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المؤلفون: George Vahala, Min Soe, Linda Vahala, Abhay K. Ram
مصطلحات موضوعية: Physics, Electromagnetic wave propagation, maxwell equations, Quantum Information Science, Qubit lattice algorithm, scattering of waves
الوصف: Long-time quantum lattice algorithm (QLA) simulations are performed for the multiple reflection-transmission of an initial electromagnetic pulse propagating normally to a boundary layer region joining two media of different refractive index. For these one-dimensional (1D) simulations, there is excellent agreement between x-, y- and z-representations, as well as very good agreement with nearly all the standard plane wave boundary condition results for reflection and transmission off a dielectric discontinuity. In the QLA simulation, no boundary conditions are imposed at the continuous, but sharply increasing, dielectric boundary layers. Two-dimensional (2D) QLA scattering simulations in the x–z plane are performed for an electromagnetic pulse interacting with a conical dielectric obstacle for the 8–16 qubit model.
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المؤلفون: Efstratios Koukoutsis, Kyriakos Hizanidis, Abhay K. Ram
مصطلحات موضوعية: Physics, maxwell equations, Quantum Computing, Quantum Information Science, Schrodinger equation, wave propagation in plasma
الوصف: Quantum computing (QC) has shown enormous promise for solving classes of problems for which a quantum algorithm can obtain a speedup (advantage) over the classical counterpart. Such a speed up would be extremely desirable to be exploited in favor of classical,high demanding in computational resources, simulations of electromagnetic wave propagation in plasma. We propose a formalism, appropriate for application of Quantum Computation methods in plasma electromagnetic wave propagation, based on the Schrodinger representation of Maxwell Equations for a cold, homogeneous, collision-less, two species magnetized plasma. The "quantal" electromagnetic picture retains all the attributes of classical theory whereas provides new insights in the framework of plasma electrodynamics as well as to other quantum-based descriptions.
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المؤلفون: George Vahala, John Hawthorne, Linda Vahala, Abhay K. Ram, Min Soe
مصطلحات موضوعية: Physics, Electromagnetic wave propagation, maxwell equations, Quantum Computing, Quantum Information Science, Qubit lattice algorithm
الوصف: A quantum lattice representation (QLA) is devised for the initial value problem of one-dimensional (1D) propagation of an electromagnetic disturbance in a scalar dielectric medium satisfying directly only the two curl equations of Maxwell. It si found that only 4 qubits/node are required. The collision, streaming, and potential operators are determined so as to recover the two curl equations to second order. Both polarizations are considered.
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المؤلفون: Efstratios Koukoutsis, Kyriakos Hizanidis, Abhay K. Ram, George Vahala
مصطلحات موضوعية: Physics, Dissipative-dispersive media, Electromagnetic wave propagation, maxwell equations, Quantum Computing, Quantum Information Science
الوصف: The dissipative character of an electromagnetic medium breaks the unitary evolution structure that is present in lossless, dispersive optical media. In dispersive media, dissipation appears in the Schrodinger representation of Maxwell equations as a sparse diagonal operator occupying an r-dimensional subspace. A first order Suzuki-Trotter approximation for the evolution operator enables us to isolate the non-unitary operators (associated with dissipation) from the unitary operators (associated with lossless media). The unitary operators can be implemented through qubit lattice algorithm (QLA) on n qubits, based on the discretization and the dimensionality of the pertinent fields. However, the non-unitary-dissipative part poses a challenge both physically and computationally on how it should be implemented on a quantum computer. In this paper, two dilation algorithms are considered for handling the dissipative operators. The first algorithm is based on treating the classical dissipation as a linear amplitude damping-type completely positive trace preserving (CPTP) quantum channel where an unspecified environment interacts with the system of interest and produces the non-unitary evolution. Therefore, the combined system-environment is now closed, and must undergo unitary evolution in the dilated space. The unspecified environment can be modeled by just one ancillary qubit, resulting in an implementation scaling of O(2n−1n2) elementary gates for the total system-environment unitary evolution operator. The second algorithm approximates the non-unitary operators by the Linear Combination of Unitaries (LCU). On exploiting the diagonal structure of the dissipation, we obtain an optimized representation of the non-unitary part, which requires O(2n) elementary gates. A connection of our results with the non-linear-in-normalization-only (NINO) quantum channels is also presented.
