Advanced quantum technologies最新文献

In the current quantum computing paradigm, significant focus is placed on the reduction or mitigation of quantum decoherence. When designing new quantum processing units, the general objective is to reduce the amount of noise qubits are subject to, and in algorithm design, a large effort is underway to provide scalable error correction or mitigation techniques. Yet some previous work has indicated that certain classes of quantum algorithms, such as quantum machine learning, may, in fact, be intrinsically robust to or even benefit from the presence of a small amount of noise. Here, we demonstrate that noise levels in quantum hardware can be effectively tuned to enhance the ability of quantum neural networks to generalize data, acting akin to regularisation in classical neural networks. As an example, we consider two regression tasks, where, by tuning the noise level in the circuit, we demonstrated improvement of the validation mean squared error loss. Moreover, we demonstrate the method's effectiveness by numerically simulating QNN training on a realistic model of a noisy superconducting quantum computer.

Bose-Einstein condensates (BECs) provide an ideal platform for exploring novel quantum states (QTs) in synthetic spin-orbit coupling (SOC). In article number 2500431, Yun Liu and Zu-Jian Ying analyse the interplay of SOC with other interactions and potential geometry by BECs in concentric annular traps. Various exotic QTs emerge, including facial-makeup states, fissure states, stripe states, half-disk states, half-skyrmion fence, etc. Peculiar density-phase separation is noticed. The study illustrates manipulations of exotic QTs and supplies abundant quantum resources for potential applications.

Research on the quantum nature of matter and light has flourished in recent years, as the field has grown for theorists and experimentalists alike. New research directions, such as the study of novel phases in quantum materials, have laid the ground for new foundational theories and future quantum technologies. In particular, novel topological materials and superconducting hybrid systems are promising for the development of novel superconductors and quantum computers.

This Focus Issue aims to highlight some of the latest achievements in the field of quantum matter. It includes 3 Reviews, 1 Perspective, and 3 Research Articles on a range of topics, including single-photon emitters for quantum technologies, topological quantum materials, and quantum sensing and metrology:

Rare-Earth Doped Thin Films for Optical Quantum Technologies (Philippe Goldner et al., 10.1002/qute.202500026): A Review article on rare earth-doped thin films—materials that are highly promising for use in on-chip photonic circuits thanks to their excellent coherence properties. The integration of rare-earth thin films into photonic platforms could potentially enable photonic quantum technologies, such as optical quantum memories, which are relevant for communications and processing.

Cuprate twistronics for quantum hardware (Nicola Poccia et al., 10.1002/qute.202500203): A topical Review on the emerging field of cuprate twistronics, which involves stacking and twisting ultrathin layers of cuprate superconductors. This technique creates Moiré patterns and new electronic states, uncovering new opportunities in both applied (e.g., quantum hardware) and fundamental physics.

Quantum spin Hall effects in van der Waals materials (Qiong Ma et al., 10.1002/qute.202500327): A Review of the Quantum Spin Hall (QSH) effect in two-dimensional van der Waals (vdW) materials. The QSH effect is promising for the development of low-power electronics and topological quantum computing. The article explores the main developments in the field, emerging research directions, as well as experimental challenges.

Beyond kagome: p-bands in kagome metals (Alexander Tsirlin et al., 10.1002/qute.202500336): A Perspective arguing that p-bands (electron bands from non-transition metals) play a critical, often overlooked, role in the electronic instabilities, such as charge-density waves and superconductivity, observed in kagome lattice metals.

High-purity single-photon emission in the telecom O-band from droplet-epitaxy InAs quantum dots integrated into a GaAs/AlGaAs planar microcavity on vicinal GaAs(111) (Battulga Munkhbat et al., 10.1002/qute.202500159): A Research article on developing a reliable source of single photons in the telecom O-band (a critical wavelength for fibre communication) using InAs quantum dots grown via droplet epitaxy. Single-photon emission from such sources could potentially be u

In article number 2500263, Zu-Jian Ying, Simone Felicetti, Daniel Braak, and co-workers propose a practical solution by introducing a feasible neutral quartic term to the standard two-photon quantum Rabi model. This modification prevents spectral collapse, turning it into a well-defined quantum phase transition. This work offers a paradigmatic approach to overcoming instability in NLLMIs, paving the way towards critical quantum sensing applications.

