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PRX quantum 2025年第2期6卷 020322-020322页

作者： Nikhil Bansal Wai-Keong Mok Kishor Bharti Dax Enshan Koh Tobias Haug Institute of High Performance Computing (IHPC) Agency for Science Technology and Research (ASTAR) 1 Fusionopolis Way #16-16 Connexis Singapore 138632 Republic of Singapore Department of Physical Sciences Indian Institute of Science Education and Research (IISER) Mohali Sector 81 SAS Nagar Mohali Punjab 140306 India Institute for Quantum Information and Matter California Institute of Technology Pasadena California 91125 USA Quantum Innovation Centre (Q.InC) Agency for Science Technology and Research (ASTAR) 2 Fusionopolis Way Innovis #08-03 Singapore 138634 Republic of Singapore Centre for Quantum Engineering Research and Education TCG CREST Sector V Salt Lake Kolkata 700091 India Science Mathematics and Technology Cluster Singapore University of Technology and Design 8 Somapah Road Singapore 487372 Singapore Quantum Research Center Technology Innovation Institute Abu Dhabi United Arab Emirates

Pseudorandom states (PRSs) are state ensembles that cannot be efficiently distinguished from Haar-random states. However, the definition of PRSs has been limited to pure states and lacks robustness against noise. In this work, we introduce pseudorandom density matrices (PRDMs), ensembles of n-qubit states that are computationally indistinguishable from the generalized Hilbert-Schmidt ensemble (GHSE), which is constructed from (n+m)-qubit Haar random states with m qubits traced out. For m=0, PRDMs are equivalent to PRSs, whereas for m=ω(log n), PRDMs are computationally indistinguishable from the maximally mixed state. PRDMs with m=ω(log n) are robust to unital noise channels and separated in terms of security from PRS. PRDMs can disguise valuable quantum resources as trivial states. In particular, we construct pseudoresource state ensembles, which possess near-maximal entanglement, magic and coherence, but are computationally indistinguishable from resource-free states. PRDMs exhibit a pseudoresource gap of Θ(n) vs 0, surpassing previously found gaps. We also render EFI pairs, a fundamental cryptographic primitive, robust to strong mixed unitary noise. Our work has major implications on quantum resource theory. We show that entanglement, magic, and coherence cannot be efficiently tested, and that black-box resource distillation requires a superpolynomial number of copies. We also establish lower bounds on the purity needed for efficient testing and black-box distillation. Finally, we introduce memoryless PRSs, a noise-robust notion of PRS, which are indistinguishable to Haar random states for efficient algorithms without quantum memory, as well as noise-robust quantum money. Our work provides a comprehensive framework of pseudorandomness for mixed states, which yields powerful quantum cryptographic primitives and fundamental bounds on quantum resource theories.

关键词： quantum entanglement

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Discrimination of quantum States Under Locality Constraints in the Many-Copy Setting

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Communications in Mathematical Physics 2023年第1期404卷 151-183页

作者： Cheng, Hao-Chung Winter, Andreas Yu, Nengkun Department of Electrical Engineering and Graduate Institute of Communication Engineering National Taiwan University Tapei 106 Taiwan Department of Mathematics National Taiwan University Tapei 106 Taiwan Center for Quantum Science and Engineering National Taiwan University Tapei 106 Taiwan Physics Division National Center for Theoretical Sciences Taipei 10617 Taiwan Hon Hai (Foxconn) Quantum Computing Center New Taipei City 236 Taiwan ICREA-Institució Catalana de Recerca i Estudis Avançats Barcelona 08010 Spain Departament de Física Física Teòrica: Informaciò i Fenòmens Quàntics Universitat Autònoma de Barcelona Barcelona 08193 Spain Computer Science Department Stony Brook University New York NY United States Centre for Quantum Software and Information and Faculty of Engineering and Information Technology University of Technology Sydney Ultimo 2007 NSW Australia

We study quantum hypothesis testing between orthogonal states under restricted local measurements in the many-copy scenario. For testing arbitrary multipartite entangled pure state against its orthogonal complement state via the local operation and classical communication (LOCC) operation, we prove that the optimal average error probability always decays exponentially in the number of copies. Second, we provide a sufficient condition for the LOCC operations to achieve the same performance as the positive-partial-transpose (PPT) operations. We further show that testing a maximally entangled state against its orthogonal complement and testing extremal Werner states both fulfill the above-mentioned condition. Hence, we determine the explicit expressions for the optimal average error probability, the optimal trade-off between the type-I and type-II errors, and the associated Chernoff, Stein, Hoeffding, and strong converse exponents. Then, we show an infinite asymptotic separation between the separable (SEP) and PPT operations by providing a pair of states constructed from an unextendible product basis (UPB). The quantum states can be distinguished perfectly by PPT operations, while the optimal error probability, with SEP operations, admits an exponential lower bound. On the technical side, we prove this result by providing a quantitative version of the well-known statement that the tensor product of UPBs is a UPB. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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Real-time Simultaneous Dual Sensing of Temperature and Magnetic Field using NV-based Nano-diamonds

