EPJ Quantum Technology最新文献

{"title":"Dynamic suppression of phase errors in optically pumped atomic magnetometers for applications in geomagnetic environments","authors":"Huanyu Zhou,&nbsp;Jin Li,&nbsp;Yi Zhang,&nbsp;Shuo Sun,&nbsp;Rongtong Zhu,&nbsp;Yan Xuan,&nbsp;Pengcheng Du,&nbsp;Zhuangsheng Zhu","doi":"10.1140/epjqt/s40507-026-00499-7","DOIUrl":"10.1140/epjqt/s40507-026-00499-7","url":null,"abstract":"<div><p>Phase error is one of the primary factors leading to deviations between the readings of alkali-metal optically pumped atomic magnetometers (OPAMs) operating in closed-loop mode and the true magnetic field values. Because the phase error varies significantly with both the magnitude of the measured magnetic field and the orientation of the probe relative to the field direction, it imposes a major limitation on the use of OPAMs in real geomagnetic environments. To address this issue, a rapid suppression method for phase error in closed-loop OPAM operation is proposed. Specifically, the azimuth, pitch, and rotation angles are employed to quantitatively characterize the spatial orientation of the measured magnetic field with respect to the probe, and the phase error is measured and calibrated under closed-loop conditions. Experimental results indicate that the phase error mainly arises from changes in the rotation angle and the magnitude of the magnetic field, and is essentially insensitive to variations in azimuth and pitch angles. Based on this calibration, the effectiveness of the proposed suppression method was verified. When the instantaneous fluctuation of the phase error is less than <i>π</i>/6, the method can suppress the phase error to within <i>π</i>/180 within one second, with negligible impact on the OPAM’s dynamic performance. This work provides a dynamic phase error suppression approach for OPAMs, refines the theoretical understanding of OPAM phase errors, and lays a solid foundation for their design and application in geomagnetic environments.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00499-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796467","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":"An arbitrated quantum signature scheme for classical information using entanglement swapping","authors":"Jason Lin,&nbsp;Mei-Yen Yen,&nbsp;Chia-Wei Tsai,&nbsp;Chun-Wei Yang","doi":"10.1140/epjqt/s40507-026-00497-9","DOIUrl":"10.1140/epjqt/s40507-026-00497-9","url":null,"abstract":"<div><p>Quantum signature protocols often rely on quantum states to carry signature information directly. However, they need SWAP tests, which require numerous copies to ensure accuracy and security, resulting in high implementation costs. This study proposes an arbitrated quantum signature protocol that incorporates classical information with entanglement swapping. Quantum states are converted into classical information immediately after measurement. The protocol does not rely on SWAP tests, avoids long-term storage of quantum signatures, and employs exclusive-OR operations and hash functions to process signature data. By leveraging a third-party arbitrator, it enables reliable identity verification of the signer and verifier, thereby guaranteeing unforgeability and nonrepudiation.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00497-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796552","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 algorithms for scheduling problems: a survey","authors":"Tino Werner,&nbsp;Freyja Ullinger","doi":"10.1140/epjqt/s40507-026-00494-y","DOIUrl":"10.1140/epjqt/s40507-026-00494-y","url":null,"abstract":"<div><p>Quantum algorithms have the potential to solve combinatorial optimization problems faster than classical algorithms. A particular example for combinatorial optimization problems are scheduling problems. This work provides summarizes quantum or quantum-inspired algorithms for scheduling problems, providing an overview of 20 years of research. We categorize the approaches by problem type and algorithm type. A condensation of the reviewed literature to the main ideas and details about the considered problem size, solvers and evaluation metrics enables a quick comparison with and placement into the current state of research for future works. We further critically assess the comparability of the reviewed literature and present crucial metrics for future comparison.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00494-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560239","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":"Performance-centric roadmap for building a superconducting quantum computer","authors":"R. Barends,&nbsp;F. K. Wilhelm","doi":"10.1140/epjqt/s40507-026-00495-x","DOIUrl":"10.1140/epjqt/s40507-026-00495-x","url":null,"abstract":"<div><p>One of the outstanding challenges in contemporary science and technology is building a quantum computer that is useful in applications. By starting from an estimate of the algorithm success rate, we can explicitly connect gate fidelity to quantum system size targets and define a quantitative roadmap that maximizes performance while avoiding distractions. We identify four distinct phases for quantum hardware and enabling technology development. The aim is to improve performance as we scale and increase the algorithmic complexity the quantum hardware is capable of running, the algorithmic radius, towards a point that sets us up for quantum advantage with deep noisy intermediate-scale quantum computing (NISQ) as well as building a large-scale error-corrected quantum computer (QEC). Our hope is that this document contributes to shaping the discussion about the future of the field.