EPJ Quantum Technology最新文献

{"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}

{"title":"High-dimensional GHZ-based multi-party quantum key agreement: rigorous security, fairness, and loss tolerance","authors":"Hamza Sohail,&nbsp;Burhan Ul Islam Khan,&nbsp;Nur Fatin Liyana Mohd Rosely,&nbsp;Khang Wen Goh,&nbsp;Dwi Sudarno Putra,&nbsp;Abdul Raouf Khan,&nbsp;Mesith Chaimanee","doi":"10.1140/epjqt/s40507-026-00510-1","DOIUrl":"10.1140/epjqt/s40507-026-00510-1","url":null,"abstract":"<div><p>Multi-party quantum key agreement (MQKA) enables a group of mutually untrusted users to jointly establish a secret key with equal influence, a capability not provided by two-party quantum key distribution (QKD) and increasingly relevant for securing resilient infrastructure such as quantum-enabled smart grid networks and distributed cyber-physical systems. We present a high-dimensional Greenberger-Horne-Zeilinger (GHZ)-based MQKA that simultaneously targets rigorous security, provable fairness, and practical loss tolerance. The protocol distributes an <i>N</i>-partite <i>d</i>-level GHZ state in a star (with an optional star-of-stars hierarchy for large <i>N</i>) and maps each user’s contribution to local <span>(X_{d}^{a} Z_{d}^{b})</span> operations. A commit-then-reveal layer makes inputs binding and hiding, yielding equal influence fairness over <span>(mathbb{Z}_{d})</span> with a strict fair-abort guarantee. Composable secrecy is established via entropy bounds and a Devetak-Winter-style key rate analysis, strengthened by test-round statistics; we connect Mermin/Svetlichny-type correlators to min-entropy lower bounds and incorporate full leakage accounting and finite-key penalties. We model depolarizing, shift/phase (Weyl), amplitude-damping, erasures, detector efficiency, and dark counts, and derive closed-form mappings from device parameters to symbol/phase errors. Monte Carlo studies confirm that <span>(d&gt;2)</span> expands the positive-rate region and reduces the global survival required for a given throughput compared with qubit GHZ MQKA under identical conditions. We discuss potential photonic realizations (time-bin or frequency-bin encoding, discrete Fourier transform networks, and superconducting nanowire detectors) and architectural pathways toward larger <i>N</i> via hierarchical clustering, while acknowledging the significant technological challenges that would need to be overcome to realize high-dimensional multipartite entanglement experimentally. Overall, the scheme delivers higher efficiency per entangled state, rigorous fairness, and composable security with realistic noise and loss, addressing key gaps in current MQKA designs for resilient infrastructure.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00510-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147738495","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":"What makes a good quantum outreach video? An evaluation framework for a quantum video playlist","authors":"Daria Anttila,&nbsp;Philipp Bitzenbauer,&nbsp;Stina Scheer,&nbsp;Diana Tartaglia,&nbsp;Bart Folkers,&nbsp;Simon Goorney,&nbsp;Sohan Vartak,&nbsp;Jacob Sherson,&nbsp;Costanza Toninelli","doi":"10.1140/epjqt/s40507-025-00461-z","DOIUrl":"10.1140/epjqt/s40507-025-00461-z","url":null,"abstract":"<div><p>With increasing applications and industrialization of quantum-based technologies, quantum literacy is becoming progressively important for the general public. Online outreach videos are a popular tool due to their adaptability to complex contents. However, they can contain misinformation and foster inaccurate interpretations of quantum principles. The European Quantum Technology Flagship is addressing this by curating educational materials available to the public. Nevertheless, the community is still lacking an unambiguous method to assess the explanatory quality of quantum videos. Such a development would benefit teachers, science communicators and those who want to foster quantum knowledge outside of specialist endeavors. To close this gap, we iteratively developed an evaluative framework for quantum outreach videos, drawing on existing literature concerning educational videos. Two raters applied the final version of the framework to 20 videos (Cohen’s kappa 0.48). The results showed that some subcategories were coded rarely or not reliably enough, so a condensed version of the framework was introduced (Cohen’s kappa 0.59). We foresee an application of this framework to collections of quantum outreach videos. It illuminates the aspects to consider when creating such videos and highlights the importance of better defining how using certain subcategories can improve the explanatory quality of a video.