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Depth-2 QAC circuits cannot simulate quantum parity

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arXiv 2020年

作者： Padé, Daniel Fenner, Stephen Grier, Daniel Thierauf, Thomas IQC Canada Aalen University Germany University of South Carolina United States Computer Science and Engineering Department ColumbiaSC29208 United States Institute for Quantum Computing University of Waterloo WaterlooONN2L3G1 Canada Department of Computer Science and Electrical Engineering Aalen Germany

We show that the quantum parity gate on n > 3 qubits cannot be cleanly simulated by a quantum circuit with two layers of arbitrary C-SIGN gates of any arity and arbitrary 1-qubit unitary gates, regardless of the number of allowed ancilla qubits. This is the best known and first nontrivial separation between the parity gate and circuits of this form. The same bounds also apply to the quantum fanout gate. Our results are incomparable with those of Fang et al. [3], which apply to any constant depth but require a sublinear number of ancilla qubits on the simulating *** Codes 68Q12 (Primary) 68Q15, 68Q17 (Secondary) Copyright © 2020, The Authors. All rights reserved.

关键词： Timing circuits

Load Balancing a Multi-Block Grids-based Application on Heterogeneous Platform

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Load Balancing a Multi-Block Grids-based Application on Hete...

IEEE International Conference on Computational science and Engineering, CSE

作者： Yonggang Che Chuanfu Xu Zhenghua Wang Institute for Quantum Information & State Key Lab. of High Performance Computing College of Computer National University of Defense Technology Changsha China Science and Technology on Parallel and Distributed Processing Lab National University of Defense Technology Changsha China

ISBN: (数字)9781665403986

ISBN: (纸本)9781665403993

This paper presents a load balancing method for a multi-block grids-based CFD (Computational Fluid Dynamics) application on heterogeneous platform. This method includes an asymmetric task scheduling scheme and a load balancing model. The idea is to balance the computing speed between the CPU and the coprocessor by adjusting the workload and the numbers of threads on both sides. Optimal load balance parameters are empirically selected, guided by a performance model. Performance evaluation is conducted on a computer server consists of two Intel Xeon E5-2670 v3 CPUs and two MIC coprocessors (Xeon Phi 5110P and Xeon Phi 7120P) for the simulation of turbulent combustion in a supersonic combustor. The results show that the performance is highly sensitive to the load balance parameters. With the optimal parameters, the heterogeneous computing achieves a maximum speedup of 2.30 × for a 6-block mesh, and a maximum speedup of 2.66 × for a 8-block mesh, over the CPU-only computing.

关键词： Computational modeling Computational fluid dynamics Load management Servers Task analysis Load modeling Coprocessors

Emergence of kinematic space from quantum modular geometric tensor

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arXiv 2021年

作者： Huang, Xing Ma, Chen-Te Institute of Modern Physics Northwest University Xi’an710069 China NSFC-SPTP Peng Huanwu Center for Fundamental Theory Xi’an710127 China Shaanxi Key Laboratory for Theoretical Physics Frontiers Xi’an710069 China Asia Pacific Center for Theoretical Physics Pohang University of Science and Technology Gyeongsangbuk-do Pohang37673 Korea Republic of Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangdong Guangzhou510006 China School of Physics and Telecommunication Engineering South China Normal University Guangdong Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangdong Guangzhou510006 China The Laboratory for Quantum Gravity and Strings Department of Mathematics and Applied Mathematics University of Cape Town Private Bag Rondebosch7700 South Africa

We generalize the quantum Geometric Tensor by replacing a Hamiltonian with a modular Hamiltonian. The symmetric part of the quantum Geometric Tensor provides a Fubini-Study metric, and its anti-symmetric sector gives a Berry curvature. Now the generalization or quantum Modular Geometric Tensor gives a Kinematic Space and a modular Berry curvature. Here we demonstrate the emergence by focusing on a spherical entangling surface. We also use the result of the identity Virasoro block to relate the connected correlator of two Wilson lines to the two-point function of a modular Hamiltonian. This result realizes a novel holographic entanglement formula for two intervals of a general separation. This formula does not only hold for a classical gravity sector but also quantum Gravity. The formula also provides a new quantum Information interpretation to the connected correlators of Wilson lines as the mutual information. Our study provides an opportunity to explore quantum Kinematic Space through quantum Modular Geometric Tensor and hence go beyond symmetry. Copyright © 2021, The Authors. All rights reserved.

