The ECE imaging ͑ECEI͒ diagnostic tested on the TEXTOR tokamak revealed the sawtooth reconnection physics in unprecedented detail, including the first observation of high-field-side crash and collective heat transport ͓H. K. Park, N. C. Luhmann, Jr., A. J. H. Donné et al., Phys. Rev. Lett. 96, 195003 ͑2006͔͒. An improved ECEI system capable of visualizing both high-and low-field sides simultaneously with considerably better spatial coverage has been developed for the KSTAR tokamak in order to capture the full picture of core MHD dynamics. Direct 2D imaging of other MHD phenomena such as tearing modes, edge localized modes, and even Alfvén eigenmodes is expected to be feasible. Use of ECE images of the optically thin edge region to recover 2D electron density changes during L/H mode transitions is also envisioned, providing powerful information about the underlying physics. The influence of density fluctuations on optically thin ECE is discussed.
Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Tobias, B. J., Domier, C. W., Liang, T., Kong, X., Yu, L., Yun, G. S., ... Luhmann, N. C. (2010). Commissioning of electron cyclotron emission imaging instrument on the DIII-D tokamak and first data. Review of Scientific Instruments, 81(10), 10D928-1/4. DOI: 10.1063/1.3460456 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
The recently theoretical and experimental researches related to PT -symmetric system have attracted unprecedented attention because of various novel features and potentials in extending canonical quantum mechanics. However, as the counterpart of PT -symmetry, there are only a few researches on anti-PT -symmetry. Here, we propose an algorithm for simulating the universal anti-PT -symmetric system with quantum circuit. Utilizing the protocols, an oscillation of information flow is observed for the first time in our Nuclear Magnetic Resonance quantum simulator. We will show that information will recover from the environment completely when the anti-PT -symmetry is broken, whereas no information can be retrieved in the symmetry-unbroken phase. Our work opens the gate for practical quantum simulation and experimental investigation of universal anti-PT -symmetric system in quantum computer. Traditional quantum mechanics requires HermitianHamiltonians to describe closed physical systems, while the dynamic evolution of open systems is typically described by non-Hermitian Hamiltonians [1,2]. The nonhermitian Hamiltonian of open systems has attracted extensive attention and research because of the discovery by Bender and Boettcher in 1998 [3]. It was found that Hamiltonians satisfying parity P (spatial reflection) and T (time reversal) symmetry instead of hermiticity can still have real energy spectra and orthogonal eigenstates in the symmetry-unbroken phase, in which the eigenfunction of system Hamiltonian is at the same time an eigenfunction of the PT operator [4,5]. When the Hamiltonian parameters cross the exceptional point, PT -symmetry will be broken and lead to a symmetrybreaking transition [6][7][8]. This work has inspired numerous theoretical and experimental studies [9-15] of the non-hermitian systems, including demonstrating novel properties of open systems [16,17] and extending fundamental quantum mechanics [20,21]. However, there are limited investigations on another important counterpart anti-PT -symmetry, which means the system Hamiltonian is anti-commutative with the joint PT operator {H, PT } = 0. Some relevant experimental demonstrations have been realized in atoms [29][30][31], optical [32][33][34][35][36][37], electrical circuit resonators [38] and diffusive systems [39]. Quantum processes such as symmetry breaking transition, observation of exceptional point and simulation of anti-PT -symmetric Lorentz dynamics have been presented in these experiments [29,33,37,38], whereas the novel characteristics of entanglement [17][18][19] and information flow [22][23][24] in the anti-PT -symmetric system, which would present various phenomena different from Hermitian quantum mechanics and reveal the relationship between system and environment, have not been fully thorough investigated in the experiment.In this work, we propose an algorithm for the simulation of universal anti-PT -symmetric evolution with quantum circuit model and report the first experimental observation of information flow oscillation in anti-PT...
We present and experimentally realize a quantum algorithm for efficiently solving the following problem: given an N × N matrix M, an N -dimensional vector b, and an initial vector x(0), obtain a target vector x(t) as a function of time t according to the constraint dx(t)/dt = Mx(t) + b. We show that our algorithm exhibits an exponential speedup over its classical counterpart in certain circumstances. In addition, we demonstrate our quantum algorithm for a 4 × 4 linear differential equation using a 4-qubit nuclear magnetic resonance quantum information processor. Our algorithm provides a key technique for solving many important problems which rely on the solutions to linear differential equations. PACS numbers:Introduction. -Linear differential equations (LDEs) are an important framework with which to describe the dynamics of a plethora of physical models, involving classical as well as quantum systems. They are playing key roles in many applications, e.g., predicting climate change and calculating fusion energy. In fact, many of the main applications of supercomputers are in the form of large systems of differential equations [1]. Generally, solving an LDE is a hard problem for a classical high-performance computer, in particular when the size of the configuration space is large, as for example in quantum systems or fluid dynamics.A possible way to overcome the above difficulty is to utilize quantum computing. Quantum information processing is one of the most fruitful fields of research in physics nowadays. Besides the famous Shor's factoring algorithm [2, 3] and Grover's search algorithm [4] , a quantum computer is also capable of solving linear systems of equations [5,6] exponentially faster than any classical computers. In recent years, first steps towards solving linear equations have been demonstrated in optics [7,8], nuclear magnetic resonance (NMR) [9,10], and superconducting circuits [11]. However, extending the algorithm to differential equations is not straightforward. Although some quantum algorithms have been proposed [12][13][14], they are not easily implemented using state-ofthe-art techniques due to the lack of quantum circuits. Therefore, it is timely to design an implementable quantum algorithm and carry out first experimental demonstrations for solving LDEs in controllable quantum platforms.Here, we present a quantum algorithm for solving LDEs only comprising of universal set of quantum gates. The precision of our algorithm can be boosted exponentially by adding the number of ancilla qubits. We further demonstrate it in a 4-qubit NMR system, which is a quantum platform with a
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