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-025-00461-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147606430","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":"DuoQ-EpiNet: a dual-track quantum–classical convolutional neural network for EEG-based epilepsy seizure detection","authors":"Shivanya Shomir Dutta,&nbsp;Ishaan Milind Sawant,&nbsp;Sridevi S,&nbsp;Gurjit S. Randhawa,&nbsp;Rajiv Mistry,&nbsp;Jonathan Ortega,&nbsp;Anandan P,&nbsp;Indira B","doi":"10.1140/epjqt/s40507-026-00500-3","DOIUrl":"10.1140/epjqt/s40507-026-00500-3","url":null,"abstract":"<div><p>Epileptic seizure detection remains a critical challenge in clinical neurodiagnostics, particularly in low-data settings where EEG recordings are scarce. To address this, we propose DuoQ-EpiNet a dual-track hybrid framework that integrates quantum and classical deep learning models for robust seizure classification using the University of Bonn EEG dataset. In the first track, handcrafted statistical and spectral descriptors are extracted from the raw EEG signals and subsequently analyzed using a 1D Convolutional Neural Network (CNN) to learn discriminative temporal representations. In parallel, the second track with wavelet approach transforms the EEG signals into scalogram images, which are processed through a Hybrid Quanvolutional Classical Convolutional Neural Network (HQCNN) equipped with a Fixed Quantum Filter Circuit to generate expressive quantum feature maps followed by classical CNN. The latent representations obtained from both tracks are then fused and passed through fully connected layers to perform the final binary classification. Systematic comparison of the proposed DuoQ-EpiNet model by tweaking quantum hyperparameter based variants, state-of-the-art HQCNN architectures, as well as the best classical transfer learning models have demonstrated that the proposed model performs better than all evaluated variants. Among all evaluated configurations, the proposed DuoQ-EpiNet Binary Dual-Track (P-B-D) model achieved outstanding performance of 98.50% accuracy with its FQFC employed in Track 2 contrived with quantum hyperparameters of <span>(n_{shots} = 1000)</span> and <span>(n_{layers} = 1)</span>. Performance in data-scale studies ranging from 5% to 100% shows that DuoQ-EpiNet outperforms traditional baselines. Its generalization ability is confirmed by evaluation on the CHB-MIT scalp EEG dataset. The model maintains its stability at low noise densities with only slight performance deterioration, according to NISQ robustness study employing density matrix simulations with depolarizing, amplitude damping, phase damping, and readout noise.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00500-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147607239","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":"Enhancing Quantum Key Distribution via McEliece-based hybrid PQC-QKD architecture","authors":"Veeresh R. Maned,&nbsp;Satyabrat Rath,&nbsp;Jothi Ramalingam,&nbsp;Lakshmi Kuppusamy","doi":"10.1140/epjqt/s40507-026-00498-8","DOIUrl":"10.1140/epjqt/s40507-026-00498-8","url":null,"abstract":"<div><p>Quantum Key Distribution (QKD) offers information-theoretic security; however, its practicality is limited by an inherently low secret key rate. In this work, we propose a cryptographic enhancement of QKD by incorporating post-quantum public key encryption, namely Classic McEliece. We propose a novel hybrid PQC-QKD protocol named BBM that employs QC-LDPC based McEliece cryptosystem to encrypt the basis string in QKD, thereby skipping the sifting step and consequently improving the secret key rate. We only need to assume the short-term security of the McEliece cryptosystem during the protocol run to achieve the everlasting security of the distilled keys. Our analysis demonstrates that this integration not only enhances the achievable secret key rate by <span>(sim 2times )</span> in the BB84 protocol but also provides resistance against photon number splitting attack, and inherits a fallback mechanism in its design. This marks a significant improvement in terms of efficiency, security, and reliability over conventional BB84-like QKD protocols.