arXiv

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arXiv 2024年

作者： Sarkar, Sonia Agarwal, Namita Shishi, Dasika Saha, Kasturi Center for Research in Nano Technology and Science Indian Institute of Technology Bombay Maharashtra Mumbai India Department of Electrical Engineering Indian Institute of Technology Bombay Maharashtra Mumbai India Department of Physics Indian Institute of Technology Bombay Maharashtra Mumbai India Center of Excellence in Quantum Information Computing Science and Technology Indian Institute of Technology Bombay Mumbai Powai400076 India Indian Institute of Technology Bombay Mumbai Powai400076 India

quantum sensors based on Nitrogen Vacancy (NV) centers in diamond are highly capable of sensing multiple physical quantities. In this study, we use amplitude-modulated lock-in detection of optically detected magnetic resonance of NV nanodiamonds (NVND) to investigate the link between temperature (T) and the zero-field splitting parameter (D) and also the relationship between magnetic field values and the difference of resonance frequencies. We also present NVNDs' capacity to simultaneously sense both thermal and magnetic fields in real time. This dual-sensing approach is beneficial for studying magnetic materials whose magnetization depends on temperature and the applied magnetic field, such as certain ferromagnetic and ferrimagnetic materials. Integrating real-time thermal and magnetic field measurements provides unique opportunities for failure analysis in the integrated circuit (IC) industry and for studying thermodynamic processes in cell physiology. The ability to concurrently monitor temperature and magnetic field variations offers a powerful toolset for advancing precision diagnostics and monitoring in these fields. Copyright © 2024, The Authors. All rights reserved.

关键词： Ferrimagnetic materials

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State-Dependent Mobility Edge in Kinetically Constrained Models

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PRX quantum 2024年第4期5卷 040348-040348页

作者： Manthan Badbaria Nicola Pancotti Rajeev Singh Jamir Marino Riccardo J. Valencia-Tortora Department of Physics Indian Institute of Technology (Banaras Hindu University) Varanasi 221005 India AWS Center for Quantum Computing Pasadena California 91125 USA California Institute of Technology Pasadena California 91125 USA Institut für Physik Johannes Gutenberg-Universität Mainz D-55099 Mainz Germany Pritzker School of Molecular Engineering University of Chicago Chicago Illinois 60637 USA

In this work, we show that the kinetically constrained quantum East model lies between a quantum scarred and a many-body localized system featuring an unconventional type of mobility edge in the spectrum. We name this scenario the state-dependent mobility edge: while the system does not exhibit a sharp separation in energy between thermal and nonthermal eigenstates, the abundance of nonthermal eigenstates results in slow entanglement growth for many initial states, such as product states, below a finite energy density. We characterize the state-dependent mobility edge by looking at the complexity of classically simulating dynamics using tensor networks for system sizes well beyond those accessible via exact diagonalization. Focusing on initial product states, we observe a qualitative change in the dynamics of the bond dimension needed as a function of their energy density. Specifically, the bond dimension typically grows polynomially in time up to a certain energy density, where we locate the state-dependent mobility edge, enabling simulations for long times. Above this energy density, the bond dimension typically grows exponentially, making the simulation practically unfeasible beyond short times, as generally expected in interacting theories. We correlate the polynomial growth of the bond dimension to the presence of many nonthermal eigenstates around that energy density, a subset of which we compute via tensor networks. The outreach of our findings encompasses quantum sampling problems and the efficient simulation of quantum circuits beyond Clifford families.