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00495-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147559887","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":"Rydberg-atom electrical-field sensors – a case study of dual use of quantum sensors","authors":"Jürgen Altmann,&nbsp;Harald Kübler","doi":"10.1140/epjqt/s40507-026-00489-9","DOIUrl":"10.1140/epjqt/s40507-026-00489-9","url":null,"abstract":"<div><p>Rydberg atoms in a room-temperature gas cell can be used for very sensitive detection of electrical fields in the megahertz to terahertz region. Sensors can be small, non-absorbing and are not destroyed by very strong fields with full-optical readout. Applications in communications, imaging and radar, and in metrology are foreseen. Military research is active, particularly in the USA, funding at first academic institutions, but increasingly development is contracted to commercial firms. There are similarities and differences between civilian and military applications, with interaction between both fields. Rydberg-atom electrical-field sensors are a general-purpose technology, and do not directly provide new offensive or threatening military options. No strong negative impacts on international security and peace are foreseen. Academic researchers have taken military funding readily.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00489-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560562","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 hybrid feature selector","authors":"Vadim Lopatkin,&nbsp;Asel Sagingalieva,&nbsp;Luca Lusnig,&nbsp;Tatjana Protasevich,&nbsp;Bernadette Behnke,&nbsp;Alexey Melnikov","doi":"10.1140/epjqt/s40507-026-00491-1","DOIUrl":"10.1140/epjqt/s40507-026-00491-1","url":null,"abstract":"<div><p>Unsupervised feature selection is essential for high-dimensional machine learning tasks, as it improves model quality and efficiency while providing interpretable insights into datasets. However, existing methods often struggle to simultaneously achieve robustness, reliability, interpretability, and computational efficiency. Furthermore, feature selection in quantum machine learning remains largely unexplored despite the potential of quantum approaches to capture complex feature interactions. In this work, we propose the Quantum Hybrid Feature Selector, a novel unsupervised feature selection framework that combines quantum-enhanced feature extraction with interpretable scoring algorithms. Our main contributions are threefold: we introduce a quantum hybrid autoencoder pipeline that couples feature extraction with feature ranking in the original input space, we define three scoring mechanisms: SHAP-based scoring, correlation-matrix scoring, and weight-based analysis, that relate latent features to original features without requiring external predictive models, and we provide comprehensive empirical evaluation on synthetic and real-world benchmarks with statistical validation. On Madelon-style synthetic datasets, our quantum SCM achieves up to 23.5% improvement in Mean Informative Rank and 9.7% improvement in Informative Ratio compared to classical alternatives, with all improvements statistically significant at <span>(p &lt; 0.001)</span>. On the Communities and Crime dataset with injected noise features, both quantum and classical SCM variants achieve near-perfect noise elimination, demonstrating effective denoising capability on real-world data. We also show that expert input is essential for evaluating feature selectors, as different methods emphasize distinct aspects of the data despite similar aggregate metrics. Finally, we evaluate QHFS under realistic hardware noise conditions using device-informed simulations based on IBM superconducting quantum processors, demonstrating graceful performance degradation and systematic improvement with increased shot budgets, which supports the practical viability of our approach on near-term quantum devices.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00491-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796551","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 kernel and HHL-based support vector machines for multi-class classification","authors":"Gabriela Pinheiro,&nbsp;Donovan M. Slabbert,&nbsp;Luis Kowada,&nbsp;Francesco Petruccione","doi":"10.1140/epjqt/s40507-026-00484-0","DOIUrl":"10.1140/epjqt/s40507-026-00484-0","url":null,"abstract":"<div><p>We compare two quantum approaches that use support vector machines for multi-class classification on a reduced Sloan Digital Sky Survey (<span>SDSS</span>) dataset: the quantum kernel-based QSVM and the Harrow-Hassidim-Lloyd least-squares SVM (HHL LS-SVM). Both one-vs-rest and two-step hierarchical classification schemes were implemented. The QSVM involves angle encoding of ten features, two unitary operator blocks consisting of rotational operator gates, and a projective measurement that projects the final state to the zero state. The HHL-based method involves solving a system of linear equations using the HHL algorithm and using the solution in a support vector machine approach. The results indicate that the QSVM outperforms HHL LS-SVM in most cases. HHL LS-SVM performs somewhat competitively in selected cases, particularly when isolating galaxies (majority), however, it also performs poorly in others, especially when isolating QSOs (minority). Comparisons with classical SVMs confirm that quantum and classical methods achieve broadly similar performance, with classical models performing slightly ahead overall. Scaling analysis reveals a trade-off: QSVM performance suffers from quadratic scaling with the number of samples and features, but benefits from explicit feature representation during training, while HHL LS-SVM scales essentially constantly, with moderate fluctuations, but suffers from limited representative elements. The HHL-based method is also highly noise-sensitive. These results suggest that QSVM performs better overall under the experimental conditions considered here and is likely to be more amenable to near-term hardware execution in terms of circuit depth and structure, while the more efficient scaling of HHL LS-SVM makes it a useful option for larger datasets beyond the NISQ era.