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arXiv 2018年

作者： Zhu, Huangjun Hayashi, Masahito Department of Physics and Center for Field Theory and Particle Physics Fudan University Shanghai200433 China State Key Laboratory of Surface Physics Fudan University Shanghai200433 China Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China Institute for Theoretical Physics University of Cologne Cologne50937 Germany Graduate School of Mathematics Nagoya University Nagoya464-8602 Japan Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 Singapore117542 Singapore

Bipartite and multipartite entangled states are of central interest in quantum information processing and foundational studies. Efficient verification of these states, especially in the adversarial scenario, is a key to various applications, such as blind measurement-based quantum computation and quantum networks. Here we offer a general recipe to constructing efficient verification protocols for the adversarial scenario from protocols devised for the nonadversarial scenario. With this recipe, arbitrary pure states can be verified in the adversarial scenario with almost the same efficiency as in the nonadversarial scenario. In addition, we propose a simple protocol for verifying hypergraph states which requires only two distinct Pauli measurements for each party, yet its efficiency is comparable to the best protocol based on entangling measurements. For a given state, the overhead is bounded by the chromatic number and degree of the underlying hypergraph. Our protocol is dramatically more efficient than all known candidates based on local measurements, including tomography and direct fidelity estimation. It enables the verification of hypergraph states and genuine multipartite entanglement of thousands of qubits even in the adversarial scenario. Copyright © 2018, The Authors. All rights reserved.

关键词： quantum entanglement

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quantum annealing for prime factorization

arXiv

引用

arXiv 2018年

作者： Jiang, Shuxian Britt, Keith A. McCaskey, Alexander J. Humble, Travis S. Kais, Sabre Department of Computer Science Purdue University West LafayetteIN47906 United States Quantum Computing Institute Oak Ridge National Laboratory Oak RidgeTN37831 United States Department of Chemistry Physics and Birck Nanotechnology Center Purdue University West LafayetteIN47906 United States

We have developed a framework to convert an arbitrary integer factorization problem to an executable Ising model by first writing it as an optimization function and then transforming the k-bit coupling (k ≥ 3) terms to quadratic terms using ancillary variables. Our resource-efficient method uses O(log2(N)) binary variables (qubits) for finding the factors of an integer N. We present how to factorize 15, 143, 59989, and 376289 using 4, 12, 59, and 94 logical qubits, respectively. This method was tested using the D-Wave 2000Q for finding an embedding and determining the prime factors for a given composite number. The method is general and could be used to factor larger integers as the number of available qubits increases. Copyright © 2018, The Authors. All rights reserved.

关键词： Ising model

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Experimental Low-Latency Device-Independent quantum Randomness

arXiv

引用

arXiv 2018年

作者： Zhang, Yanbao Shalm, Lynden K. Bienfang, Joshua C. Stevens, Martin J. Mazurek, Michael D. Nam, Sae Woo Abellán, Carlos Amaya, Waldimar Mitchell, Morgan W. Fu, Honghao Miller, Carl A. Mink, Alan Knill, Emanuel NTT Basic Research Laboratories NTT Research Center for Theoretical Quantum Physics NTT Corporation 3-1 Morinosato-Wakamiya Atsugi Kanagawa243-0198 Japan National Institute of Standards and Technology BoulderCO80305 United States National Institute of Standards and Technology GaithersburgMD20899 United States 08860 Spain ICREA-Institució Catalana de Recerca i Estudis Avançats Barcelona08010 Spain Department of Computer Science Institute for Advanced Computer Studies Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Theiss Research La JollaCA92037 United States Center for Theory of Quantum Matter University of Colorado BoulderCO80309 United States

Applications of randomness such as private key generation and public randomness beacons require small blocks of certified random bits on demand. Device-independent quantum random number generators can produce such random bits, but existing quantum-proof protocols and loophole-free implementations suffer from high latency, requiring many hours to produce any random bits. We demonstrate device-independent quantum randomness generation from a loophole-free Bell test with a more efficient quantum-proof protocol, obtaining multiple blocks of 512 random bits with an average experiment time of less than 5 min per block and with a certified error bounded by 2−64 ≈ 5.42 × 10−20. Copyright © 2018, The Authors. All rights reserved.