关键词： Tensors

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HiMA: Hierarchical quantum Microarchitecture for Qubit-Scaling and quantum Process-Level Parallelism

arXiv

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arXiv 2024年

作者： Zhou, Qi Mei, Zi-Hao Shi, Han-Qing Guo, Liang-Liang Yang, Xiao-Yan Wang, Yun-Jie Xu, Xiao-Fan Xue, Cheng Kong, Wei-Cheng Wang, Jun-Chao Wu, Yu-Chun Chen, Zhao-Yun Guo, Guo-Ping CAS Key Laboratory of Quantum Information School of Physics University of Science and Technology of China Anhui Hefei230026 China Origin Quantum Computing Company Limited Anhui Hefei China Laboratory for Advanced Computing and Intelligence Engineering Henan Zhengzhou450001 China Institute of Artificial Intelligence Hefei Comprehensive National Science Center Anhui Hefei230088 China

quantum computing holds immense potential for addressing a myriad of intricate challenges, which is significantly amplified when scaled to thousands of qubits. However, a major challenge lies in developing an efficient and scalable quantum control system. To address this, we propose a novel Hierarchical MicroArchitecture (HiMA) designed to facilitate qubit scaling and exploit quantum process-level parallelism. This microarchitecture is based on three core elements: (i) discrete qubit-level drive and readout, (ii) a process-based hierarchical trigger mechanism, and (iii) multiprocessing with a staggered triggering technique to enable efficient quantum process-level parallelism. We implement HiMA as a control system for a 72-qubit tunable superconducting quantum processing unit, serving a public quantum cloud computing platform, which is capable of expanding to 6144 qubits through three-layer cascading. In our benchmarking tests, HiMA achieves up to a 4.89× speedup under a 5-process parallel configuration. Consequently, to the best of our knowledge, we have achieved the highest CLOPS (Circuit Layer Operations Per Second), reaching up to 43,680, across all publicly available platforms. Copyright © 2024, The Authors. All rights reserved.

关键词： Qubits

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Nonreciprocal Bundle Emissions of quantum Entangled Pairs

arXiv

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arXiv 2024年

作者： Bin, Qian Jing, Hui Wu, Ying Nori, Franco Lü, Xin-You School of Physics Institute for Quantum Science and Engineering Huazhong University of Science and Technology Wuhan Institute of Quantum Technology Wuhan430074 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Theoretical Quantum Physics Laboratory Cluster for Pioneering Research RIKEN Wakoshi Saitama351-0198 Japan Center for Quantum Computing RIKEN Wakoshi Saitama351-0198 Japan Physics Department The University of Michigan Ann ArborMI48109-1040 United States

Realizing precise control over multiquanta emission is crucial for quantum information processing, especially when integrated with advanced techniques of manipulating quantum states. Here, by spinning the resonator to induce the Sagnac effect, we can obtain nonreciprocal photon-phonon and photon-magnon super-Rabi oscillations under conditions of optically driving resonance transitions. Opening dissipative channels for such super-Rabi oscillations enables the realization of directional bundle emissions of entangled photon-phonon pairs and photon-magnon pairs by transferring pure multiquanta state to bundled multiquanta outside of the system. This nonreciprocal emission is a flexible switch that can be controlled with precision, and simultaneous emissions of different entangled pairs (such as photon-phonon or photon-magnon pairs) can even emerge but in opposite directions by driving the resonator from different directions. This ability to flexibly manipulate the system allows us to achieve directional entangled multiquanta emitters, and has also potential applications for building hybrid quantum networks and on-chip quantum communications. © 2024, CC BY.

关键词： Photons

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ANF: Attention-Based Noise Filtering Strategy for Unsupervised Few-Shot Classification 18th

ANF: Attention-Based Noise Filtering Strategy for Unsupervis...

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18th Pacific Rim International Conference on Artificial Intelligence, PRICAI 2021

作者： Ni, Guangsen Zhang, Hongguang Zhao, Jing Xu, Liyang Yang, Wenjing Lan, Long Institute for Quantum Information and State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Changsha410073 China Systems Engineering Institute AMS Beijing China

ISBN: (纸本)9783030893699

How to learn concepts from few-shot samples remains an open challenge in the deep learning era. The previous meta-learning methods require a large number of annotated samples in the training phase, which still contributes to high manual-labeling costs. In this paper, we propose a unsupervised few-shot learning framework and pointed out that negative queue constructed via randomly sampling contains many false-negative samples (noise), which has negative impacts on the model’s generalized performance especially when only few samples are available. Specially, we propose an Attention-based Noise Filtering (ANF) strategy to make momentum contrastive loss more applicable to few-shot learning scenario. In addition, we also propose a dynamic momentum update method, which can greatly improve the classification accuracy. Our evaluations demonstrate state-of-the-art unsupervised few-shot learning performance, which is comparable to supervised baseline models. © 2021, Springer Nature Switzerland AG.

