EPJ Quantum Technology最新文献

{"title":"Reinforcement learning an entangling operation on spin qubits","authors":"Mohammad Abedi,&nbsp;Markus Schmitt","doi":"10.1140/epjqt/s40507-026-00528-5","DOIUrl":"10.1140/epjqt/s40507-026-00528-5","url":null,"abstract":"<div><p>High-fidelity control of one- and two-qubit gates past the error correction threshold is an essential ingredient for scalable quantum computing. We present a reinforcement learning (RL) approach to find entangling protocols for semiconductor-based singlet-triplet qubits in a double quantum dot. Despite the presence of realistically modelled experimental constraints, such as various noise contributions and finite rise-time effects, we demonstrate that an RL agent can yield performative protocols, while avoiding the model-biases of traditional gradient-based methods. We optimise our RL approach for different regimes and tasks, including training from simulated process tomography reconstruction of unitary gates, and investigate the nuances of RL agent design.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00528-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148173540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimal constant-cost implementations of Clifford operations using global interactions","authors":"Jonathan Nemirovsky,&nbsp;Lee Peleg,&nbsp;Amit Ben Kish,&nbsp;Yotam Shapira","doi":"10.1140/epjqt/s40507-026-00520-z","DOIUrl":"10.1140/epjqt/s40507-026-00520-z","url":null,"abstract":"<div><p>We investigate quantum circuits built from arbitrary single-qubit operations combined with programmable all-to-all multiqubit entangling gates that are native to, among other systems, trapped-ion quantum computing platforms. We report a constant-cost of no more than four applications of such Clifford entangling multiqubit gates to realize any sequence of Clifford operations of any length, without ancillae, which is the theoretically optimal gate count cost. We do this by implementing any sequence of CNOT gates of any length with four applications of such gates, without ancillae, and show that the extension to general Clifford operations incurs no additional cost. We investigate the required qubit drive power that is associated with our implementation and show that it is lower than that of a standard approach. Our work introduces a practical and computationally efficient algorithm to realize these compilations.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00520-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148614381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Resource-efficient quantum optimization via higher-order encoding","authors":"Frederik Koch,&nbsp;Shahram Panahiyan,&nbsp;Rick Mukherjee,&nbsp;Joseph Doetsch,&nbsp;Dieter Jaksch","doi":"10.1140/epjqt/s40507-026-00526-7","DOIUrl":"10.1140/epjqt/s40507-026-00526-7","url":null,"abstract":"<div><p>Quantum approaches to combinatorial optimization problems (COPs) are often limited by the resource demands of Quadratic Unconstrained Binary Optimization (QUBO) encodings, which enlarge circuits through penalty terms and increase qubit and gate counts. We show that Higher-Order Unconstrained Binary Optimization (HUBO) enables a more resource-efficient formulation. Our method systematically constructs HUBO Hamiltonians and, compared to a QUBO formulation in benchmarks on Gate Assignment (GAP), Maximum k-Colorable Subgraph (MkCS), and Integer Programming (IP) problems, significantly reduces qubit requirements and decreases total CNOT gate counts by at least 89.6% for all tested instances. These results highlight HUBO as a practical alternative for quantum optimization on near-term devices. To promote adoption, we release an open-source Python library that automates HUBO model construction, extends beyond the examples presented in this work, and broadens access to resource-efficient quantum optimization.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00526-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148009879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deterministic high-dimensional entangled states analysis and quantum teleportation","authors":"Fang-Fang Du,&nbsp;Ling-Hui Li,&nbsp;Chen Huang,&nbsp;Zhuo-Ya Bai,&nbsp;Qiu-Lin Tan","doi":"10.1140/epjqt/s40507-026-00525-8","DOIUrl":"10.1140/epjqt/s40507-026-00525-8","url":null,"abstract":"<div><p>Entanglement in high-dimensional systems plays a vital role in quantum information processing (QIP), as it extends the available Hilbert space, supports the manipulation of more intricate information, and broadens the scope of implementable quantum operations. In the paper, we present a deterministic scheme for the four-dimensional two-qudit Bell entangled state analysis for the four-photon system in the polarization degree of freedom, resorting to the weak cross-Kerr nonlinearity and some linear optical components. In our scheme, the analysis of four-dimensional Bell entangled state is constructed by three-photon Toffoli gate and quantum nondemolition detectors (QND₁ and QND₂). By phase shifts of the coherent beams, the 16 orthogonal four-dimensional two-qudit Bell states can be completely distinguished from each other. The proposal can be extended to the four-dimensional three-qudit entangled state analysis and <i>n</i>-qudit entangled state analysis. In addition, our deterministic scheme for high-dimensional entangled state analysis can be applied to high-dimensional quantum teleportation, including both uncontrolled and controlled quantum teleportation protocols. Moreover, our scheme can achieve high fidelity and efficiency, further broadening its applicability in high-dimensional QIP.