveals periodic transmission modulation linked to the tuning of the Josephson inductances embedded in the line. The effects of impedance matching and resonant parametric down-conversion (PDC) are observed on a broadband scale, and the impact of design parameters and fabrication issues on device performance is analyzed. These findings contribute to the optimizing techniques for JTWPA devices, advancing quantum-limited amplifiers
Superconducting Josephson - Based Metamaterials for Quantum - Limited Parametric Amplification: A Review
Full text linkIn the last few years, several groups have proposed and developed their own platforms demonstrating quantum-limited linear parametric amplification, with evident applications in quantum information and computation, electrical and optical metrology, radio astronomy, and basic physics concerning axion detection. Here, we propose a short review on the physics behind parametric amplification via metamaterials composed by coplanar waveguides embedding several Josephson junctions. We present and compare different schemes that exploit the nonlinearity of the Josephson current-phase relation to mix the so-called signal, idler, and pump tones. The chapter then presents and compares three different theoretical models, developed in the last few years, to predict the dynamics of these nonlinear systems in the particular case of a 4-wave mixing process and under the degenerate undepleted pump assumption. We will demonstrate that, under the same assumption, all the results are comparable in terms of amplification of the output fields
Josephson Traveling Wave Parametric Amplifier as Quantum Source of Entangled Photons for Microwave Quantum Radar Applications
Full text linkJosephson Traveling Wave Parametric Amplifier (JTWPA) has the potential to offer quantum limited noise and a large bandwidth. This amplifier is based on parametric amplification of microwaves traveling through a transmission line with embedded non-linear elements. In this paper, starting from the fabrication of the JTWPA, based on Quantum Electrodynamics (QEDs), operating as a non-classical quantum source for generating a signal-idler entangled state, its characterization in terms of scattering parameters is presented. The cryogenic and room temperature experimental results are discussed. The good performance of the JTWPA in terms of wide bandwidth and increased transmitted power makes it an ideal candidate for Microwave Quantum Radar (MQR) applications. Finally, the performance of an MQR based on the JTWPA developed at INRiM is reported, showing a radar maximum range equal to 82.2 m, which represents a greater value than previously published works
A pragmatic approach to evaluate alternative indicators to GDP
Full text linkThe serious economic crisis broken out in 2008 highly stressed the limitations of GDP used as a well-being indicator and as a predictive tool for economy. This induced the need to identify new indicators able to link the economic prosperity of a country to aspects of sustainable development and externalities, both positive and negative, in the long run. The aim of this paper is to introduce a structured approach which supports the choice or the construction of alternative indicators to GDP. The starting point is the definition of what a well-being indicator actually should represent according to the Recommendations of the Stiglitz-Sen-Fitoussi Report on the measurement of economic performance and social progress. Then the paper introduces a systematic procedure for the analysis of well-being indicators. The different phases of this procedure entail the checking of indicators technical properties and their effect on the representational efficacy. Finally, some of the most representative well-being indicators drawn from the literature are compared and a detailed application example is propose
Flux pumping of Cooper pairs through a Josephson Energy-Suppression Pump
Full text linkIn this paper, we propose a novel kind of Josephson Energy Suppression Pump (JESP) controlled by a fully magnetic flux drive. The device presented here is composed of two superconducting loops interrupted at one side by superconducting nanowires which are joined together by a superconducting island. The phase difference developed at the edges of the nanowires by means of the magnetic flux threading the loops can collapse
their Cooper condensates, leading to complete suppression of the Josephson energies. This mechanism allows to greatly reduce the leakage current when performing Cooper pair pumping by a pure magnetic pumping cycle without involving any gate modulation. The pumping capability of the JESP is studied through a master equation approach in the non-adiabatic case
Quantum model for rf-SQUID-based metamaterials enabling three-wave mixing and four-wave mixing traveling-wave parametric amplification
Full text linkA quantum model for Josephson-based metamaterials working in the three-wave mixing (3WM) and four-wave mixing (4WM) regimes at the single-photon level is presented. The transmission line taken into account, namely Josephson traveling wave parametric amplifier (JTWPA), is a bipole composed of a chain of rf-SQUIDs, which can be biased by a DC current or a magnetic field to activate the 3WM or 4WM nonlinearities. The model exploits a Hamiltonian approach to analytically determine the time evolution of the system both in the Heisenberg and interaction pictures. The former returns the analytic form of the gain of the amplifier, while the latter allows recovering the probability distributions vs time of the photonic populations, for multimodal Fock and coherent input states. The dependence of the metamaterial’s nonlinearities is presented in terms of circuit parameters in a lumped model framework while evaluating the effects of the experimental conditions on the model validity
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Magnetic Flux Sensing Exploiting Two SQUIPTs Connected by means of a Floating Island
Full text linkMagnetometers exploiting interference effect of the superconducting wavefunction are known since the realization of the first SQUID, with several improvements in performance in the following years. In this field, the Superconducting Quantum Interference Proximity Transistor (SQUIPT) offers an interesting alternative to the conventional SQUID thanks to its lower power dissipation that makes it ideal for nanoscale and ultra-low temperature (T<1 mK) applications, where very low dissipation is required. Here, a device composed of two facing fully superconducting SQUIPT is proposed. Numerical simulations demonstrate how the interplay between the behaviours of a couple of tunnel junctions in such a design accounts for promising performances as both a flux-to-current and a flux-to-voltage transducer
- …
