检索结果-内蒙古大学图书馆

Distinguishing unitary gates on the IBM quantum processor

学校读者我要写书评

暂无评论

science China(Information sciences) 2019年第7期62卷 210-216页

作者： Shusen LIU Yinan LI Runyao DUAN School of Data and Computer Science Sun Yat-sen University Centre for Quantum Software and Information Faculty of Engineering and Information TechnologyUniversity of Technology Sydney Centrum Wiskunde & Informatica and Research Center for Quantum Software Institute for Quantum Computing

An unknown unitary gate, which is secretly chosen from several known ones, can always be distinguished perfectly. In this paper, we implement such a task on IBM's quantum processor. More precisely,we experimentally demonstrate the discrimination of two qubit unitary gates, the identity gate and the 2/3π-phase shift gate, using two discrimination schemes — the parallel scheme and the sequential scheme. We program these two schemes on the ibmqx4, a 5-qubit superconducting quantum processor via IBM cloud,with the help of the QSI modules. We report that both discrimination schemes achieve success probabilities at least 85%.

关键词： quantum experiment IBM quantum computer software-aided quantum experiment sequential schemes for unitary discrimination parallel schemes for unitary discrimination

Exact distributed quantum algorithm for generalized Simon’s problem

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Li, Hao Qiu, Daowen Luo, Le Mateus, Paulo Institute of Quantum Computing and Computer Theory School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China The Guangdong Key Laboratory of Information Security Technology Sun Yat-sen University 510006 China QUDOOR Technologies Inc. Zhuhai China School of Physics and Astronomy Sun Yat-sen University Zhuhai519082 China Instituto de Telecomunicações Departamento de Matemática Instituto Superior Técnico Av. Rovisco Pais Lisbon1049-001 Portugal

Simon’s problem is one of the most important problems demonstrating the power of quantum algorithms, as it greatly inspired the proposal of Shor’s algorithm. The generalized Simon’s problem is a natural extension of Simon’s problem, and also a special hidden subgroup problem: Given a function f : {0, 1}n → {0, 1}m, with the property that for any x, y ∈ {0, 1}n, there is some unknown hidden subgroup S ≤ 2n such that f(x) = f(y) iff x ⊕ y ∈ S, where |S| = 2k for some 0 ≤ k ≤ n (m ≥ n − k). The goal of generalized Simon’s problem is to find the hidden subgroup S. In this paper, we present two key contributions. Firstly, we characterize the structure of the generalized Simon’s problem in distributed scenario and introduce a corresponding distributed quantum algorithm. Secondly, we refine the algorithm to ensure exactness due to the application of quantum amplitude amplification technique. Our algorithm offers exponential acceleration compared to the distributed classical algorithm. When contrasted with the centralized quantum algorithm for the generalized Simon’s problem, our algorithm’s oracle requires fewer qubits, thus making it easier to be physically implemented. Particularly, the exact distributed quantum algorithm we develop for the generalized Simon’s problem outperforms the best previously proposed distributed quantum algorithm for Simon’s problem in terms of generalizability and exactness. Copyright © 2023, The Authors. All rights reserved.

关键词： Qubits

Benchmarking quantum Optimization for the Maximum-Cut Problem on a Superconducting quantum computer

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Dupont, Maxime Sundar, Bhuvanesh Evert, Bram Bernal Neira, David E. Peng, Zedong Jeffrey, Stephen Hodson, Mark J. Rigetti Computing 775 Heinz Avenue BerkeleyCA94710 United States Davidson School of Chemical Engineering Purdue University West LafayetteIN47907 United States USRA Research Institute for Advanced Computer Science Mountain ViewCA94043 United States Quantum AI Laboratory NASA Ames Research Center Moffett Field CA94035 United States

Achieving high-quality solutions faster than classical solvers on computationally hard problems is a challenge for quantum optimization to deliver utility. Using a superconducting quantum computer, we experimentally investigate the performance of a hybrid quantum-classical algorithm inspired by semidefinite programming approaches for solving the maximum-cut problem on 3-regular graphs up to several thousand variables. We leverage the structure of the input problems to address sizes beyond what current quantum machines can naively handle. We attain an average approximation ratio of 99% over a random ensemble of thousands of problem instances. We benchmark the quantum solver against similarly high-performing classical heuristics, including the Gurobi optimizer, simulated annealing, and the Burer-Monteiro algorithm. A run-time analysis shows that the quantum solver on large-scale problems is competitive against Gurobi but short of others on a projected 100-qubit quantum computer. We explore multiple leads to close the gap and discuss prospects for a practical quantum speedup. Copyright © 2024, The Authors. All rights reserved.