The quantum spin Hall (QSH) effect, first predicted in graphene by Kane and Mele in 2004, has become a key platform for exploring spin–orbit coupling, topology, and electronic interactions. Initially demonstrated in quantum wells, the field has expanded with the emergence of van der Waals (vdW) materials. This review focuses on vdW systems, which provide unique advantages: exposed surfaces allow comprehensive spectroscopic and microscopic detection of the QSH state; mechanical stacking enables symmetry tuning and proximity effects; and moiré engineering introduces new topology and strong correlations. We highlight two monolayer families, 1T'-MX₂ and $��{\mathrm{MM}}^{\prime }�X_4�$, represented by WTe₂ and TaIrTe₄, respectively, which host QSH phases in close proximity to other quantum states including excitonic insulators, charge density waves, and superconductivity. Their low symmetry and topology produce rich quantum geometrical responses, from nonlinear Hall to circular photogalvanic effects. We also discuss moiré systems that combine topology with flatband physics, enabling spontaneous symmetry breaking and transitions from QSH to quantum anomalous Hall (QAH) states. Recent observations of fractionalized QAH and QSH states mark a major advance in condensed matter physics. Finally, we outline potential applications, such as nonlinear Hall–based microwave rectification and fractional states for topological quantum computing.

A hardware-efficient optimization scheme is presented for quantum chemistry calculations, utilizing the Sampled Quantum Diagonalization (SQD) method. This algorithm, optimized SQD (SQDOpt), combines the classical Davidson method technique with added multi-basis measurements to optimize a quantum Ansatz on hardware using a fixed number of measurements per optimization step. This addresses the key challenge associated with other quantum chemistry optimization protocols, namely Variational Quantum Eigensolver (VQE), which must measure in hundreds to thousands of noncommuting Pauli terms to estimate energy on hardware, even for molecules with less than 20 qubits. Numerical results for various molecules, including hydrogen chains, water, and methane, demonstrate the efficacy of this method compared to classical and quantum variational approaches, and the performance on the ibm-cleveland quantum hardware is confirmed, where instances are found where SQDOpt either matches or exceeds the solution quality of practical implementations of noiseless VQE. A runtime scaling indicates that SQDOpt on quantum hardware is competitive with classical state-of-the-art methods, with a crossover point of 1.5 seconds/iteration for the SQDOpt on quantum hardware and classically simulated VQE with the 20-qubit $�H_{12}$ molecule. These findings suggest that the proposed SQDOpt framework offers a scalable and robust pathway for quantum chemistry simulations on noisy intermediate-scale quantum (NISQ) devices.

A magnetic dipolar system is investigated, influenced by the $�z$-component of Zeeman splitting, Dzyaloshinsky–Moriya (DM) interaction, and Kaplan–Shekhtman–Entin-Wohlman–Aharony (KSEA) exchange interaction, with emphasis on the role of quantum resources in both closed and open settings. By analyzing the Gibbs thermal state and solving the Lindblad master equation, the behavior of quantum coherence, discord, and entanglement is studied under thermal equilibrium and dephasing noise. After exploring these resources, the model is applied to a closed quantum battery (QB). These results show that while Zeeman splitting degrades quantum resources in noisy and thermal regimes, it enhances QB performance by improving ergotropy, anti-ergotropy, storage capacity, and coherence during cyclic charging. The axial parameter further amplifies performance, leading to coherence saturation and persistent ergotropy growth, in line with the notion of incoherent ergotropy. KSEA interaction and the rhombic term consistently preserve coherence and entanglement under noise, thereby strengthening QB functionality. DM interaction mitigates thermal degradation of resources in the Gibbs state and improves performance, though its effect is limited under Pauli-$�X$ dephasing. Diverse behaviors are revealed, including increased ergotropy without coherence and the coexistence of coherence with zero extractable work. Finally, the nuclear magnetic resonance (NMR) is proposed as a feasible platform for experimental implementation.

In article number 2500069, Yong-Hoon Cho, Sven Höfling, Andreas T. Pfenning, and co-workers explore single photons in the telecom C-band emitted from a quantum dot embedded in a circular Bragg grating (bottom).

These photons interfere at a beam splitter (left) via the Hong-Ou-Mandel effect, revealing their indistinguishability.