关键词： Random processes

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Goethals-Seidel difference families with symmetric or skew base blocks

arXiv

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arXiv 2018年

作者： Đoković, Dragomir Ž. Kotsireas, Ilias S. University of Waterloo Department of Pure Mathematics Institute for Quantum Computing WaterlooOntarioN2L 3G1 Canada Wilfrid Laurier University Department of Physics & Computer Science WaterlooOntarioN2L 3C5 Canada

We single out a class of difference families which is widely used in some constructions of Hadamard matrices and which we call Goethals-Seidel (GS) difference families. They consist of four subsets (base blocks) of a finite abelian group of order v, which can be used to construct Hadamard matrices via the well-known Goethals-Seidel array. We consider the special class of these families in cyclic groups, where each base block is either symmetric or skew. We omit the well-known case where all four blocks are symmetric. By extending previous computations by several authors, we complete the classification of GS-difference families of this type for odd v 05B10, 05B2005B10, 05B20 Copyright © 2018, The Authors. All rights reserved.

关键词： Hadamard matrices

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Extended nonlocal games from quantum-classical games

arXiv

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arXiv 2017年

作者： Russo, Vincent Watrous, John Institute for Quantum Computing School of Computer Science University of Waterloo Canada Canadian Institute for Advanced Research Toronto Canada

Several variants of nonlocal games have been considered in the study of quantum entanglement and nonlocality. This paper concerns two of these variants, called quantum-classical games and extended nonlocal games. We give a construction of an extended nonlocal game from any quantum-classical game that allows one to translate certain facts concerning quantumclassical games to extended nonlocal games. In particular, based on work of Regev and Vidick, we conclude that there exist extended nonlocal games for which no finite-dimensional entangled strategy can be optimal. While this conclusion is a direct consequence of recent work of Slofstra, who proved a stronger, analogous result for ordinary (non-extended) nonlocal games, the proof based on our construction is considerably simpler, and the construction itself might potentially have other applications in the study of entanglement and nonlocality. Copyright © 2017, The Authors. All rights reserved.

关键词： quantum entanglement

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Field‐Effect Transistors: Low‐Symmetry PdSe2 for High Performance Thermoelectric Applications (Adv. Funct. Mater. 52/2020)

引用

Advanced Functional Materials 2020年第52期30卷 2070347-2070347页

作者： Yunshan Zhao Peng Yu Gang Zhang Minglei Sun Dongzhi Chi Kedar Hippalgaonkar John T. L. Thong Jing Wu NNU‐SULI Thermal Energy Research Center (NSTER) & Center for Quantum Transport and Thermal Energy Science (CQTES) School of Physics and Technology Nanjing Normal University Nanjing 210023 China Institute of Materials Research and Engineering A*STAR (Agency for Science Technology and Research) 2 Fusionopolis Way Innovis #08‐03 Singapore 138634 Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore 117583 Singapore School of Materials Science and Engineering State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat‐Sen University Guangzhou 510275 P. R. China Institute of High Performance Computing Singapore 138632 Singapore Department of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 Singapore

In article number 2004896, John T. L. Thong, Jing Wu, and co‐workers investigate thermoelectric transport in novel 2D palladium diselenide (PdSe2) with a low‐symmetry pentagonal lattice. Due to its sensitive dependence on the interlayer coupling originating from the special lattice structure, the thermoelectric performance can be largely enhanced. The high band convergence and quantum confinement through thickness engineering advance and broaden the applications of thermoelectric such as in soft robotics, health monitoring, and human‐machine interfaces.