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00484-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737670","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":"Evaluating radiation impact on transmon qubits in above and underground facilities","authors":"Francesco De Dominicis,&nbsp;Tanay Roy,&nbsp;Ambra Mariani,&nbsp;Mustafa Bal,&nbsp;Camilla Bonomo,&nbsp;Nicola Casali,&nbsp;Ivan Colantoni,&nbsp;Francesco Crisa,&nbsp;Angelo Cruciani,&nbsp;Fernando Ferroni,&nbsp;Dounia L. Helis,&nbsp;Lorenzo Pagnanini,&nbsp;Valerio Pettinacci,&nbsp;Roman Pilipenko,&nbsp;Stefano Pirro,&nbsp;Andrei Puiu,&nbsp;Alberto Ressa,&nbsp;Alexander Romanenko,&nbsp;Marco Vignati,&nbsp;David van Zanten,&nbsp;Shaojiang Zhu,&nbsp;Anna Grassellino,&nbsp;Laura Cardani","doi":"10.1140/epjqt/s40507-026-00490-2","DOIUrl":"10.1140/epjqt/s40507-026-00490-2","url":null,"abstract":"<div><p>Superconducting qubits can be sensitive to energy deposits caused by cosmic rays and ambient radioactivity. While previous studies have explored correlated effects in time and space due to cosmic ray interactions, we present the first direct comparison of a transmon qubit’s performance measured at two distinct sites: the above-ground SQMS facility (Fermilab, US) and the deep-underground Gran Sasso Laboratory (Italy). Despite the stark difference in radiation levels, we observe a similar average qubit relaxation time of approximately 80 microseconds at both locations. To investigate radiation-induced events, we employ a fast decay detection protocol, comparing the relative rates of events between the two environments. Although intrinsic noise remains the dominant source of errors in superconducting qubits, our analysis revealed a significant excess of radiation-induced events for high-coherence transmon qubits operated above-ground. Finally, using <i>γ</i>-ray sources with increasing activity levels, we evaluate the qubit response in a controlled low-background environment.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00490-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737667","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":"Magnetotactic bacterial populations studied with a Pound-Drever-Hall atomic magnetometer","authors":"María Hernández Ruiz,&nbsp;Christopher Kiehl,&nbsp;Vito Giovanni Lucivero,&nbsp;Morgan W. Mitchell","doi":"10.1140/epjqt/s40507-026-00487-x","DOIUrl":"10.1140/epjqt/s40507-026-00487-x","url":null,"abstract":"<div><p>We demonstrate an optically pumped magnetometer that monitors spin polarization using Pound Drever Hall (PDH) technique. The instrument exhibits a noise floor of 22.2 pT/<span>(sqrt{text{Hz}})</span> limited by optical photon shot noise, short-term instability of (30.8 pT/<span>(sqrt{text{Hz}})</span>)/<span>(sqrt{tau })</span> for averaging times <span>(tau le 0.2text{ s})</span>, instability below 70 pT for <span>(0.2text{ s} le tau le 20text{ s})</span> and a minimum instability of 47 pT at <span>(tau = 6text{ s})</span>. We apply the OPM to investigate the ability of magnetotactic bacteria (Magnetospirillum gryphiswaldense, MSR-1) to orient in externally applied magnetic fields. Observing an opaque, concentrated suspension, we detect deviations from exponential relaxation dynamics on second time-scales, which give information about the dispersion of bacterial magnetic moment and rotational damping coefficient. These parameters are observed to evolve as the population further concentrates due to evaporation and settling. To our knowledge, this is the first time such magnetic inhomogeneities and long-term relaxation deviations have been directly observed. This study showcases both the sensitivity and stability of our OPM and its potential for probing biophysical processes.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00487-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737500","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":"Suppression of spin-exchange decoherence for zero-field parametric modulation magnetometers","authors":"Shushan Gao,&nbsp;Bangcheng Han,&nbsp;Xiaoyu Li,&nbsp;Ziao Liu,&nbsp;Zhongyu Wang,&nbsp;Jianwei Sheng,&nbsp;Jixi Lu","doi":"10.1140/epjqt/s40507-026-00488-w","DOIUrl":"10.1140/epjqt/s40507-026-00488-w","url":null,"abstract":"<div><p>The zero-field atomic magnetometer is a type of high-sensitivity and miniaturized quantum sensing instrument, typically using continuous radio-frequency fields for parametric modulation to extract weak magnetic signals. However, this modulation induces additional spin-exchange relaxation that degrades spin coherence. Here we report a weak bias magnetic field-assisted pulsed field modulation scheme that significantly suppresses spin-exchange decoherence. The pulsed magnetic field reduces asynchronous phase accumulation by shortening the interaction time between the modulation field and the atomic spin ensemble, while the perpendicular bias field induces spin Larmor precession to periodically average modulation-induced relaxation, thereby suppressing the spin-exchange relaxation rate by a factor approximately equal to the pulse duty cycle. We develop a perturbative spin dynamics model to analyze the spin polarization response under this modulation. The experimental results demonstrate that this scheme overcomes the limitation imposed by the duty cycle threshold, suppresses the spin-exchange relaxation rate by more than 50%, and significantly enhances the magnetic response and sensitivity compared to conventional continuous modulation. This method can be extended to various alkali-metal spin systems relying on radio-frequency field operation, providing a new scheme for reducing modulation-induced spin-exchange decoherence.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00488-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737502","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}