Quantum最新文献_第8页

Critical spin models from holographic disorder 来自全息无序的临界自旋模型

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-22 DOI: 10.22331/q-2025-07-22-1808

Dimitris Saraidaris, Alexander Jahn

引用次数: 0

Dictionary-based Block Encoding of Sparse Matrices with Low Subnormalization and Circuit Depth 基于字典的低次归一化和电路深度稀疏矩阵分块编码

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-22 DOI: 10.22331/q-2025-07-22-1805

Chunlin Yang, Zexian Li, Hongmei Yao, Zhaobing Fan, Guofeng Zhang, Jianshe Liu

{"title":"Dictionary-based Block Encoding of Sparse Matrices with Low Subnormalization and Circuit Depth","authors":"Chunlin Yang, Zexian Li, Hongmei Yao, Zhaobing Fan, Guofeng Zhang, Jianshe Liu","doi":"10.22331/q-2025-07-22-1805","DOIUrl":"https://doi.org/10.22331/q-2025-07-22-1805","url":null,"abstract":"Block encoding severs as an important data input model in quantum algorithms, enabling quantum computers to simulate non-unitary operators effectively. In this paper, we propose an efficient block-encoding protocol for sparse matrices based on a novel data structure, called the dictionary data structure, which classifies all non-zero elements according to their values and indices. Non-zero elements with the same values, lacking common column and row indices, belong to the same classification in our block-encoding protocol's dictionary. When compiled into the $textit{{U(2), CNOT}}$ gate set, the protocol queries a $2^n times 2^n$ sparse matrix with $s$ non-zero elements at a circuit depth of $mathcal{O}(log(ns))$, utilizing $mathcal{O}(n^2s)$ ancillary qubits. This offers an exponential improvement in circuit depth relative to the number of system qubits, compared to existing methods [1,2] with a circuit depth of $mathcal{O}(n)$. Moreover, in our protocol, the subnormalization, a scaled factor that influences the measurement probability of ancillary qubits, is minimized to $sum_{l=0}^{s_0}vert A_lvert$, where $s_0$ denotes the number of classifications in the dictionary and $A_l$ represents the value of the $l$-th classification. Furthermore, we show that our protocol connects to linear combinations of unitaries $(LCU)$ and the sparse access input model $(SAIM)$. To demonstrate the practical utility of our approach, we provide several applications, including Laplacian matrices in graph problems and discrete differential operators.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"18 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144677389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Cramér-Rao approach and global quantum estimation of bosonic states cram<s:1> - rao方法与玻色子态的全局量子估计

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-22 DOI: 10.22331/q-2025-07-22-1806

Masahito Hayashi, Yingkai Ouyang

引用次数: 0

Estimation of Quantum Fisher Information via Stein’s Identity in Variational Quantum Algorithms 变分量子算法中基于Stein恒等式的量子Fisher信息估计

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-21 DOI: 10.22331/q-2025-07-21-1798

Mourad Halla

引用次数: 0

Quick design of feasible tensor networks for constrained combinatorial optimization 约束组合优化可行张量网络的快速设计

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-21 DOI: 10.22331/q-2025-07-21-1799

Hyakka Nakada, Kotaro Tanahashi, Shu Tanaka

{"title":"Quick design of feasible tensor networks for constrained combinatorial optimization","authors":"Hyakka Nakada, Kotaro Tanahashi, Shu Tanaka","doi":"10.22331/q-2025-07-21-1799","DOIUrl":"https://doi.org/10.22331/q-2025-07-21-1799","url":null,"abstract":"Quantum computers are expected to enable fast solving of large-scale combinatorial optimization problems. However, their limitations in fidelity and the number of qubits prevent them from handling real-world problems. Recently, a quantum-inspired solver using tensor networks has been proposed, which works on classical computers. Particularly, tensor networks have been applied to constrained combinatorial optimization problems for practical applications. By preparing a specific tensor network to sample states that satisfy constraints, feasible solutions can be searched for without the method of penalty functions. Previous studies have been based on profound physics, such as U(1) gauge schemes and high-dimensional lattice models. In this study, we devise to design feasible tensor networks using elementary mathematics without such a specific knowledge. One approach is to construct tensor networks with nilpotent-matrix manipulation. The second is to algebraically determine tensor parameters. We showed mathematically that such feasible tensor networks can be constructed to accommodate various types of constraints. For the principle verification, we numerically constructed a feasible tensor network for facility location problem, to find much faster construction than conventional methods. Then, by performing imaginary time evolution, feasible solutions were always obtained, ultimately leading to the optimal solution.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"14 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144669725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Entanglement and Stabilizer entropies of random bipartite pure quantum states 随机二部纯量子态的纠缠态和稳定熵

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-21 DOI: 10.22331/q-2025-07-21-1797

Daniele Iannotti, Gianluca Esposito, Lorenzo Campos Venuti, Alioscia Hamma

引用次数: 0

Probing quantum complexity via universal saturation of stabilizer entropies 通过稳定熵的普遍饱和探测量子复杂性

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-21 DOI: 10.22331/q-2025-07-21-1801