关键词： 2D field‐effect transistors palladium diselenide pentagonal crystals thermoelectric devices

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quantum Probability Estimation for Randomness with quantum Side Information

arXiv

引用

arXiv 2018年

作者： Knill, Emanuel Zhang, Yanbao Fu, Honghao National Institute of Standards and Technology BoulderCO80305 United States Center for Theory of Quantum Matter University of Colorado BoulderCO80309 United States NTT Basic Research Laboratories NTT Corporation 3-1 Morinosato-Wakamiya Kanagawa Atsugi243-0198 Japan NTT Research Center for Theoretical Quantum Physics NTT Corporation 3-1 Morinosato-Wakamiya Kanagawa Atsugi243-0198 Japan Joint Institute for Quantum Information and Computer Science University of Maryland College ParkMD20740 United States

We develop a quantum version of the probability estimation framework [arXiv:1709.06159] for randomness generation with quantum side information. We show that most of the properties of probability estimation hold for quantum probability estimation (QPE). This includes asymptotic optimality at constant error and randomness expansion with logarithmic input entropy. QPE is implemented by constructing model-dependent quantum estimation factors (QEFs), which yield statistical confidence upper bounds on data-conditional normalized Rényi powers. This leads to conditional min-entropy estimates for randomness generation. The bounds are valid for relevant models of sequences of experimental trials without requiring independent and identical or stationary behavior. QEFs may be adapted to changing conditions during the sequence and trials can be stopped any time, such as when the results so far are satisfactory. QEFs can be constructed from entropy estimators to improve the bounds for conditional min-entropy of classical-quantum states from the entropy accumulation framework [Dupuis, Fawzi and Renner, arXiv:1607.01796]. QEFs are applicable to a larger class of models, including models permitting experimental devices with super-quantum but non-signaling behaviors and semi-device dependent models. The improved bounds are relevant for finite data or error bounds of the form e−κs, where s is the number of random bits produced. We give a general construction of entropy estimators based on maximum probability estimators, which exist for many configurations. For the class of (k, 2, 2) Bell-test configurations we provide schemas for directly optimizing QEFs to overcome the limitations of entropy-estimator-based constructions. We obtain and apply QEFs for examples involving the (2, 2, 2) Bell-test configuration to demonstrate substantial improvements in finite-data efficiency. Copyright © 2018, The Authors. All rights reserved.

关键词： Error analysis

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Accelerated quantum walk, two-particle entanglement generation and localization

引用

Journal of Physics Communications 2019年第5期3卷 055008-055008页

作者： Singh, Shivani Balu, Radhakrishnan Laflamme, Raymond Chandrashekar, C.M. The Institute of Mathematical Sciences C. I. T Campus Taramani Chennai 600113 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai 400094 India U.S. Army Research Laboratory Adelphi 20783 MD United States Computer Science and Electrical Engineering University of Maryland Baltimore County 1000 Hilltop Circle Baltimore 21250 MD United States Institute for Quantum Computing Department of Physics and Astronomy University of Waterloo Waterloo N2L 3G1 ON Canada Perimeter Institute for Theoretical Physics Waterloo N2L 2Y5 ON Canada

We present a scheme to describe the dynamics of accelerating discrete-time quantum walk for one-and two-particle in position space. We show the effect of acceleration in enhancing the entanglement between the particle and position space in one-particle quantum walk and in generation of entanglement between the two unentangled particle in two-particle quantum walk. By introducing the disorder in the form of phase operator we study the transition from localization to delocalization as a function of acceleration. These inter-winding connection between acceleration, entanglement generation and localization along with well established connection of quantum walks with Dirac equation can be used to probe further in the direction of understanding the connection between acceleration, mass and entanglement in relativistic quantum mechanics and quantum field theory. Expansion of operational tools for quantum simulations and for modelling quantum dynamics of accelerated particle using quantum walks is an other direction where these results can play an important role. © 2019 The Author(s). Published by IOP Publishing Ltd.

