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Annual IEEE Northeast Workshop on Circuits and Systems (NEWCAS)

作者： Fayçal Saffih Amro M. Elshurafa Mohammad Ali Mohammad Nathaniel Nelson-Fitzpatrick Stephane Evoy Physical Science and Engineering King Abdullah University for Science and Technology Thuwal Saudi Arabia Department of Electrical and Computer Engineering ECERF W2-085 University of Alberta Edmonton AB Canada Institute for Quantum Computing University of Waterloo Waterloo ONT Canada

In this paper, nanopillars with heights of 1μm to 5μm and widths of 250nm to 500nm have been fabricated with a near room temperature etching process. The nanopillars were achieved with a continuous deep reactive ion etching technique and utilizing PMMA (polymethylmethacrylate) and Chromium as masking layers. As opposed to the conventional Bosch process, the usage of the unswitched deep reactive ion etching technique resulted in nanopillars with smooth sidewalls with a measured surface roughness of less than 40nm. Moreover, undercut was nonexistent in the nanopillars. The proposed fabrication method achieves etch rates four times faster when compared to the state-of-the-art, leading to higher throughput and more vertical side walls. The fabrication of the nanopillars was carried out keeping the CMOS process in mind to ultimately obtain a CMOS-compatible process. This work serves as an initial step in the ultimate objective of integrating photo-sensors based on these nanopillars seamlessly along with the controlling transistors to build a complete bio-inspired smart CMOS image sensor on the same wafer.

关键词： Etching Fabrication Silicon Nanobioscience CMOS integrated circuits Biomedical imaging Educational institutions

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Faster quantum algorithm for evaluating game trees

Faster quantum algorithm for evaluating game trees

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作者： Reichardt, Ben W. School of Computer Science Institute for Quantum Computing University of Waterloo Canada

ISBN: (纸本)9780898719932

We give an O(√n log n)-query quantum algorithm for evaluating size-n AND-OR formulas. Its rumiing time is poly-logarithinically greater after efficient preprocessing. Unlike previous approaches, the algorithm is based on a quantum walk on a graph that is not a tree. Instead, the algorithm is based on a hybrid of direct-sum span program composition, which generates tree-like graphs, and a novel tensor-product span program composition method, which generates graphs with vertices corresponding to minimal zero-certificates.

关键词： Trees (mathematics)

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Reflections for quantum query algorithms

Reflections for quantum query algorithms

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作者： Reichardt, Ben W. School of Computer Science Institute for Quantum Computing University of Waterloo Canada

ISBN: (纸本)9780898719932

We show that any boolean function can be evaluated optimally by a quantum query algorithm that alteinates a certain fixed, input-independent reflection with a second reflection that coherently queries the input string. Originally introduced for solving the unstructured search problem, this two-reflections structure is therefore a universal feature of quantum algorithms. Our proof goes via the general adversary bound, a semi-definite program (SDP) that lower-bounds the quantum query complexity of a function. By a quantum algorithm for evaluating span programs, this lower bound is known to be tight up to a sub-logarithinic factor. The extra factor comes from converting a continuous-time query algorithm into a discrete-query algorithm. We give a direct and simplified quantum algorithm based on the dual SDP, with a bounded-error query complexity that matches the general adversary bound. Therefore, the general adversary lower bound is tight;it is in fact an SDP for quantum query complexity. This implies that the quantum query complexity of the composition f o (g.-,g) of two boolean functions f and g matches the product of the query complexities of f and g, without a logarithmic factor for error reduction. It efficiently characterizes the quantum query complexity of a read-once formula over any finite gate set. It further shows that span programs are equivalent to quantum query algorithms.

关键词： Boolean functions

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Equation of state for the one-dimensional attractive δ-potential Bose gas in the weak-coupling regime

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Physical Review A 2012年第1期86卷 015602-015602页

作者： Tsubasa Ichikawa Izumi Tsutsui Nobuhiro Yonezawa Research Center for Quantum Computing Interdisciplinary Graduate School of Science and Engineering Kinki University 3-4-1 Kowakae Higashi-Osaka 577-8502 Japan Theory Center Institute of Particle and Nuclear Studies High Energy Accelerator Research Organization (KEK) 1-1 Oho Tsukuba Ibaraki 305-0801 Japan Osaka City University Advanced Mathematical Institute (OCAMI) 3-3-138 Sugimoto Sumiyoshi-ku Osaka 558-8585 Japan

Approximated formulas for real quasimomentum and the associated energy spectrum are presented for one-dimensional Bose gas with weak attractive contact interactions. On the basis of the energy spectrum, we obtain the equation of state in the high-temperature region, which is found to be the van der Waals equation without volume correction.

