npj Quantum Information最新文献_第2页

Unitary fault-tolerant encoding of Pauli states in surface codes 表面码中泡利态的统一容错编码

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-10-01 DOI: 10.1038/s41534-026-01362-4

Luis Colmenarez, Remmy Zen, Jan Olle, Florian Marquardt, Markus Müller

{"title":"Unitary fault-tolerant encoding of Pauli states in surface codes","authors":"Luis Colmenarez, Remmy Zen, Jan Olle, Florian Marquardt, Markus Müller","doi":"10.1038/s41534-026-01362-4","DOIUrl":"https://doi.org/10.1038/s41534-026-01362-4","url":null,"abstract":"In fault-tolerant quantum computation, the preparation of logical states is a ubiquitous subroutine, yet significant challenges persist even for the simplest states required. In the present work, we present a unitary, scalable, distance-preserving encoding scheme for preparing Pauli eigenstates in surface codes. Unlike previous unitary approaches whose fault-distance remains constant with increasing code distance, our scheme ensures that the protection offered by the code is preserved during state preparation. Building on strategies discovered by reinforcement learning for the surface-17 code, we generalize the construction to arbitrary code distances and both rotated and unrotated surface codes. The proposed encoding relies only on geometrically local gates, and is therefore fully compatible with planar 2D qubit connectivity, and it achieves circuit depth scaling as O(d), consistent with fundamental entanglement-generation bounds. We design explicit stabilizer-expanding circuits with and without ancilla-mediated connectivity and analyze their error-propagation behavior. Numerical simulations under depolarizing noise show that our unitary encoding without ancillas outperforms standard stabilizer-measurement-based schemes, reducing logical error rates by up to an order of magnitude. These results make the scheme particularly relevant for platforms such as trapped ions and neutral atoms, where measurements are costly relative to gates and idling noise is considerably weaker than gate noise. Our work bridges the gap between measurement-based and unitary encodings of surface-code states and opens new directions for distance-preserving state preparation in fault-tolerant quantum computation.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"11 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149087854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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

Anomalous weak values in a generalized Mach–Zehnder interferometer extracted directly from intensity measurements 直接从强度测量中提取广义马赫-曾德尔干涉仪中的异常弱值

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-28 DOI: 10.1038/s41534-026-01376-y

Ismaele V. Masiello, Hartmut Lemmel, Andreas Dvorak, Stephan Sponar, Yuji Hasegawa

{"title":"Anomalous weak values in a generalized Mach–Zehnder interferometer extracted directly from intensity measurements","authors":"Ismaele V. Masiello, Hartmut Lemmel, Andreas Dvorak, Stephan Sponar, Yuji Hasegawa","doi":"10.1038/s41534-026-01376-y","DOIUrl":"https://doi.org/10.1038/s41534-026-01376-y","url":null,"abstract":"Weak values provide a powerful framework for characterizing quantum systems. Their experimental extraction conventionally relies on weak conditioned von Neumann measurements, involving weak interactions and meter states that increase experimental complexity and often limit measurement efficiency. Here we introduce a method to fully characterize weak values in a generalized Mach–Zehnder interferometer employing neither meter states nor weak interactions. We experimentally demonstrate the technique in matter-wave interferometry. We identify anomalous weak values and, equivalently, negative quasiprobability distributions, which reflect the nonclassical behavior of the quantum system. The approach relies uniquely on intensity measurements at the output ports of the interferometer combined with controlled relative phase shifts between the paths. The absence of meter states enables considerable simplification of the setup and shorter measurement times, while preserving full access to weak values with comparable or increased accuracy. The scheme is directly applicable to a broad class of experiments involving two-level quantum systems.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"14 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149087814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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

Ten-second electron-spin coherence in isotopically engineered diamond 同位素工程金刚石中的十秒电子自旋相干性

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-28 DOI: 10.1038/s41534-026-01368-y

Takashi Yamamoto, Hendrik Benjamin van Ommen, Kai-Niklas Schymik, Beer de Zoeten, Shinobu Onoda, Seiichi Saiki, Takeshi Ohshima, Hadi Arjmandi-Tash, René Vollmer, Tim Hugo Taminiau

{"title":"Ten-second electron-spin coherence in isotopically engineered diamond","authors":"Takashi Yamamoto, Hendrik Benjamin van Ommen, Kai-Niklas Schymik, Beer de Zoeten, Shinobu Onoda, Seiichi Saiki, Takeshi Ohshima, Hadi Arjmandi-Tash, René Vollmer, Tim Hugo Taminiau","doi":"10.1038/s41534-026-01368-y","DOIUrl":"https://doi.org/10.1038/s41534-026-01368-y","url":null,"abstract":"Solid-state spin defects are a promising platform for quantum networks. A key requirement is to combine long ground-state spin-coherence times with a coherent optical transition for spin-photon entanglement. Here, we investigate the spin and optical coherence of single nitrogen-vacancy (NV) centres in (111)-grown isotopically engineered diamond. Our diamond-growth process yields a precisely controlled 13C concentration and low-ppb nitrogen concentrations. Combined with the mitigation of 50 Hz noise using a real-time feedforward scheme and tailored decoupling sequences, this enables record defect-electron-spin coherence times of T2 = 6.8(1) ms for a Hahn echo and of ({T}_{2}^{DD}=11.2(8)) s under dynamical decoupling. In addition, we observe coherent optical transitions with a near-lifetime-limited homogeneous linewidth of 16.9(4) MHz (222(3) MHz inhomogeneous broadening under 515nm illumination) and characterize the spectral diffusion dynamics. These results provide new avenues to investigate the incorporation of impurities in diamond and new opportunities for improved spin-qubit control for quantum networks and other quantum technologies.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"23 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2026-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149087852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 security of practical post-selection in Gaussian-modulated continuous-variable quantum key distribution 高斯调制连续变量量子密钥分发中实际后选择的安全性