关键词： Tensors

Thermodynamics of Kerr-Sen-AdS black holes in the restricted phase space

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Physical Review D 2023年第4期108卷 044045-044045页

作者： Md Sabir Ali Sushant G. Ghosh Anzhong Wang Lanzhou Center for Theoretical Physics Key Laboratory of Theoretical Physics of Gansu Province Lanzhou University Gansu Lanzhou 730000 China Key Laboratory of Quantum Theory and Applications MoE Lanzhou University Gansu Lanzhou 730000 China Institute of Theoretical Physics Research Center of Gravitation Lanzhou University Lanzhou 730000 China Centre for Theoretical Physics Jamia Millia Islamia New Delhi 110025 India Astrophysics and Cosmology Research Unit School of Mathematics Statistics and Computer Science University of KwaZulu-Natal Private Bag 54001 Durban 4000 South Africa GCAP-CASPER Physics Department Baylor University Waco 76798-7316 TX United States

We analyze the restricted phase-space thermodynamics (RPST) of Kerr-Sen-AdS black holes with the central charge C and its conjugate chemical potential μ but exclude the familiar PdV term in the first law of black hole thermodynamics. That gives rise to a new perspective on the thermodynamics of black holes. Using the scaling properties, we investigate the first law and the corresponding Euler formula. Such formalism has its beauty; for example, the mass is considered to be a homogeneous function of the extensive variables in the first order. In contrast, the intensive variables are of zeroth order. Because of the complicated expressions of the metric, we numerically calculate the critical values of the thermodynamic quantities. We find the phase-transition behavior of the free energy and other thermodynamic conjugate variables that appear in the first law. The RPST of the Kerr-Sen-AdS black holes is like that of the Reissner-Nordström-AdS and the Kerr-AdS black holes. Such notions of the phase transition behavior show that there should be some underlying universality in the RPST formalism.

关键词： Classical black holes quantum aspects of black holes quantum fields in curved spacetime

A composite measurement scheme for efficient quantum observable estimation

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arXiv 2023年

作者： Zhang, Zi-Jian Nakaji, Kouhei Choi, Matthew Aspuru-Guzik, Alán Department of Computer Science University of Toronto TorontoONM5S 2E4 Canada Vector Institute for Artificial Intelligence TorontoONM5S 1M1 Canada Department of Chemistry University of Toronto TorontoONM5G 1Z8 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 Materials Science & Engineering University of Toronto TorontoONM5S 3E4 Canada Department of Chemical Engineering & Applied Chemistry University of Toronto TorontoONM5S 3E5 Canada Canadian Institute for Advanced Research TorontoONM5G 1Z8 Canada

Estimation of the expectation value of observables is a key subroutine in quantum computing and is also the bottleneck of the performance of many near-term quantum algorithms. Many works have been proposed to reduce the number of measurements needed for this task and they provide different measurement schemes for generating the measurements to perform. In this paper, we propose a new approach, composite measurement scheme, which composes multiple measurement schemes by distributing shots to them with a trainable ratio. As an example of our method, we study the case where only Pauli measurements are allowed and propose Composite-LBCS (C-LBCS), a composite measurement scheme made by composing locally-biased classical shadows. We numerically demonstrate C-LBCS on molecular systems up to CO2 (30 qubits) and show that C-LBCS outperforms the previous state-of-the-art methods despite its simplicity. We also show that C-LBCS can be efficiently optimized by stochastic gradient descent and is trainable even when the observable contains a large number of terms. We believe our method opens up a reliable way toward efficient observable estimation on large quantum systems. © 2023, CC BY-NC-SA.