关键词： Simulated annealing

Preparing a commercial quantum key distribution system for certification against implementation loopholes

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Makarov, Vadim Abrikosov, Alexey Chaiwongkhot, Poompong Fedorov, Aleksey K. Huang, Anqi Kiktenko, Evgeny Petrov, Mikhail Ponosova, Anastasiya Ruzhitskaya, Daria Tayduganov, Andrey Trefilov, Daniil Zaitsev, Konstantin Russian Quantum Center Skolkovo Moscow121205 Russia Vigo Quantum Communication Center University of Vigo VigoE-36310 Spain NTI Center for Quantum Communications National University of Science and Technology MISiS Moscow119049 Russia Department of Physics Faculty of Science Mahidol University Bangkok10400 Thailand Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Bangkok10110 Thailand QRate Skolkovo Moscow143026 Russia Institute for Quantum Information State Key Laboratory of High Performance Computing College of Computer Science and Technology National University of Defense Technology Changsha410073 China Steklov Mathematical Institute Russian Academy of Sciences Moscow119991 Russia atlanTTic Research Center University of Vigo VigoE-36310 Spain School of Telecommunication Engineering Department of Signal Theory and Communications University of Vigo VigoE-36310 Spain National Research University Higher School of Economics Moscow101000 Russia

A commercial quantum key distribution (QKD) system needs to be formally certified to enable its wide deployment. The certification should include the system’s robustness against known implementation loopholes and attacks that exploit them. Here we ready a fiber-optic QKD system for this procedure. The system has a prepare-and-measure scheme with decoy-state BB84 protocol, polarisation encoding, qubit source rate of 312.5 MHz, and is manufactured by QRate. We detail its hardware and post-processing. We analyse the hardware for known implementation loopholes, search for possible new loopholes, and discuss countermeasures. We then amend the system design to address the highest-risk loopholes identified. We also work out technical requirements on the certification lab and outline its possible structure. Copyright © 2023, The Authors. All rights reserved.

关键词： quantum cryptography

Decoherence on staggered quantum walks

学校读者我要写书评

暂无评论

Physical Review A 2022年第3期105卷 032452-032452页

作者： Raqueline A. M. Santos Franklin de L. Marquezino Center for Quantum Computer Science Faculty of Computing University of Latvia Raina bulvaris 19 Riga LV-1586 Latvia Systems Engineering and Computer Science Alberto Luiz Coimbra Institute for Graduate Studies and Research in Engineering Federal University of Rio de Janeiro Avenida Horacio Macedo 2030 H319 Rio de Janeiro 21941-972 Brazil Multidisciplinary Laboratory for Research in Computer Science Federal University of Rio de Janeiro Rodovia Washington Luiz 19593 Duque de Caxias 25240-005 Brazil

The decoherence phenomenon has been widely studied in different types of quantum walks. In this work we show how to model decoherence inspired by percolation on staggered quantum walks. Two models of unitary noise are described: breaking polygons and breaking vertices. The evolution operators subject to these noises are obtained, and the equivalence to the coined quantum walk model is presented. Further, we numerically analyze the effect of these decoherence models on the two-dimensional grid of 4-cliques. We examine how these perturbations affect the quantum walk based search algorithm in this graph and how expanding the tessellation intersection can make it more robust against decoherence.

关键词： Network searches quantum algorithms quantum computation quantum information processing quantum walks

Neural-Network Decoders for Measurement Induced Phase Transitions

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Dehghani, Hossein Lavasani, Ali Hafezi, Mohammad Gullans, Michael J. Joint Quantum Institute NIST University of Maryland College ParkMD20742 United States Joint Center for Quantum Information and Computer Science NIST University of Maryland College ParkMD20742 United States Condensed Matter Theory Center University of Maryland College ParkMD20742 United States

Open quantum systems have been shown to host a plethora of exotic dynamical phases. Measurement-induced entanglement phase transitions in monitored quantum systems are a striking example of this phenomena. However, naive realizations of such phase transitions requires an exponential number of repetitions of the experiment which is practically unfeasible on large systems. Recently, it has been proposed that these phase transitions can be probed locally via entangling reference qubits and studying their purification dynamics. In this work, we leverage modern machine learning tools to devise a neural network decoder to determine the state of the reference qubits conditioned on the measurement outcomes. We show that the entanglement phase transition manifests itself as a stark change in the learnability of the decoder function. We study the complexity and scalability of this approach in both Clifford and Haar random circuits and discuss how it can be utilized to detect entanglement phase transitions in generic experiments. Copyright © 2022, The Authors. All rights reserved.

关键词： Qubits

qSWIFT: High-order randomized compiler for Hamiltonian simulation

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Nakaji, Kouhei Bagherimehrab, Mohsen Aspuru-Guzik, Alán Chemical Physics Theory Group Department of Chemistry University of Toronto TorontoON Canada 1-1-1 Umezono Ibaraki Tsukuba305-8568 Japan Quantum Computing Center Keio University 3-14-1 Hiyoshi Kohoku-ku Kanagawa Yokohama223-8522 Japan Department of Computer Science University of Toronto TorontoON Canada Vector Institute for Artificial Intelligence TorontoON Canada Department of Chemical Engineering & Applied Chemistry University of Toronto TorontoON Canada Department of Materials Science & Engineering University of Toronto TorontoON Canada Canadian Institute for Advanced Research TorontoON Canada