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-26 DOI: 10.1038/s41534-026-01366-0

Adam Alderton,Amanda Weerasinghe,Muataz Alhussein,Adrian Wonfor,Richard Penty

引用次数: 0

Decoherence-protected entangling gates in a silicon carbide quantum node 碳化硅量子节点中的退相干保护纠缠门

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-26 DOI: 10.1038/s41534-026-01381-1

Shuo Ren,Rui-Jian Liang,Zhen-Xuan He,Ji-Yang Zhou,Wu-Xi Lin,Zhi-He Hao,Bing Chen,Tao Tu,Jin-Shi Xu,Chuan-Feng Li,Guang-Can Guo

引用次数: 0

Fully modulator-free architecture for quantum key distribution in scalable quantum networks 可扩展量子网络中量子密钥分发的完全无调制器架构

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-24 DOI: 10.1038/s41534-026-01377-x

Feng-Yu Lu,Xiao-Juan Huang,Yu-Xuan Fan,Shuang Wang,Zhen-Qiang Yin,Zi-Tao Liu,Wei Chen,De-Yong He,Guan-Jie Fan-Yuan,Guang-Can Guo,Zheng-Fu Han

{"title":"Fully modulator-free architecture for quantum key distribution in scalable quantum networks","authors":"Feng-Yu Lu,Xiao-Juan Huang,Yu-Xuan Fan,Shuang Wang,Zhen-Qiang Yin,Zi-Tao Liu,Wei Chen,De-Yong He,Guan-Jie Fan-Yuan,Guang-Can Guo,Zheng-Fu Han","doi":"10.1038/s41534-026-01377-x","DOIUrl":"https://doi.org/10.1038/s41534-026-01377-x","url":null,"abstract":"Abstract Quantum key distribution (QKD) networks represent a foundational step toward the future quantum internet and have become a focus of intensive research. By analogy with the architecture of classical optical networks, we can observe that the high-capacity backbone typically relies on complex external modulation, while the cost-sensitive access layer prefers simpler, more compact, and more economical direct modulation. As the cornerstone of quantum networks, today’s QKD networks share this backbone-access hierarchy, yet their implementations remain heavily reliant on external modulators, leaving a clear ecological niche unfilled for directly modulated QKD in the access layer. Here, we propose and experimentally demonstrate the first fully modulator-free, full-degree-of-freedom direct-modulation QKD architecture that fills this niche. The transmitter combines optical injection locking with coherent optical interference to achieve simultaneous phase and intensity control without external modulators, enabling arbitrary quantum-state preparation while preserving inherent compatibility with standard time-bin-encoding receivers. Built with relatively inexpensive laser diodes and passive optical components, our experimental implementation achieves a secure key rate of 4.78 kbps at 30 dB channel loss, matching the performance of conventional modulator-based systems. By filling the long-standing direct-modulation niche in the QKD ecosystem, this work delivers a practical solution to the access-layer deployment challenge and opens a viable new direction for compact, scalable QKD implementation.","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":"6 1","pages":""},"PeriodicalIF":7.6,"publicationDate":"2026-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149049417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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

Simulating and sampling from quantum circuits with 2D tensor networks 基于二维张量网络的量子电路模拟与采样

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-24 DOI: 10.1038/s41534-026-01372-2

Manuel S. Rudolph,Joseph Tindall

引用次数: 0

Complex-valued Quantum Neural Networks 复值量子神经网络

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-23 DOI: 10.1038/s41534-026-01369-x

Jingwei Wen,Ling Qian,Chao Zheng,Chuan Wang,Tiejun Wang

引用次数: 0

Publisher Correction: Asynchronous multi-photon interference for quantum networks 出版商更正：量子网络的异步多光子干扰

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-23 DOI: 10.1038/s41534-026-01378-w

Baghdasar Baghdasaryan,Karen Lozano-Méndez,Markus Leipe,Meritxell Cabrejo-Ponce,Sabine Häussler,Kaushik Joarder,Tim Gühring,Stephan Fritzsche,Thorsten A. Goebel,Ria G. Krämer,Stefan Nolte,Carlos Andres Melo Luna,Yoshiaki Tsujimoto,Fabian Steinlechner

引用次数: 0

Fragility of Magic State Distillation under Imperfect Measurements 不完全测量下状态蒸馏的脆弱性

IF 7.6 1区物理与天体物理

npj Quantum Information Pub Date : 2026-09-22 DOI: 10.1038/s41534-026-01373-1

Yunzhe Zheng,Yuanchen Zhao,Dong E. Liu

引用次数: 0