关键词： Stochastic systems

Tunable fragile topology in Floquet systems

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arXiv 2020年

作者： Zhang, Rui-Xing Yang, Zhi-Cheng Condensed Matter Theory Center Department of Physics University of Maryland College ParkMD20742-4111 United States Joint Quantum Institute University of Maryland College ParkMD20742 United States Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States

We extend the notion of fragile topology to periodically-driven systems. We demonstrate driving-induced fragile topology in two different models, namely, the Floquet honeycomb model and the Floquet π-flux square-lattice model. In both cases, we discover a rich phase diagram that includes Floquet fragile topological phases protected by crystalline rotation or mirror symmetries, Floquet Chern insulators, and trivial atomic phases, with distinct boundary features. Remarkably, the transitions between different phases can be feasibly achieved by simply tuning the driving amplitudes, which is a unique feature of driving-enabled topological phenomena. Moreover, corner-localized fractional charges are identified as a "smoking-gun" signal of fragile topology in our systems. Our work paves the way for studying and realizing fragile topology in Floquet systems. Copyright © 2020, The Authors. All rights reserved.

关键词： Topology

Improving the accuracy and efficiency of quantum connected moments expansions

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arXiv 2021年

作者： Claudino, Daniel Peng, Bo Bauman, Nicholas P. Kowalski, Karol Humble, Travis S. Oak Ridge National Laboratory Quantum Computing Institute Oak RidgeTN37831 United States Computer Science and Mathematics Oak Ridge National Laboratory Oak RidgeTN37831 United States Pacific Northwest National Laboratory Physical Sciences Division RichlandWA99352 United States Computational Sciences and Engineering Oak Ridge National Laboratory Oak RidgeTN37831 United States

The still-maturing noisy intermediate-scale quantum (NISQ) technology faces strict limitations on the algorithms that can be implemented efficiently. In quantum chemistry, the variational quantum eigensolver (VQE) algorithm has become ubiquitous, using the functional form of the ansatz as a degree of freedom, whose parameters are found variationally in a feedback loop between the quantum processor and its conventional counterpart. Alternatively, a promising new avenue has been unraveled by the quantum variants of techniques grounded on expansions of the moments of the Hamiltonian, among which two stand out: The connected moments expansion (CMX) [Phys. Rev. Lett. 58, 53 (1987)] and the Peeters-Devreese-Soldatov (PDS) functional [J. Phys. A 17, 625 (1984);Int. J. Mod. Phys. B 9, 2899], the latter based on the standard moments . Contrasting with VQE-based methods and provided the quantum circuit prepares a state with non-vanishing overlap with the true ground state, CMX often converges to the ground state energy, while PDS is guaranteed to converge by virtue of being variational. However, for a finite CMX/PDS order, the circuit may significantly impact the energy accuracy. Here we use the ADAPT-VQE algorithm to test shallow circuit construction strategies that are not expected to impede their implementation in the present quantum hardware while granting sizable accuracy improvement in the computed ground state energies. We also show that we can take advantage of the fact that the terms in the connected moments are highly recurring in different powers, incurring a sizable reduction in the number of necessary measurements. By coupling this measurement caching with a threshold that determines whether a given term is to be measured based on its associated scalar coefficient, we observe a further reduction in the number of circuit implementations while allowing for tunable accuracy. Copyright © 2021, The Authors. All rights reserved.