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00498-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147560812","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":"Modulator-free, self-testing quantum random number generator","authors":"Ana Blázquez-Coído,&nbsp;Fadri Grünenfelder,&nbsp;Anthony Martin,&nbsp;Raphaël Houlmann,&nbsp;Hugo Zbinden,&nbsp;Davide Rusca","doi":"10.1140/epjqt/s40507-026-00501-2","DOIUrl":"10.1140/epjqt/s40507-026-00501-2","url":null,"abstract":"<div><p>Quantum random number generators (QRNGs) use the inherent unpredictability of quantum mechanics to generate true randomness, as opposed to classical random number generators. However, ensuring the authenticity of this randomness still requires robust verification. Self-testing QRNGs address this need by enabling the validation of the randomness produced based on the observed data from the experiment while requiring few assumptions. In this work, we present a practical, self-testing QRNG designed to operate with an untrusted measurement device and a partially characterized source, allowing the user to check the adequate functioning of the setup in real time. Our experiment yields a rate of certified random bits of 450 kbps.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00501-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796928","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":"BB84 a new hope enhanced QKD for secure email communication with additional quantum gates","authors":"Shiiv R S,&nbsp;Yuven Senthilkumar,&nbsp;V. Karthick","doi":"10.1140/epjqt/s40507-026-00493-z","DOIUrl":"10.1140/epjqt/s40507-026-00493-z","url":null,"abstract":"<div><p>The imminent realization of fault-tolerant quantum computing presents an existential threat to the cryptographic foundations of the modern digital economy. Algorithms such as Shor’s and Grover’s are poised to dismantle classical public-key encryption schemes like RSA (Shor in SIAM Rev. 41:303–332, 1999) and Elliptic Curve Cryptography (ECC) by solving integer factorization and discrete logarithm problems in polynomial time (Grover in A fast quantum mechanical algorithm for database search, 1996, arXiv [quant-ph]). This vulnerability endangers critical infrastructures, particularly secure email correspondence, which remains a primary vector for sensitive data exchange. Traditional defenses are proving inadequate against the “harvest now, decrypt later” strategies employed by sophisticated adversaries who stockpile encrypted traffic in anticipation of Q-Day (Venkatesh et al. in J. Sci. Eng. Technol. Manag. Sci. 2:567–577, 2025). Against this backdrop, this research introduces BB8-4, an enhanced Quantum Key Distribution (QKD) protocol specifically designed for secure email environments. The protocol advances the standard BB84 paradigm through two distinct innovations: the integration of a Hyper-Entropic 7-Gate State Preparation mechanism and an AI-Driven Dynamic Basis Selection engine.</p><p>Unlike traditional implementations that rely on a limited two-basis set, BB8-4 incorporates an expanded library of quantum gates - specifically Identity (I), Hadamard (H), Pauli-X, Pauli-Y, Pauli-Z, Phase (S), and the non-Clifford <span>(pi /8)</span> gate (T) - to fundamentally augment the indistinguishability and Von Neumann entropy of the transmitted quantum states. This “7-gate” approach forces an eavesdropper into a higher-dimensional guessing space, significantly degrading the information gain from intercept-resend attacks and raising the disturbance threshold required for detection. Furthermore, the protocol addresses the inherent 50% sifting inefficiency of standard QKD by employing a synchronized Deep Reinforcement Learning (DRL) agent to predict and align measurement bases between Alice and Bob without public disclosure (Kaldari et al. in Quantum reinforcement learning: Recent advances and future directions, 2025, arXiv [quant-ph]).</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00493-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147561065","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":"Decoding the surface code with a spatio-temporal transformer","authors":"Robert Joo","doi":"10.1140/epjqt/s40507-026-00492-0","DOIUrl":"10.1140/epjqt/s40507-026-00492-0","url":null,"abstract":"<div><p>Quantum error correction is a major area of research for building fault-tolerant quantum computers. Recently, machine learning has emerged as a compelling approach to quantum error decoding because of its flexibility and high performance compared to classical methods. In this work, we introduce a spatio-temporal transformer with graph Laplacian positional encodings and factorized latent attention to efficiently deal with the topological structure of the code and the temporal correlations across measurement rounds. We perform experiments with simulated data of the surface code for small distances and demonstrate the potential for our model.</p></div>","PeriodicalId":547,"journal":{"name":"EPJ Quantum Technology","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjqt/s40507-026-00492-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147796356","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":"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}