EPJ Quantum Technology最新文献

Quantum dot intermediate band solar cells (QD-IBSCs) have attracted significant attention as a promising approach to enhance solar cell efficiency by two-step two-photon absorption. The Shockley-Queisser limitation has been resolved by using QD-IBSCs, which was a challenge for solar cell commercialization. In this study, we employed an efficient approach in QD-IBSCs to enhance the solar cell efficiency by using the truncated conical quantum dot (TCQD) shape. The effect on the performance of TCQD-IBSC has been symmetrically examined by varying the geometrical parameters, band gap, electron affinity, doping concentration, absorber layer thickness, and carrier mobility. Interestingly, TCQD-IBSC showed an efficiency of 51.1%, which decreases to 12.3%, 14.1%, and 26% with the increase in bandgap, doping concentration, and electron affinity, respectively. Notably, we improved the short-circuit current density by increasing the thickness of the absorber layer to 330 nm and carrier mobility to 4000 cm²V⁻¹s⁻¹, which led to higher power conversion efficiencies (PCE) of the solar cell. Moreover, a trade-off relation has been observed between QD size and interdot spacing. The PCE is gradually decreased from 49 % to 41.4 % with the increase in temperature. This model structure provides a new direction toward the achievement of high-efficiency TCQD-IBSCs and may promote the development of next-generation solar cells with high efficiency.

With the ongoing advances in noisy intermediate-scale quantum hardware, variational quantum algorithms have demonstrated significant potential in a range of quantum applications. However, obtaining high-performance, shallow-parameterized quantum circuits typically requires repeated optimization of the gate parameters over a large set of candidate circuits, resulting in prohibitively high evaluation costs. To address this challenge, this study proposes a novel predictor-based quantum architecture search (PQAS-ZX) method that leverages ZX-calculus. In this approach, a quantum circuit is first represented as a ZX diagram that supports multi-step equivalent simplifications at the diagram level. By applying these equivalence transformations, multiple circuit variants that share the same performance metric are generated, thereby significantly expanding the training dataset and enhancing the ability of the predictor to manage diverse circuit structures. ZX diagrams offer more flexible characterizations of multi-qubit entanglement and phase interactions, as well as higher-level equivalent transformations, compared with the state-of-the-art predictor-based quantum architecture search with graph measures (PQAS-GM). Numerical simulations of three variational quantum eigensolver tasks, namely the transverse-field Ising, Heisenberg, and BeH₂ molecular models, demonstrated that PQAS-ZX required only approximately 80.9%, 82.9%, and 76.1% of the queries required by PQAS-GM, respectively, to achieve the same probability of reaching the target ground-state energy. These results highlight the advantage of using ZX diagrams to identify high-quality circuits efficiently and alleviate the evaluation burden of quantum architecture searches.

Background

Introducing advanced quantum mechanics (QM) and quantum technology (QT) concepts to high school students is a global priority aimed at developing a quantum-literate workforce for the growing QT industry. However, high school-initiated QT outreach programs embedded in sustainable, school-led activities remain rare, with most researcher-led programs treating classroom integration as an afterthought. This study addresses this gap by reporting findings from a school-initiated, fully online quantum education STEM & Research Internship Program (SRIP) for Filipino high school students.

Method and Theoretical Framework

We employed a single-group quasi-experimental pre-post research design, collecting data via a mixed-methods approach using validated concept inventories and students’ daily journal entries. The program was guided by a theoretical framework integrating the discipline–culture paradigm of physics knowledge (for curriculum design) with the cognitive apprenticeship model (for curriculum implementation). Twenty high-achieving students (11 males, 9 females; Grades 9–11) from a STEM-focused Philippine high school participated.

Results and Conclusion

Results indicate increased knowledge of QM and QT concepts and improved attitudes towards QM among students following completion of the quantum education SRIP. Findings highlight the program’s positive educational impact and its novelty as the first school-initiated, fully online quantum outreach initiative in the Philippines, with potential for global adoption.

Quantum technologies and computing are an emerging area which offers a new paradigm to solve complex problems using the principles of quantum mechanics, where classical computing faces limits. Due to the advantages of quantum computers, today, there are several industries focusing on different aspects of quantum technologies based on their physics to explore the most efficient and useful platform for implementing applications. Since the scope of the quantum companies is diverse, it is important to understand the education, skills, and qualifications required for different job roles, as this will aid global educational institutions in constructing concentrated disciplines in this field. This paper provides a detailed critical analysis of different job descriptions for education, skills and qualifications. Most of the qubit modalities, such as superconducting, semiconducting, topological, nitrogen-vacancy centres, ion-traps, neutral atoms, and photonics, have been covered. Additionally, quantum software domains such as quantum machine learning, cryptography and error corrections have been discussed with fields such as quantum sensors and metrology. Finally, based on the patterns, recommendations are given to enable better preparation of skills and infrastructure for educational institutes and individuals who would like to pursue a career in the field of quantum technologies.