Hamiltonian simulation is known to be one of the fundamental building blocks of a variety of quantum algorithms such as its most immediate application, that of simulating many-body systems to extract their physical properties. In this work, we present qSWIFT, a high-order randomized algorithm for Hamiltonian simulation. In qSWIFT, the required number of gates for a given precision is independent of the number of terms in Hamiltonian, while the systematic error is exponentially reduced with regards to the order parameter. In this respect, our qSWIFT is a higher-order counterpart of the previously proposed quantum stochastic drift protocol (qDRIFT), in which the number of gates scales linearly with the inverse of the precision required. We construct the qSWIFT channel and establish a rigorous bound for the systematic error quantified by the diamond norm. qSWIFT provides an algorithm to estimate given physical quantities using a system with one ancilla qubit, which is as simple as other product-formula-based approaches such as regular Trotter-Suzuki decompositions and qDRIFT. Our numerical experiment reveals that the required number of gates in qSWIFT is significantly reduced compared to qDRIFT. Particularly, the advantage is significant for problems where high precision is required;for example, to achieve a systematic relative propagation error of 10−6, the required number of gates in third-order qSWIFT is 1000 times smaller than that of qDRIFT. © 2023, CC BY.

关键词： Hamiltonians

Self-congruent point in critical matrix product states: An effective field theory for finite-entanglement scaling

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Schneider, Jan T. Ueda, Atsushi Liu, Yifan Läuchli, Andreas M. Oshikawa, Masaki Tagliacozzo, Luca Institute of Fundamental Physics IFF-CSIC Calle Serrano 113b Madrid28006 Spain Department of Physics and Astronomy University of Ghent Ghent9000 Belgium Institute for Solid State Physics University of Tokyo Kashiwa277-8581 Japan Laboratory for Theoretical and Computational Physics PSI Center for Scientific Computing Theory and Data Villigen5232 Switzerland Lausanne1015 Switzerland University of Tokyo Kashiwa277-8583 Japan Trans-scale Quantum Science Institute University of Tokyo Bunkyo-ku Tokyo113-0033 Japan

We set up an effective field theory formulation for the renormalization flow of matrix product states (MPS) with finite bond dimension, focusing on systems exhibiting finite-entanglement scaling close to a conformally invariant critical fixed point. We show that the finite MPS bond dimension χ is equivalent to introducing a perturbation by a relevant operator to the fixed-point Hamiltonian. The fingerprint of this mechanism is encoded in the χ-independent universal transfer matrix’s gap ratios, which are distinct from those predicted by the unperturbed Conformal Field theory (CFT). This phenomenon defines a renormalization group self-congruent point, where the relevant coupling constant ceases to flow due to a balance of two effects;When increasing χ, the infrared scale, set by the correlation length ξ(χ), increases, while the strength of the perturbation at the lattice scale decreases. The presence of a self-congruent point does not alter the validity of the finite-entanglement scaling hypothesis, since the self-congruent point is located at a finite distance from the critical fixed point, well inside the scaling regime of the CFT. We corroborate this framework with numerical evidence from the exact solution of the Ising model and density matrix renormalization group (DMRG) simulations of an effective lattice model. Copyright © 2024, The Authors. All rights reserved.

关键词： Hamiltonians

A Review of Barren Plateaus in Variational quantum computing

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Larocca, Martín Thanasilp, Supanut Wang, Samson Sharma, Kunal Biamonte, Jacob Coles, Patrick J. Cincio, Lukasz McClean, Jarrod R. Holmes, Zoë Cerezo, M. Theoretical Division Los Alamos National Laboratory Los AlamosNM87545 United States Center for Non-Linear Studies Los Alamos National Laboratory NM87545 United States LausanneCH-1015 Switzerland Chula Intelligent and Complex Systems Department of Physics Faculty of Science Chulalongkorn University Bangkok10330 Thailand Institute for Quantum Information and Matter Caltech PasadenaCA91125 United States IBM Quantum IBM T.J. Watson Research Center Yorktown HeightsNY10598 United States Quantum Artificial Intelligence Laboratory NASA Ames Research Center Moffett Federal Airfield Mountain ViewCA94035 United States Simons Institute for the Theory of Computing University of California BerkeleyCA94720-2190 United States Normal Computing Corporation New YorkNY United States Quantum Science Center Oak RidgeTN37931 United States Google Quantum AI VeniceCA90291 United States Information Sciences Los Alamos National Laboratory NM87545 United States

Variational quantum computing offers a flexible computational paradigm with applications in diverse areas. However, a key obstacle to realizing their potential is the Barren Plateau (BP) phenomenon. When a model exhibits a BP, its parameter optimization landscape becomes exponentially flat and featureless as the problem size increases. Importantly, all the moving pieces of an algorithm—choices of ansatz, initial state, observable, loss function and hardware noise—can lead to BPs when ill-suited. Due to the significant impact of BPs on trainability, researchers have dedicated considerable effort to develop theoretical and heuristic methods to understand and mitigate their effects. As a result, the study of BPs has become a thriving area of research, influencing and cross-fertilizing other fields such as quantum optimal control, tensor networks, and learning theory. This article provides a comprehensive review of the current understanding of the BP phenomenon. Copyright © 2024, The Authors. All rights reserved.

关键词： Heuristic methods