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المؤلفون: Zhai, X.M., Chen, J.L., Xiang, N., Bonoli, P.T., Shiraiwa, S.
مصطلحات موضوعية: Physics, EAST launching waves, electron distribution functions, flux surfaces, frequency 2.45 GHz, frequency 4.6 GHz, injected wave power, Landau damping, long pulse discharges, low density plasmas, lower hybrid current drive, Lower Hybrid waves, magnetic shear reversal configuration, phase space analysis, ray-tracing Fokker-Planck simulations, wave propagation domains
الوصف: Lower hybrid current drive (LHCD) is one of the major approaches maintaining long pulse discharges on EAST. There are two lower hybrid (LH) systems on EAST launching waves at 4.6 GHz and 2.45 GHz into the plasma, respectively, and the input power of the 4.6 GHz wave is typically dominant. In this work, the synergy of the two waves and the modification of the power deposition of the 4.6 GHz wave by coupling the 2.45 GHz wave are investigated theoretically. According to the phase space analysis, the wave propagation domains of the two LH waves always overlap substantially with each other for typical LHCD experimental parameters on EAST, indicating that the coupling between them might be strong. Ray-tracing/Fokker-Planck simulations for a LH current drive experiment on EAST show that the change of the power deposition profile due to the coupling could be understood by the rise and fall of the tails of the parallel electron distribution functions on different flux surfaces. If either the injected wave power at 2.45 GHz is comparable with that at 4.6 GHz or the incident N|| of the 2.45 GHz wave reaches a high value (e.g., 5:7/[sqrt(Te(0)]), the power deposition profile of the 4.6GHz wave can be modified greatly due to the coupling with the 2.45 GHz wave. With the parameters compatible with the ability of the LH wave system on EAST, injection of the 2.45 GHz wave can still modify the power deposition profile of the 4.6 GHz wave significantly by combining those two approaches. Finally, it is shown how a 4.6 GHz wave which cannot be Landau damped when injected alone is absorbed in low density plasmas with a magnetic shear reversal configuration in the presence of a 2.45 GHz wave.
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المؤلفون: George Vahala, Linda Vahala, Min Soe, Abhay K. Ram
مصطلحات موضوعية: Physics, Electromagnetic wave propagation, Gaussian pulse propagation, Maxwell's equations, Quantum Information Science, Quantum Lattice Algorithms
الوصف: A three-dimensional quantum lattice algorithm (QLA) for electromagnetic wave propagation is being developed by stitching together the individual QLAs for 1D wave propagation in the three orthogonal Cartesian directions.
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المؤلفون: A.K. Ram, Z. Ioannidis, K. Hizanidis, S.-I. Valvis, A. Papadopoulos, A. Zisis, I. Tigelis
مصطلحات موضوعية: Physics, diffraction reflection and refraction of waves, RF current drive, RF heating, RF wave propagation, scattering of waves by turbulence
الوصف: The practical and economic viability of tokamak fusion reactors depends, in a significant way, on the efficiency of radio frequency (RF) waves to deliver energy and momentum to the plasma in the core of the reactor. Among the various attributes of RF waves is their ability to heat magnetically confined plasmas, induce plasma currents in an effort to achieve steady state, and modify the current profile so as to control plasma instabilities like the neoclassical tearing modes. The RF electromagnetic waves, excited by antenna structures placed near the wall of a tokamak, have to propagate through the turbulent plasma in the scrape-off layer (SOL) along their path to the core plasma. While the propagation and damping of RF waves in the core is reasonably well understood, the same is not true for RF propagation through the SOL. In present day fusion devices, the radial width of the SOL is of the order of a few centimeters. In ITER and in future fusion reactors this width will be of the order of tens of centimeters. Any deleterious effects on RF waves due to plasma turbulence in the SOL has to be properly understood in order to optimize the delivery of RF energy and momentum into the core. This paper is on a multi-pronged approach that is being pursued to quantify the effect of SOL plasma on RF waves. The SOL is composed of coherent filamentary, or blob like, structures and incoherent fluctuations. For coherent structures a full-wave theoretical model has been developed. This model is used to benchmark computational codes that are subsequently used to study general distribution of filaments, thereby extending the range of the theoretical formulation. For incoherent fluctuations, a common approach towards quantifying the effects of turbulence is the Kirchhoff technique. This technique is based on physical optics and the wave fields at any point on a spatially varying surface are approximated to be the same as the fields on a tangent plane at that point. The results from the theoretical analysis are compared with ...
