Randomized Benchmarking for Individual Quantum Gates

Any technology requires precise benchmarking of its components, and the quantum technologies are no exception. Randomized benchmarking allows for the relatively resource economical estimation of the average gate fidelity of quantum gates from the Clifford group, assuming identical noise levels for all gates, making use of suitable sequences of randomly chosen Clifford gates. In this work, we report significant progress on randomized benchmarking, by showing that it can be done for individual quantum gates outside the Clifford group, even for varying noise levels per quantum gate. This is possible at little overhead of quantum resources, but at the expense of a significant classical computational cost. At the heart of our analysis is a representation-theoretic framework that we develop here which is brought into contact with classical estimation techniques based on bootstrapping and matrix pencils. We demonstrate the functioning of the scheme at hand of benchmarking tensor powers of T-gates. Apart from its practical relevance, we expect this insight to be relevant as it highlights the role of assumptions made on unknown noise processes when characterizing quantum gates at high precision.Comment: 4+13 pages, 4 figures, small changes, references adde

Development of a CFD methodology for fuel-air mixing and combustion modeling of GDI Engines

Simulation of GDI engines represents a very challenging task for CFD modeling. In particular, many sub-models are involved since the evolution of the fuel spray and liquid film formation should be modeled. Furthermore, it is necessary to account for both the influence of mixture and flow conditions close to the spark plug to correctly predict the flame propagation process. In this work, the authors developed a CFD methodology to study the air-fuel mixing and combustion processes in direct-injection, spark-ignition engines. A set of sub-models was developed to describe injection, atomization, breakup and wall impingement for sprays emerging from multi-hole atomizers. Furthermore, the complete evolution of the liquid fuel film was described by solving its mass, energy and momentum equations on the cylinderw wall boundaries. To model combustion, the Extended Coherent Flamelet Model (ECFM) was used in combination with a Lagrangian ignition model, describing the evolution of the flame kernel and accounting for both for flow, mixture composition and properties of the electrical circuit. The proposed approach has been implemented into the Lib-ICE code, which is based on the OpenFOAMR technology. In this paper, examples of application are provided, including the simulation of the fuel-air mixing process in a real GDI engine and the prediction of the premixed turbulent combustion process in a constant-volume vessel for different operating conditions

VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors

[EN] The paper describes the development in the OpenFOAM® technology of a dynamic multiphase Volume-of-Fluid (VoF) solver, supporting mesh handling with topological changes, that has been used for the study of the physics of the primary jet breakup and of the flow disturbance induced by the nozzle geometry during the injector opening event in high-pressure Gasoline Direct Injection (GDI) engines. Turbulence modeling based on a scale-resolving approach has been applied, while phase change of fuel is accounted by means of a cavitation model that has been coupled with the VOF solver. Simulations have been carried out on a 6-hole prototype injector, especially developed for investigations in the framework of the collaborative project FUI MAGIE and provided by Continental Automotive SAS. Special attention has been paid to the domain decomposition strategy and to the code development of the solver, to ensure good load balancing and to minimize inter-processor communication, to achieve good performance and also high scalability on large computing clusters.Giussani, F.; Montorfano, A.; Piscaglia, F.; Onorati, A.; Helie, J. (2017). VOF Simulation of The Cavitating Flow in High Pressure GDI Injectors. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 1009-1018. https://doi.org/10.4995/ILASS2017.2017.4989OCS1009101

A quasi 3D approach for the modelling of an automotive turbocharger's compressor

In this work the 3DCell method has been extended to the thermo-fluid dynamic simulation of an automotive turbocharger's compressor. The 3DCell, an approach continuously developed by the authors at Politecnico di Milano, is based on a pseudo-staggered leapfrog method that allows to decompose a generic 3D problem in a set of 1D scalar equation arbitrarily oriented in space. The system of equations has been solved referring to a relative rotating framework for the moving components, whereas to an absolute reference elsewhere. The domain has been discretized on a basis of a polar coordinate system, identifying five macro sub-domains, namely the inlet pipe, impeller, vaneless diffuser, volute, outlet pipe, each treated numerically in a specific way. The diffuser's momentum in the tangential direction has been modelled resorting to the conservation of the angular momentum, while the rotor channels are modelled as rotating pipes that exchange work and momentum with the blades as they experience a relative source term due to the centrifugal force field and its potential. The model has been validated against measurements carried out on a steady state flow test bench at University of Genoa

Anthropic pressures on Nature 2000 Sites: recommendations and monitoring criteria for the pollution emergency response activities within the Orbetello lagoon