关键词： quantum chemistry

quantum autoencoders for communication-efficient quantum cloud computing

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arXiv 2021年

作者： Zhu, Yan Bai, Ge Wang, Yuexuan Li, Tongyang Chiribella, Giulio QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pokfulam Road Hong Kong HKU-Oxford Joint Laboratory for Quantum Information and Computation Zhejiang University Hangzhou China College of Computer Science and Technology Zhejiang University Hangzhou China Center on Frontiers of Computing Studies Peking University OxfordOX1 3QD United Kingdom School of Computer Science Peking University OxfordOX1 3QD United Kingdom Center for Theoretical Physics Massachusetts Institute of Technology OxfordOX1 3QD United Kingdom Department of Computer Science University of Oxford Parks Road OxfordOX1 3QD United Kingdom Perimeter Institute For Theoretical Physics 31 Caroline Street North WaterlooONN2L 2Y5 Canada The University of Hong Kong Shenzhen Institute of Research and Innovation Yuexing 2nd Rd Nanshan Shenzhen518057 China

In the model of quantum cloud computing, the server executes a computation on the quantum data provided by the client. In this scenario, it is important to reduce the amount of quantum communication between the client and the server. A possible approach is to transform the desired computation into a compressed version that acts on a smaller number of qubits, thereby reducing the amount of data exchanged between the client and the server. Here we propose quantum autoencoders for quantum gates (QAEGate) as a method for compressing quantum computations. We illustrate it in concrete scenarios of single-round and multi-round communication and validate it through numerical experiments. A bonus of our method is it does not reveal any information about the server’s computation other than the information present in the output. © 2021, CC BY.

关键词： Electronic data interchange

No-go theorem for device-independent security in relativistic causal theories

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Physical Review Research 2021年第3期3卷 033146-033146页

作者： R. Salazar M. Kamoń K. Horodecki D. Goyeneche D. Saha R. Ramanathan P. Horodecki Institute of Theoretical Physics and Astrophysics National Quantum Information Centre University of Gdansk 80-308 Gdansk Poland Faculty of Applied Physics and Mathematics National Quantum Information Centre Gdansk University of Technology 80-233 Gdansk Poland Institute of Informatics Faculty of Mathematics Physics and Informatics University of Gdansk 80-308 Gdansk Poland Institute of Physics Jagiellonian University 30-059 Krakow Poland International Centre for Theory of Quantum Technologies University of Gdansk Wita Stwosza 63 80-308 Gdansk Poland Departamento de Física Facultad de Ciencias Básicas Universidad de Antofagasta Casilla 170 Antofagasta Chile Center for Theoretical Physics Polish Academy of Sciences Aleja Lotników 32/46 02-668 Warsaw Poland Department of Computer Science University of Hong Kong Pokfulam Road Hong Kong

A fundamental question in device-independent quantum cryptography is to determine the minimal physical principle upon which the security of such a cryptographic protocol (such as for key distribution or for randomness generation) may be based. Since the seminal work on device-independent quantum key distribution by J. Barrett, L. Hardy, and A. Kent [Phys. Rev. Lett. 95, 010503 (2005)], a conjectured candidate for certification of device-independent security has been the principle of relativistic causality, namely the disallowance of causal loops. While this principle has thus far been equated with the no-signaling constraints, it has been shown recently that in multiparty Bell scenarios, the no-signaling constraints are sufficient but not necessary for relativistic causality, and a refined set of constraints has been proposed that more precisely capture the notion of relativistic causality. In this paper, we build upon this finding to show that, in contrast to the no-signaling constraints, the constraints of relativistic causality are not sufficient for certification of device-independent security. More specifically, we show that there exist correlations allowed by the causality principle that allow an adversary to gain complete information about the measurement outcomes of honest parties in any device-independent cryptographic protocol, thereby rendering the protocol completely insecure. As a tool to develop this adversarial attack strategy, we fully characterize the set of correlations allowed by relativistic causality in the tripartite Bell scenario of three parties, each performing two binary measurements, that may be of independent interest. We also demonstrate the difference between the relativistic causal correlations and those allowed by the usual no-signaling constraints by presenting explicit communication tasks wherein the two sets exhibit striking difference in their respective winning probabilities.

关键词： General relativity Nonlocality quantum communication quantum correlations in quantum information quantum cryptography