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المؤلفون: George Vahala, Min Soe, Linda Vahala, Abhay K. Ram
مصطلحات موضوعية: Physics, Electromagnetic wave propagation, electtromagneti wave scattering, Quantum Computing, Quantum Information Science, quantum lattice algorithm
الوصف: Long time quantum lattice algorithm (QLA) simulations are performed for the mul- tiple reflection-transmission of an initial electromagnetic pulse propagating normally to a boundary layer region joining two media of different refractive index. For these one dimensional (1D) sim- ulations, there is excellent agreement between x-, y- and z- representations, as well as very good agreement with nearly all the standard plane wave boundary condition results for reflection and transmission off a dielectric discontinuity. In the QLA simulation, no boundary conditions are im- posed at the continuous, but sharply increasing, dielectic boundary layers. Two dimensional (2D) QLA scattering simulations in the x-z plane are performed for an electromagnetic pulse interacting with a conical dielectric obstacle for the 8-16 qubit model.
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المؤلفون: G.M. Wallace, S.G. Baek, P.T. Bonoli, I.C. Faust, B.L. LaBombard, Y. Lin, R.T. Mumgaard, R.R. Parker, S. Shiraiwa, R. Vieira, D.G. Whyte, S.J. Wukitch
مصطلحات موضوعية: Physics, RF current drive, RF heating, wave absorption, wave coupling, wave interaction wave propagation, waveguides
الوصف: Launching radio frequency (RF) waves from the high field side (HFS) of a tokamak offers significant advantages over low field side (LFS) launch with respect to both wave physics and plasma material interactions (PMI). For lower hybrid (LH) waves, the higher magnetic field opens the window between wave accessibility and the condition for strong electron Landau damping, allowing LH waves from the HFS to penetrate into the core of a burning plasma, while waves launched from the LFS are restricted to the periphery of the plasma. The lower of waves absorbed at higher yields a higher current drive efficiency as well. In the ion cyclotron range of frequencies (ICRF), HFS launch allows for direct access to the mode conversion layer where mode converted waves absorb strongly on thermal electrons and ions, thus avoiding the generation of energetic minority ion tails. The absence of turbulent heat and particle fluxes on the HFS, particularly in double null configuration, makes it the ideal location to minimize PMI damage to the antenna structure. The quiescent SOL also eliminates the need to couple LH waves across a long distance to the separatrix, as the antenna can be located close to plasma without risking damage to the structure. Improved impurity screening on the HFS will help eliminate the long-standing issues of high Z impurity accumulation with ICRF.
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المؤلفون: S. Shiraiwa, J, C. Wright, J. P. Lee, P. Bonoli
مصطلحات موضوعية: Physics, Alcator C-Mod, ICR heating, radio frequency, scrapeoff layer, wave coupling, wave propagation
الوصف: This paper presents a novel approach to incorporating an arbitrarily shaped edge scrape-off-layer (SOL) plasma and an ion cyclotron range of frequency (ICRF) antenna structure into existing core ICRF wave simulation models. We partition the entire computation domain into two sub-domains: a core and an edge region. Simulations in each domain are performed separately with appropriate numerical solvers. For the core, the TORIC ICRF solver [M. Brambilla, Plasma Phys. Contrl. Fusion 41, 1 (1999)] was modified to impose an essential (Dirichlet) boundary condition at its interface with the edge domain. In the edge, a finite element method (FEM) is used to solve a cold collisional plasma model. The domains are then joined together using the continuity boundary condition for the tangential electric and magnetic fields at their interfaces (Hybrid Integration of SOL to TORIC: HIS-TORIC). The model developed here was tested using an ICRH H minority heating scenario on the Alcator C-Mod tokamak [I. Hutchinson et. al., Phys. Plasmas 1, 1511 (1994)]. The simulated pattern of core wave propagation agrees well with a standard TORIC simulation. This approach opens the possibility of using a realistic diverted SOL plasma and a complicated 3D RF antenna together with a rigorous hot core plasma model, while requiring only minimal modification to existing RF codes.