关键词： Computer vision

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Coherence Crossover Dynamics in the Strong Coupling Regime

SSRN

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SSRN 2022年

作者： Ali, Md. Manirul Dinakaran, Rohith Radhakrishnan, Chandrashekar Centre for Quantum Science and Technology Chennai Institute of Technology Chennai600069 India Computer Science and Engineering Department Chennai Institute of Technology Chennai600069 India Centre for Quantum Information Communication and Computing Indian Institute of Technology Madras Chennai600036 India

The transient dynamics of quantum coherence of Gaussian states are investigated. The state is coupled to an external environment which can be described by a Fano-Anderson type Hamiltonian. Solving the quantum Langevin equation, we obtain the Greens functions which are used to compute the time evolved first and second moments of the quadrature operators. From the quadrature operator moments, we construct the covariance matrix which is used to measure the coherence in the system. The coherence is estimated using the relative entropy of coherence measure. We consider three different classes of spectral densities in our analysis viz., the Ohmic, the sub-Ohmic, and the super-Ohmic densities. In our work, we study the dynamics of the coherent state, squeezed state, and displaced squeezed state. For all these states we observe that when the coupling with the system and the environment is weak, the coherence monotonically decreases and eventually vanishes in a long time. Thus all the states exhibit Markovian evolution in the weak coupling limit. In the strong coupling limit, the dynamics for the initial period is Markovian and after a certain period, it becomes non-Markovian where we observe an environmental backaction on the system. To confirm the non-Markovianity of the evolution we use a detection method based on Bure's distance formula. Thus in the strong coupling limit, we observe a dynamical crossover from Markovian nature to non-Markovian behavior. This crossover is very abrupt under some environmental conditions and for some parameters of the quantum state. Using a quantum master equation approach we verify the crossover from the dynamics of the dissipation and fluctuation parameters and the results endorse those obtained from coherence dynamics. © 2022, The Authors. All rights reserved.

关键词： quantum optics

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quantum-Inspired VCSEL-based Optical Parallel Feedback System for Large-Scale Combinatorial Optimization

Quantum-Inspired VCSEL-based Optical Parallel Feedback Syste...

引用

OptoElectronics and Communications Conference, OECC

作者： Soon Thor Lim Dewen Zhang Zifeng Yuan Thanh Xuan Hoang Ching Eng Png Aaron Danner Electronics and Photonics Nano & Quantum Photonics/AI Institute of High Performance Computing (IHPC) Agency for Science Technology and Research (A⋆STAR) Singapore Singapore Dept. of Electrical and Computer Engineering National University of Singapore Singapore Singapore

ISBN: (数字)9798350308396

ISBN: (纸本)9798350308402

Photonic Ising computers hypothetically allow fast solutions to intractable combinatorial optimization problems. We have identified a possible physical implementation involving arrays of injection-locked Vertical Cavity Surface Emitting Lasers and an optical feedback mechanism which allows all-to-all bit connectivity without separate components along each connection path. Time-domain simulations indicate system stability up to at least 16 bits. Experimental realization of polarization switching in injection-locked VCSELs is also demonstrated as a proof-of-concept.

关键词： Computers Stimulated emission Optical feedback Qubit Stability analysis Vertical cavity surface emitting lasers Time-domain analysis Semiconductor laser arrays Optimization Optical arrays

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Low-Depth Hamiltonian Simulation by an Adaptive Product Formula

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Physical Review Letters 2023年第4期130卷 040601-040601页

作者： Zi-Jian Zhang Jinzhao Sun Xiao Yuan Man-Hong Yung Department of Physics Southern University of Science and Technology Shenzhen 518055 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Center on Frontiers of Computing Studies Peking University Beijing 100871 China Clarendon Laboratory University of Oxford Parks Road Oxford OX1 3PU United Kingdom Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China

Various Hamiltonian simulation algorithms have been proposed to efficiently study the dynamics of quantum systems on a quantum computer. The existing algorithms generally approximate the time evolution operators, which may need a deep quantum circuit that is beyond the capability of near-term noisy quantum devices. Here, focusing on the time evolution of a fixed input quantum state, we propose an adaptive approach to construct a low-depth time evolution circuit. By introducing a measurable quantifier that characterizes the simulation error, we use an adaptive strategy to learn the shallow quantum circuit that minimizes that error. We numerically test the adaptive method with electronic Hamiltonians of the H2O and H4 molecules, and the transverse field Ising model with random coefficients. Compared to the first-order Suzuki-Trotter product formula, our method can significantly reduce the circuit depth (specifically the number of two-qubit gates) by around two orders while maintaining the simulation accuracy. We show applications of the method in simulating many-body dynamics and solving energy spectra with the quantum Krylov algorithm. Our work sheds light on practical Hamiltonian simulation with noisy-intermediate-scale-quantum devices.

关键词： quantum algorithms quantum simulation

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