关键词： BOSE-Einstein gas HIGH temperatures VAN der Waals forces VOLUME (Cubic content) MOMENTUM (Mechanics)

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Number-Theoretic Nature of Communication in quantum Spin Systems

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Physical Review Letters 2012年第5期109卷 050502-050502页

作者： Chris Godsil Stephen Kirkland Simone Severini Jamie Smith Combinatorics & Optimization University of Waterloo N2L 3G1 Waterloo Canada Hamilton Institute National University of Ireland Maynooth County Kildare Ireland Department of Computer Science and Department of Physics & Astronomy University College London WC1E 6BT London United Kingdom Institute for Quantum Computing and Combinatorics & Optimization University of Waterloo N2L 3G1 Waterloo Canada

The last decade has witnessed substantial interest in protocols for transferring information on networks of quantum mechanical objects. A variety of control methods and network topologies have been proposed, on the basis that transfer with perfect fidelity—i.e., deterministic and without information loss—is impossible through unmodulated spin chains with more than a few particles. Solving the original problem formulated by Bose [Phys. Rev. Lett. 91, 207901 (2003)], we determine the exact number of qubits in unmodulated chains (with an XY Hamiltonian) that permit transfer with a fidelity arbitrarily close to 1, a phenomenon called pretty good state transfer. We prove that this happens if and only if the number of nodes is n=p−1, 2p−1, where p is a prime, or n=2m−1. The result highlights the potential of quantum spin system dynamics for reinterpreting questions about the arithmetic structure of integers and, in this case, primality.

关键词： KNOWLEDGE transfer (Communication) quantum theory INFORMATION networks NATURAL numbers ARITHMETIC

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quantum property testing for bounded-degree graphs 1

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Lecture Notes in computer science

作者： Ambainis, Andris Childs, Andrew M. Liu, Yi-Kai Faculty of Computing University of Latvia Latvia Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo Canada Department of Computer Science University of California Berkeley CA United States

ISBN: (数字)9783642229350

ISBN: (纸本)9783642229343

We study quantum algorithms for testing bipartiteness and expansion of bounded-degree graphs. We give quantum algorithms that solve these problems in time Õ(N1/3), beating the Ω(√N) classical lower bound. For testing expansion, we also prove an Ω(N1/4) quantum query lower bound, thus ruling out the possibility of an exponential quantum speedup. Our quantum algorithms follow from a combination of classical property testing techniques due to Goldreich and Ron, derandomization, and the quantum algorithm for element distinctness. The quantum lower bound is obtained by the polynomial method, using novel algebraic techniques and combinatorial analysis to accommodate the graph structure. © 2011 Springer-Verlag.

关键词： Testing

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Authentication of quantum messages

Authentication of quantum messages

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Applications of Lasers for Sensing and Free Space Communications, LSC 2011

作者： Hayden, Patrick Leung, Debbie Mayers, Dominic School of Computer Science McGill University Montreal QC Canada Department of Combinatorics and Optimization Institute for Quantum Computing University of Waterloo Waterloo ON Canada Institute for Quantum Information Caltech Pasadena CA United States

ISBN: (纸本)9781557529145

Message authentication is a cryptographic task that allows the receiver to reject a message that is forged or has been tampered with. A protocol to authenticate quantum messages was proposed by Barnum, Crépeau, Gottesman, Tapp, and Smith [1] and stand-alone security was proved. Here, we are concerned with universal composable security (which requires a protocol to be essentially indistinguishable from the ideal functionality and ensures overall security when the protocol is part of any larger scheme). We show that the protocol in [1] is universal composably secure, and that most of the required key can be reused with universal composable security. © 2011 Optical Society of America.