Quantum key distribution (QKD) promises theoretically secure communication. However, it encounters challenges in implementation security and performance due to inevitable device imperfections. Since the proposal of measurement-device-independent (MDI) QKD, the critical step toward practical security is to secure QKD with imperfect sources. The source imperfections manifest as state-preparation uncertainty (SPU) in various aspects, e.g., encoding uncertainty, intensity fluctuation, and imperfect vacuum states. Here, we perform an MDI-QKD experiment and achieve both high practical security and superior performance. We address the general form of SPU and guarantee a tight estimation of the secret key rate based on the operator dominance method. We achieve secure key distribution over 303.37 km, which not only represents the farthest distance in experiments involving SPU but also considers the most SPU scenarios. Our experimental results represent a significant step toward promoting practical and secure quantum communication.

Superconducting quantum computing has emerged as a leading platform in the pursuit of practical quantum computers, driven by rapid advances from industry, academia, and government initiatives. This review examines the state of superconducting quantum technology, with emphasis on qubit design, processor architecture, scalability, and supporting quantum software. We compare the hardware strategies and performance milestones of key players—including IBM Quantum, Google Quantum AI, Rigetti Computing, Intel Quantum, QuTech, and Oxford Quantum Circuits—highlighting innovations in qubit coherence, control, and system integration. Landmark demonstrations such as quantum supremacy experiments are discussed alongside progress toward real-world applications in the noisy intermediate-scale quantum (NISQ) era. Beyond hardware, attention is given to the broader software and service ecosystem, including quantum programming frameworks, operating environments, and cloud-accessible platforms such as Amazon Braket, Azure Quantum, and OriginQ Cloud, which enable remote access and algorithm development. Persistent challenges in superconducting quantum computing—such as error correction, system stability, and large-scale integration—are assessed in light of emerging approaches aimed at fault-tolerant quantum computing. As the field moves from the NISQ era toward fault-tolerant quantum computing, we capture the defining hardware achievements and characteristics of current superconducting processors, while examining the ongoing efforts and challenges in overcoming NISQ-era limitations. These developments offer critical insights into the path toward scalable quantum systems and their transformative impact on future technologies, while also underscoring the strategic and societal considerations that require balancing innovation with responsible oversight and thoughtful governance.

We present a design for a multi-channel optically pumped zero-field magnetometer utilizing a 200-μm-thick Rubidium vapor cell. The vapor cell and its housing are designed to reduce the minimal distance between a magnetic sample and the sensing volume to about 1 mm, to optimize the effective spatial resolution. The thin vapor cell, filled with 2 atm of nitrogen as a buffer gas reduces the volume across which the magnetic field is averaged. The vapor cell is fully illuminated by a single laser beam, and the transmitted light is imaged onto a 4 x 4 photodiode array, allowing for simultaneous measurement of a magnetic field distribution with up to 16 channels. The performance of the magnetometer is studied for all channels. It is shown that the sensor can operate in the spin-exchange relaxation-free regime with a projected photon-shot noise limited noise floor of about 1 pT/Hz^1/2 for a sensitive voxel size of approximately 600 μm x 600 μm x 200 μm.

The bin packing problem (BPP), a classical NP-hard combinatorial optimization challenge, has emerged as a promising application for quantum computing. In this work, we tackle the one-dimensional BPP (1dBPP) using a digitized counterdiabatic quantum approximate optimization algorithm (DC-QAOA) that incorporates counterdiabatic (CD) driving to achieve a 40% higher feasibility ratio than standard QAOA, while reducing quantum resource requirements. We investigate three ansatz schemes -DC-QAOA, CD-inspired ansatz, and CD-mixer ansatz - each integrating CD terms with distinct combinations of cost and mixer Hamiltonians, resulting in different DC-QAOA variants. Numerical simulations demonstrate that these DC-QAOA variants maintain solution accuracy with less than 5% variance across varying iteration numbers, circuit depths, and Hamiltonian step sizes. Moreover, they require approximately 7 to 8 times fewer measurements to achieve comparable precision under the same parameter variations. Experimental validation on a 10-item 1dBPP instance using IBM quantum computers shows the CD-mixer ansatz achieves five times more feasibility solutions and greater robustness against NISQ noise. Collectively, these results establish DC-QAOA as a resource-efficient framework for combinatorial optimization on near-term quantum devices.

This study proposes the first multiparty-to-multiparty mediated quantum secret sharing (M2M-MQSS) protocol within a restricted quantum environment. Unlike existing fully quantum secret sharing (QSS) protocols, this protocol allows protocol participants with limited quantum capabilities—including (1) measuring a single qubit in the Z-basis and (2) performing a single-qubit unitary operation, Hadamard operation—to participate, significantly reducing implementation costs. By employing one-way qubit transmission, the proposed MMQSS protocol not only simplifies the quantum communication process but also effectively defends against quantum Trojan horse attacks. The correctness and security analyses demonstrate that the proposed M2M-MQSS protocol is robust against various well-known attack strategies. Simulation experiments confirm the feasibility of the protocol for various numbers of participants. It maintains high levels of efficiency and security even as the number of participants increases. Moreover, compared with existing protocols, the proposed M2M-MQSS protocol lowers the barrier to practical quantum communication deployment by reducing the quantum resources required for protocol participants.