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00525-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Channel superposition mitigates photon loss errors in quantum illumination","authors":"Fei Li,&nbsp;Xiao-Wei Li,&nbsp;Oscar Dahlsten","doi":"10.1140/epjqt/s40507-026-00523-w","DOIUrl":"10.1140/epjqt/s40507-026-00523-w","url":null,"abstract":"<div><p>In quantum illumination, the probe and idler photons are entangled, and both are jointly measured at the end. The entanglement between the probe and idler photons enhances the detection performance per unit average photon number in the probe mode, particularly in low-reflectivity and high-noise scenarios. However, photon loss degrades the absolute detection performance and progressively reduces the performance gain relative to optimal classical strategies by diminishing non-classical correlations. To address this, we employ a channel superposition framework that encompasses two types of channel superposition protocols: indefinite causal order (ICO) and path superposition with a disjoint environment (PS-DE). Under the effective erasure/fading loss model adopted for the low-brightness regime, our analytical and numerical analysis based on the quantum Chernoff bound shows that both ICO and PS-DE can, in principle, achieve an advantage. The advantage persists as long as non-zero interference remains, reverting to the performance of standard quantum illumination once the interference is completely suppressed. Crucially, within this model, the ICO protocol is significantly more robust, maintaining a tighter upper bound on the error probability than standard quantum illumination and the PS-DE approach. This performance hierarchy is rooted in their fundamental structures: ICO exploits a shared environment to generate stronger quantum interference, while PS-DE, relying on disjoint environments, offers a more experimentally tractable, albeit weaker, alternative.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00523-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quantum entanglement for magnetometry","authors":"Vladimir Slepnev,&nbsp;Azat Gubaydullin,&nbsp;Valerii Vinokur","doi":"10.1140/epjqt/s40507-026-00524-9","DOIUrl":"10.1140/epjqt/s40507-026-00524-9","url":null,"abstract":"<div><p>Quantum metrology promises enhanced precision by harnessing entanglement and quantum algorithms. Yet, realizing such gains on current noisy quantum hardware remains a significant challenge. Here, we investigate quantum-enhanced magnetometry using phase estimation algorithms on superconducting quantum processors the IQM Garnet and Rigetti Ankaa-3. We experimentally compare the performance of different entangled, parallel and combined sensing strategies. While the entangled states should provide improvements in sensitivity in ideal conditions, we find that their advantage is less in practice on currently available systems. Instead, partitioning qubits into smaller entangled subsets and operating them in parallel achieves near-optimal sensitivity. We derive a general expression for magnetometric precision as a function of total qubit number and subset entanglement size, based on the attenuation of the system, identifying optimal configurations under realistic noise constraints.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00524-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Benchmarking hybrid quantum-safe cryptography over real-world infrastructures","authors":"Jaime S. Buruaga,&nbsp;Juan P. Brito,&nbsp;Vicente Martin","doi":"10.1140/epjqt/s40507-026-00521-y","DOIUrl":"10.1140/epjqt/s40507-026-00521-y","url":null,"abstract":"<div><p>Advances in quantum computing pose a significant threat to the widely used Public Key Infrastructure (PKI). The two leading technologies to address this challenge are Post-Quantum Cryptography and Quantum Key Distribution. A promising approach is the hybridization of these technologies – combining their respective strengths while mitigating their limitations – and integrating them with the cryptographic mechanisms used today to enhance crypto-agility and facilitate transitioning to a quantum-safe infrastructure. However, changing current network protocols to quantum-safe alternatives is not just a matter of security: their efficiency and scalability must also be demonstrated within real-world telecommunications infrastructures to ensure their practical adoption. In this work, we present the first long-running test with detailed measurements of a suite of hybrid quantum-safe protocols that integrate classical cryptography, PQC, and QKD within a production environment (MadQCI). Using standardized protocols and interfaces and employing Transport Layer Security (TLS) as the base protocol for real-world comparison, this study demonstrates the efficiency and scalability of the proposed solution in deployed heterogeneous networks. These results mark a significant step towards the widespread adoption of quantum-safe hybrid protocols and contribute to clarifying the path toward their future standardization in next-generation telecommunications networks.