关键词： Authentication

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No-go theorem for one-way quantum computing on naturally occurring two-level systems

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Physical Review A 2011年第5期83卷 050301(R)-050301(R)页

作者： Jianxin Chen Xie Chen Runyao Duan Zhengfeng Ji Bei Zeng Department of Computer Science and Technology Tsinghua National Laboratory for Information Science and Technology Tsinghua University Beijing China Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts USA Centre for Quantum Computation and Intelligent Systems (QCIS) Faculty of Engineering and Information Technology University of Technology Sydney New South Wales Australia Perimeter Institute for Theoretical Physics Waterloo Ontario Canada State Key Laboratory of Computer Science Institute of Software Chinese Academy of Sciences Beijing China Institute for Quantum Computing and Department of Combinatorics and Optimization University of Waterloo Waterloo Ontario Canada

The ground states of some many-body quantum systems can serve as resource states for the one-way quantum computing model, achieving the full power of quantum computation. Such resource states are found, for example, in spin-52 and spin-32 systems. It is, of course, desirable to have a natural resource state in a spin-12, that is, qubit system. Here, we give a negative answer to this question for frustration-free systems with two-body interactions. In fact, it is shown to be impossible for any genuinely entangled qubit state to be a nondegenerate ground state of any two-body frustration-free Hamiltonian. What is more, we also prove that every spin-12 frustration-free Hamiltonian with two-body interaction always has a ground state that is a product of single- or two-qubit states. In other words, there cannot be any interesting entanglement features in the ground state of such a qubit Hamiltonian.

关键词： quantum computers quantum theory HAMILTONIAN operator HAMILTONIAN systems PHYSICS

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Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

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Physical Review B 2012年第17期85卷 174521-174521页

作者： Fei Yan Jonas Bylander Simon Gustavsson Fumiki Yoshihara Khalil Harrabi David G. Cory Terry P. Orlando Yasunobu Nakamura Jaw-Shen Tsai William D. Oliver Department of Nuclear Science and Engineering Massachusetts Institute of Technology (MIT) Cambridge Massachusetts 02139 USA Research Laboratory of Electronics MIT Cambridge Massachusetts 02139 USA Institute of Physical and Chemical Research (RIKEN) Wako Saitama 351-0198 Japan Institute for Quantum Computing and Department of Chemistry University of Waterloo Ontario Canada N2L 3G1 Perimeter Institute for Theoretical Physics Waterloo Ontario Canada N2J 2W9 Department of Electrical Engineering and Computer Science MIT Cambridge Massachusetts 02139 USA Green Innovation Research Laboratories NEC Corporation Tsukuba Ibaraki 305-8501 Japan MIT Lincoln Laboratory 244 Wood Street Lexington Massachusetts 02420 USA

We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables Fourier-transform noise spectroscopy with access to frequencies up to the achievable repetition rate, a regime relevant to dephasing in ensemble-averaged time-domain measurements such as Ramsey interferometry. Rotating the qubit's quantization axis allows us to measure two types of noise: effective flux noise and effective critical-current or charge noise. For both noise sources, we observe that the very same 1/f-type power laws measured at considerably higher frequencies (0.2−20 MHz) are consistent with the noise in the 0.01−100-Hz range measured here. We find no evidence of temperature dependence of the noises over 65−200 mK, and also no evidence of time-domain correlations between the two noises. These methods and results are pertinent to the dephasing of all superconducting qubits.

关键词： QUBITS PHYSICS experiments SUPERCONDUCTORS FOURIER transform infrared spectroscopy TIME-domain analysis CORRELATION (Statistics) TEMPERATURE effect

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Faster quantum algorithm for evaluating game trees 11

Faster quantum algorithm for evaluating game trees

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Annual ACM-Society for Industrial and Applied Mathmatics Symposium on Discrete Algorithms

作者： Ben W. Reichardt School of Computer Science and Institute for Quantum Computing University of Waterloo

ISBN: (纸本)9780898719932

We give an O(n~(1/2) log n)-query quantum algorithm for evaluating size-n AND-OR formulas. Its running time is poly-logarithmically greater after efficient preprocessing. Unlike previous approaches, the algorithm is based on a quantum walk on a graph that is not a tree. Instead, the algorithm is based on a hybrid of direct-sum span program composition, which generates tree-like graphs, and a novel tensor-product span program composition method, which generates graphs with vertices corresponding to minimal zero-certificates.

关键词： game tree algorithms quanta Runtime formula

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