L’elevato valore naturalistico e socioeconomico di un Sito Natura 2000 richiede che tutte le attività antropiche che si svolgono al suo interno (es. pesca, turismo, trasporti, attività industriali, etc.) siano gestite in maniera tale da non pregiudicare le specie e gli habitat per i quali l’area è stata designata. Molti di questi Siti sono ambienti di transizione, ovvero zone che costituiscono il passaggio naturale tra terra e mare. La loro posizione di interfaccia tra questi due ambienti li rende ecosistemi unici e biologicamente molto produttivi, sede di meccanismi di regolazione dei processi interattivi della biosfera nelle due fasi, terrestre e marina. In alcuni Siti la presenza di attività antropiche diffuse e prolungate nel tempo ha portato al riscontro di stati di contaminazione elevata, fino all’inclusione di queste zone, o parti di esse, tra i Siti di bonifica di Interesse Nazionale (SIN). Il presente lavoro descrive le linee di indirizzo e le attività di monitoraggio da attuare per la salvaguardia della salute pubblica e dell’ambiente nel corso degli interventi di messa in sicurezza di emergenza predisposti nell’area lagunare antistante l’area industriale Ex Sitoco, all’interno della perimetrazione del SIN di Orbetello, incluso in un Sito di Importanza Comunitaria. Le matrici ambientali potenzialmente a rischio a causa dell’esecuzione di tali interventi sono: acqua, sedimento, biocenosi acquatiche, avifauna, uomo. È altresì importante valutare gli effetti che le ipotetiche modifiche su microscala, apportate a livello di ogni matrice, potrebbero causare nel lungo periodo su macroscala.The high naturalistic and socio-economic value of Natura 2000 sites requires that all human activities performed within their borders (e.g. fishing, tourism, transports, industrial activities) are regulated. Indeed, the site management should assure the effective safeguard of all species and habitats of European interest included in the protected area. A lot of such sites are located in transitional environments, that are areas characterised by a natural progression from the terrestrial to the water environments. Such environments include unique and very productive habitats, and they represent the regulation mechanisms of the interactive processes of the terrestrial and marine biosphere. In some sites, the presence of human activities that are distributed both in space and time has led to high levels of contamination, that in some cases even required their inclusion in Reclamation Sites of National Interest (SIN). The present study describes the planning and monitoring activities to be performed in order to safeguard human and environment health during the actions of MISE in the lagoonal area in front of the industrial area Ex Sitoco, within the borders of the Orbetello SIN, included in a SCI. The environmental parameters that are potentially at risk due to such activities are: water, sediment, water biocenosis, birds, humans. Furthermore, it is important to evaluate the effects that potential variations at the microscale level may cause at the macroscale level

Direct evaluation of turbine isentropic efficiency in turbochargers: Cfd assisted design of an innovative measuring technique

Turbocharging is playing today a fundamental role not only to improve automotive engine performance, but also to reduce fuel consumption and exhaust emissions for both Spark Ignition and Diesel engines. Dedicated experimental investigations on turbochargers are therefore necessary to assess a better understanding of its performance. The availability of experimental information on turbocharger steady flow performance is an essential requirement to optimize the engine-turbocharger matching, which is usually achieved by means of simulation models. This aspect is even more important when referred to the turbine efficiency, since its swallowing capacity can be accurately evaluated through the measurement of mass flow rate, inlet temperature and pressure ratio across the machine. However, in the case of a turbocharger radial inflow turbine, isentropic efficiency, directly evaluated starting from measurement of thermodynamic parameters at the inlet and outlet sections, can give significant errors. This inaccuracy is mainly related to the difficulty of a correct evaluation of the turbine outlet temperature due to the non-uniform distribution of flow field and temperature at the measuring section. This work is the follow up of a previous publication where an intensive measurement campaign was performed to obtain a reliable measurement of the turbine outlet temperature. To this aim, a hand-made 3-hole probe (unlike most of the measuring probes available on the market, which are considered as intrusive ) was adopted to perform measurement of the flow field, pressure and temperature downstream the turbine with special reference to different radial and tangential positions in two sections located near and far from the outlet machine, allowing the evaluation of the efficiency through local enthalpy fluxes across the turbine in cold and hot conditions upstream the turbine. The comparison between results obtained through the local measurements and those achieved through a direct measurement of turbine outlet temperature by three probes inserted in pipe with a different protrusion, have highlighted that heat transfer effects across the pipes and across the turbocharger components play an important role on the estimation of temperature profile at the outlet section. In order to put some light on this aspect, CFD simulations have been performed to estimate the impact of the heat transfer and flow distribution on the estimation of the isentropic efficiency. The OpenFOAM\uae code has been adopted to simulate the actual turbine geometry resorting to multi reference frame (MRF) strategies, instead of mesh motion strategies, to characterize the flow pattern downstream of the turbine. Moreover, CFD analysis was used to design a specific device, whose goal was the dissipation of flow structures dominated by vorticity, achieving in this way a uniform distribution of the flow and temperature fields at the measuring section. This will result in a much more reliable evaluation of the turbine efficienc