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00521-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148466113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measurement and research of cavity loss on squeezed light enhancement mechanism","authors":"Haoran Lv,&nbsp;Bozheng Xing,&nbsp;Xiujie Fang,&nbsp;Bowen Sun,&nbsp;Wenyi Huang,&nbsp;Danyue Ma,&nbsp;Wenhao Zhao,&nbsp;Jianli Li,&nbsp;Bangcheng Han","doi":"10.1140/epjqt/s40507-026-00518-7","DOIUrl":"10.1140/epjqt/s40507-026-00518-7","url":null,"abstract":"<div><p>In the process of generating squeezed light based on parameter down-conversion, the optical cavity loss affects the performance of the squeezed light. In this article, we propose a new method for measuring cavity loss in locking conditions, which has the advantage of being able to accurately measure cavity loss under optical cavity operating conditions. Based on this measurement method, we study the influence of cavity loss on SHG and OPO processes. The experiment results indicate that the reducing the additional cavity loss, such as cavity loss caused by thermal noise can effectively improve the performance of SHG and OPO cavities, and enhance the squeezing degree of squeezed light sources, which will restrict the further improvement of the squeezed light. The research results of this article are of great significance for the generation of high-performance squeezed light and quantum precision sensing based on quantum enhancement.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00518-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148008605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A scalable architecture for quantum information processors: qubit partitioning, placement, and scheduling for minimized circuit latency","authors":"Zahra Alimohammadi,&nbsp;Naser Mohammadzadeh,&nbsp;Saeid Seyedi,&nbsp;Hatam Abdoli","doi":"10.1140/epjqt/s40507-026-00519-6","DOIUrl":"10.1140/epjqt/s40507-026-00519-6","url":null,"abstract":"<div><p>Proposing an architecture that effectively compensates for physical hardware inefficiencies through redundant resources is a key challenge in quantum computer design. Although the representation of quantum systems is currently limited to tens of qubits, scaling existing small scale laboratory systems into large scale quantum computers capable of solving meaningful practical problems remains a primary research objective. Focusing on this issue, this paper proposes a scalable architecture for quantum information processors. Physical design, one of the two main processes in quantum computer design, transforms a circuit netlist into a technology specific layout. Quantum mapping comprising partitioning, placement, scheduling, and routing is an essential part of this process, and these stages are inherently interdependent. In this research, considering the dependencies between these stages, we present an Integer Linear Programming (ILP) model for qubit partitioning and placement, determining the optimal module and physical location for each qubit. Furthermore, we propose a heuristic approach for the placement and scheduling of quantum operators on a scalable, modular, universal ion trap quantum computer (MUSIQC), aiming to minimize circuit execution delay. Qubit routing is performed using a greedy strategy. For evaluation, the proposed method was applied to both Ripple-Carry Adder and Carry-Lookahead Adder circuits. Experimental results demonstrate that the proposed approach reduces the average circuit delay by approximately 58.98% for Ripple-Carry Adder circuits and 33% for Carry-Lookahead Adder circuits compared to the best existing method. These results underscore the effectiveness of our integrated framework, where ILP-based partitioning optimizes for dominant operational costs, while our subsequent resource-aware scheduler actively manages parallelism and contention to achieve the minimal overall circuit execution delay.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00519-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148008608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase projection errors in rf-driven optically pumped magnetometers","authors":"Zoran D. Grujić,&nbsp;Marija Ćurčić,&nbsp;Aleksandra Kocić,&nbsp;Antoine Weis,&nbsp;Theo Scholtes","doi":"10.1140/epjqt/s40507-026-00517-8","DOIUrl":"10.1140/epjqt/s40507-026-00517-8","url":null,"abstract":"<div><p>We investigate the phase relationship between the oscillating (rf) excitation field and the detected (light) power modulation in scalar rf-driven optically pumped magnetometers (OPMs), in particular in the <span>(M_{x})</span> configuration. While the static dependence of the demodulation phase on the direction of the external static magnetic field vector can be largely mitigated by aligning the oscillating rf field along the light propagation direction, we demonstrate that a dynamic (transient) phase response arises under magnetic field tilts. We analytically solve the corresponding modified Bloch equation and confirm agreement with experimental observations obtained using an <span>(M_{x})</span> magnetometer incorporating a paraffin-coated Cs vapor cell. The results reveal fundamental limitations of <span>(M_{x})</span> magnetometers regarding response time and accuracy, in particular when employed with active electronic feedback, such as a phase-locked loop. Therefore, this work is highly relevant to important magnetometry applications where the direction of the quasi-static magnetic field of interest is unknown <i>a priori</i> or varies over time, or in measurements requiring a large detection bandwidth. Such conditions are encountered in applications such as geomagnetic surveying, particularly with mobile platforms.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00517-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147829930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}