关键词： Acceleration Entanglement Localization quantum walk

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Intrinsic 1T̕ phase induced in atomically thin 2H-MoTe2 by a single terahertz pulse

arXiv

引用

arXiv 2019年

作者： Shi, Jiaojian Bie, Ya-Qing Zong, Alfred Fang, Shiang Chen, Wei Han, Jinchi Cao, Zhaolong Zhang, Yong Taniguchi, Takashi Watanabe, Kenji Bulović, Vladimir Kaxiras, Efthimios Baldini, Edoardo Jarillo-Herrero, Pablo Nelson, Keith A. Department of Chemistry Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States State Key Lab of Optoelectronic Materials and Technologies Guangdong Province Key Laboratory of Display Material and Technology School of Electronics and Information Technology Sun Yat-sen University Guangzhou510275 China Department of Chemistry University of California BerkeleyCA94720 United States Department of Physics Harvard University CambridgeMA02138 United States Department of Physics and Astronomy Center for Materials Theory Rutgers University PiscatawayNJ08854 United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Center for Materials Science & Engineering Massachusetts Institute of Technology CambridgeMA02139 United States International Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Functional Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Physics Center for Complex Quantum System The University of Texas at Austin AustinTX78712 United States

Polymorphic transitions in layered transition metal dichalcogenides provide an excellent platform for discovering exotic phenomena associated with metastable states, ranging from topological phase transitions1 to enhanced superconductivity2. In particular, the transition from 2H to 1T0-MoTe2, which was thought to be induced by high-energy photon irradiation3–5 among many other means6–9, has been intensely studied for its technological relevance in nanoscale transistors3. Despite the remarkable electrical performance arising from this 2H-to-1T0 transition, it remains controversial whether a crystalline 1T0 phase is produced because optical signatures of this putative transition are found to be associated with the formation of elemental Te clusters instead10,11. Here, we demonstrate the creation of an intrinsic 1T0 lattice after irradiating a mono- or few-layer 2H-MoTe2 with a single field-enhanced terahertz pulse, whose low photon energy limits possible structural damage by optical pulses. To visualize the temporal evolution of this irreversible transition, we further develop a single-shot terahertz pump-second harmonic probe technique, and we find that the transition out of the 2H phase occurs within 10 ns after photoexcitation. Our results not only resolve the long-standing debate over the light-induced polymorphic transition in MoTe2, they also highlight the unique capability of strong-field terahertz pulses in manipulating the structure of quantum materials. Copyright © 2019, The Authors. All rights reserved.

关键词： Transition metals

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Sequential scheme for locally discriminating bipartite unitary operations without inverses

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Physical Review A 2017年第2期96卷 022303-022303页

作者： Lvzhou Li Institute of Computer Science Theory School of Data and Computer Science Sun Yat-sen University Guangzhou 510006 China and Ministry of Education Key Laboratory of Machine Intelligence and Advanced Computing (Sun Yat-sen University) Guangzhou China

Local distinguishability of bipartite unitary operations has recently received much attention. A nontrivial and interesting question concerning this subject is whether there is a sequential scheme for locally discriminating between two bipartite unitary operations, because a sequential scheme usually represents the most economic strategy for discrimination. An affirmative answer to this question was given in the literature, however with two limitations: (i) the unitary operations to be discriminated were limited to act on d⊗d, i.e., a two-qudit system, and (ii) the inverses of the unitary operations were assumed to be accessible, although this assumption may be unrealizable in experiment. In this paper, we improve the result by removing the two limitations. Specifically, we show that any two bipartite unitary operations acting on dA⊗dB can be locally discriminated by a sequential scheme, without using the inverses of the unitary operations. Therefore, this paper enhances the applicability and feasibility of the sequential scheme for locally discriminating unitary operations.

关键词： quantum channels quantum gates

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