No abstract

We derive a family of stochastic master equations describing homodyne measurement of multi-qubit diagonal observables in circuit quantum electrodynamics. In the regime where qubit decay can be neglected, our approach replaces the polaron-like transformation of previous work, which required a lengthy calculation for the physically interesting case of three qubits and two resonator modes. The technique introduced here makes this calculation straightforward and manifestly correct. Using this technique, we are able to show that registers larger than one qubit evolve under a non-Markovian master equation. We perform numerical simulations of the three-qubit, two-mode case from previous work, obtaining an average post-measurement state fidelity of ∼94%, limited by measurement-induced decoherence and dephasing.

The new possibilities offered by additive manufacturing (AM) can be exploited in gas turbines to produce a new generation of complex and efficient internal coolant systems. The flexibility offered by this new manufacturing method needs a paradigm shift in the design approach, and a possible solution is offered by topology optimization. The overall goal of this work is to propose an innovative method to design internal channels in gas turbines that fully exploit AM capabilities. The present work contains a new application of a fluid topology sedimentation method to optimize the internal coolant geometries with minimal pressure losses while maximizing the heat exchange. The domain is considered as a porous medium with variable porosity: the solution is represented by the final solid distribution that constitutes the optimized structure. In this work, the governing equations for an incompressible flow in a porous medium are considered together with a conjugate heat transfer equation that includes porosity-dependent thermal diffusivity. An adjoint optimization approach with steepest descent method is used to build the optimization algorithm. The simulations are carried out on three different geometries: a U-bend, a straight duct, and a rectangular box. For the U-bend, a series of splitter is automatically generated by the code, minimizing the stagnation pressure losses. In the straight duct and in the rectangular box, the impact of different choices of the weights and of the definition of the porosity-dependent thermal diffusivity is analyzed. The results show the formation of splitters and bifurcations in the box and “riblike” structures in the straight duct, which enhance the heat transfer.

We consider how the Hamiltonian Quantum Computing scheme introduced in [New Journal of Physics, vol. 18, p. 023042, 2016] can be implemented using a 2D array of superconducting transmon qubits. We show how the scheme requires the engineering of strong attractive cross-Kerr and weak flip-flop or hopping interactions and we detail how this can be achieved. Our proposal uses a new electric circuit for obtaining the attractive cross-Kerr coupling between transmons via a dipolelike element. We discuss and numerically analyze the forward motion and execution of the computation and its dependence on coupling strengths and their variability. We extend [New Journal of Physics, vol. 18, p. 023042, 2016] by explicitly showing how to construct a direct Toffoli gate, thus establishing computational universality via the Hadamard and Toffoli gate or via controlled-Hadamard, Hadamard and CNOT.arXiv:1812.00454v3 [quant-ph]

We consider the direct three-qubit parity measurement scheme with two measurement resonators, using circuit quantum electrodynamics to analyze its functioning for several different types of superconducting qubits. We find that for the most common, transmon-like qubit, the presence of additional qubit-state-dependent coupling terms of the two resonators hinders the possibility of performing the direct parity measurement. We show how this problem can be solved by employing the tunable coupling qubit (TCQ) in a particular designed configuration. In this case, we effectively engineer the original model Hamiltonian by canceling the harmful terms. We further develop an analysis of the measurement in terms of information gains and provide some estimates of the typical parameters for optimal operation with TCQs.

No abstract

Gas turbine design has been characterized over the years by a continuous increase of the maximum cycle temperature, justified by a corresponding increase of cycle efficiency and power output. In such way turbine components heat load management has become a compulsory activity and then, a reliable procedure to evaluate the blades and vanes metal temperatures, is, nowadays, a crucial aspect for a safe components design. This two part work presents a three-dimensional conjugate heat transfer procedure developed in the framework of an internal research project of GE Oil & Gas. The procedure, applied to the first rotor blade of the MS5002E gas turbine, consists in a decoupled analysis in which the internal cooling system was modeled by an in-house one dimensional thermo-fluid network solver, the external heat loads and pressure distribution have been evaluated through 3D CFD and the heat conduction in the solid is carried out through a 3D FEM solution. The second part of this work is focused on the improvement of external heat loads prediction through the use of a full featured geometry of the blade. In particular a detailed representation of the rim seal is accounted for as well as the actual geometry of the squealer tip. A new set of conjugate results is compared with temperature obtained by metallographic analysis, pointing out the relevant effect of the actual endwall contour on the metal temperature distribution at low spans of the blade.

Gas turbine design has been characterized over the years by a continuous increase of the maximum cycle temperature, justified by a corresponding increase of cycle efficiency and power output. In such way turbine components heat load management has become a compulsory activity and then, a reliable procedure to evaluate the blades and vanes metal temperatures, is, nowadays, a crucial aspect for a safe components design. This two part work presents a three-dimensional conjugate heat transfer procedure developed in the framework of an internal research project of GE Oil & Gas. The procedure, applied to the first rotor blade of the MS5002E gas turbine, consists of a conjugate heat transfer analysis in which the internal cooling system was modeled by an in-house one dimensional thermo-fluid network solver, the external heat loads and pressure distribution have been evaluated through 3D CFD and the heat conduction in the solid is carried out through a 3D FEM solution. The first part of this work is focused on the description of the procedures in terms of set up of the equivalent fluid network model of internal cooling system and its tuning through experimental measurements of blade flow function. A first computation of blade metal temperature was obtained by coupling with CFD computations carried out on a de-featured geometry of the blade. Achieved results are compared with the data of a metallographic analysis performed on a blade operated on an actual engine. Some discrepancies are observed between datasets, suggesting the necessity to improve the models, mainly from the CFD side.