Tobias Haug, Leandro Aolita, M.S. Kim

{"title":"Probing quantum complexity via universal saturation of stabilizer entropies","authors":"Tobias Haug, Leandro Aolita, M.S. Kim","doi":"10.22331/q-2025-07-21-1801","DOIUrl":"https://doi.org/10.22331/q-2025-07-21-1801","url":null,"abstract":"Nonstabilizerness or `magic' is a key resource for quantum computing and a necessary condition for quantum advantage. Non-Clifford operations turn stabilizer states into resourceful states, where the amount of nonstabilizerness is quantified by resource measures such as stabilizer Rényi entropies (SREs). Here, we show that SREs saturate their maximum value at a critical number of non-Clifford operations. Close to the critical point SREs show universal behavior. Remarkably, the derivative of the SRE crosses at the same point independent of the number of qubits and can be rescaled onto a single curve. We find that the critical point depends non-trivially on Rényi index $alpha$. For random Clifford circuits doped with T-gates, the critical T-gate density scales independently of $alpha$. In contrast, for random Hamiltonian evolution, the critical time scales linearly with qubit number for $alpha$ $gt$$1$, while it is a constant for $alpha$$lt$$1$. This highlights that $alpha$-SREs reveal fundamentally different aspects of nonstabilizerness depending on $alpha$: $alpha$-SREs with $alpha$$lt$$1$ relate to Clifford simulation complexity, while $alpha$$gt$$1$ probe the distance to the closest stabilizer state and approximate state certification cost via Pauli measurements. As technical contributions, we observe that the Pauli spectrum of random evolution can be approximated by two highly concentrated peaks which allows us to compute its SRE. Further, we introduce a class of random evolution that can be expressed as random Clifford circuits and rotations, where we provide its exact SRE. Our results opens up new approaches to characterize the complexity of quantum systems.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"26 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144669726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Averaging gate approximation error and performance of Unitary Coupled Cluster ansatz in Pre-FTQC Era 前ftqc时代统一耦合簇分析的平均门逼近误差和性能

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-21 DOI: 10.22331/q-2025-07-21-1800

Kohdai Kuroiwa, Yuya O. Nakagawa

{"title":"Averaging gate approximation error and performance of Unitary Coupled Cluster ansatz in Pre-FTQC Era","authors":"Kohdai Kuroiwa, Yuya O. Nakagawa","doi":"10.22331/q-2025-07-21-1800","DOIUrl":"https://doi.org/10.22331/q-2025-07-21-1800","url":null,"abstract":"Fault-tolerant quantum computation (FTQC) is essential to implement quantum algorithms in a noise-resilient way, and thus to enjoy advantages of quantum computers even with presence of noise. In FTQC, a quantum circuit is decomposed into universal gates that can be fault-tolerantly implemented, for example, Clifford+$T$ gates. Here, $T$ gate is usually regarded as an essential resource for quantum computation because its action cannot be simulated efficiently on classical computers and it is experimentally difficult to implement fault-tolerantly. Practically, it is highly likely that only a limited number of $T$ gates are available in the near future. Pre-FTQC era, due to the constraint on available resources, it is vital to precisely estimate the decomposition error of a whole circuit. In this paper, we propose that the Clifford+$T$ decomposition error for a given quantum circuit containing a large number of quantum gates can be modeled as the depolarizing noise by averaging the decomposition error for each quantum gate in the circuit, and our model provides more accurate error estimation than the naive estimation. We exemplify this by taking unitary coupled-cluster (UCC) ansatz used in the applications of quantum computers to quantum chemistry as an example. We theoretically evaluate the approximation error of UCC ansatz when decomposed into Clifford+$T$ gates, and the numerical simulation for a wide variety of molecules verified that our model well explains the total decomposition error of the ansatz. Our results enable the precise and efficient usage of quantum resources in the early-stage applications of quantum computers and fuel further research towards what quantum computation can achieve in the upcoming future.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"52 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144669727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Field theory for monitored Brownian SYK clusters 监测布朗SYK星团的场论

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-14 DOI: 10.22331/q-2025-07-14-1794

Anastasiia Tiutiakina, Hugo Lóio, Guido Giachetti, Jacopo De Nardis, Andrea De Luca

引用次数: 0

End-to-end switchless architecture for fault-tolerant photonic quantum computing 用于容错光子量子计算的端到端无开关架构

IF 6.4 2区物理与天体物理

Quantum Pub Date : 2025-07-14 DOI: 10.22331/q-2025-07-14-1796

Paul Renault, Patrick Yard, Raphael C. Pooser, Miller Eaton, Hussain Asim Zaidi

{"title":"End-to-end switchless architecture for fault-tolerant photonic quantum computing","authors":"Paul Renault, Patrick Yard, Raphael C. Pooser, Miller Eaton, Hussain Asim Zaidi","doi":"10.22331/q-2025-07-14-1796","DOIUrl":"https://doi.org/10.22331/q-2025-07-14-1796","url":null,"abstract":"Photonics represents one of the most promising approaches to large-scale quantum computation with millions of qubits and billions of gates, owing to the potential for room-temperature operation, high clock speeds, miniaturization of photonic circuits, and repeatable fabrication processes in commercial photonic foundries. We present an end-to-end architecture for fault-tolerant continuous variable (CV) quantum computation using only passive on-chip components that can produce photonic qubits above the fault tolerance threshold with probabilities above 90%, and encodes logical qubits using physical qubits sampled from a distribution around the fault tolerance threshold. By requiring only low photon number resolution, the architecture enables the use of high-bandwidth photodetectors in CV quantum computing. Simulations of our qubit generation and logical encoding processes show a Gaussian cluster squeezing threshold of 12 dB to 13 dB. Additionally, we present a novel magic state generation protocol which requires only 13 dB of cluster squeezing to produce magic states with an order of magnitude higher probability than existing approaches, opening up the path to universal fault-tolerant quantum computation at less than 13 dB of cluster squeezing.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":"29 1","pages":""},"PeriodicalIF":6.4,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144629686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0