Quantum Technologies Research Articles

Quantum Computing as a Catalyst for Microgrid Management: Enhancing Decentralized Energy Systems Through Innovative Computational Techniques

This paper introduces a groundbreaking framework for optimizing microgrid operations using the Quantum Approximate Optimization Algorithm (QAOA). The increasing integration of decentralized energy systems, characterized by their reliance on renewable energy sources, presents unique challenges, including the stochastic nature of energy supply-and-demand management. Our study leverages quantum computing to enhance the operational efficiency and resilience of microgrids, transcending the limitations of traditional computational methods. The proposed QAOA-based model formulates the microgrid scheduling problem as a Quadratic Unconstrained Binary Optimization (QUBO) problem, suitable for quantum computation. This approach not only accommodates complex operational constraints—such as energy conservation, peak load management, and cost efficiency—but also dynamically adapts to the variability inherent in renewable energy sources. By encoding these constraints into a quantum-friendly Hamiltonian, QAOA facilitates a parallel exploration of multiple potential solutions, enhancing the probability of reaching an optimal solution within a feasible time frame. We validate our model through a comprehensive simulation using real-world data from a microgrid equipped with photovoltaic systems, wind turbines, and energy storage units. The results demonstrate that QAOA outperforms conventional optimization techniques in terms of cost reduction, energy efficiency, and system reliability. Furthermore, our study explores the scalability of quantum algorithms in energy systems, providing insights into their potential to handle larger, more complex grid architectures as quantum technology advances. This research not only underscores the viability of quantum algorithms in real-world applications but also sets a precedent for future studies on the integration of quantum computing into energy management systems, paving the way for more sustainable, efficient, and resilient energy infrastructures.

Bipartite entanglement and Gaussian quantum steering in a whispering gallery mode coupled with two magnon modes

We theoretically propose a scheme to generate and control continuous variable bipartite entanglement and Gaussian quantum steering in an optical whispering gallery mode (WGM)-based cavity optomagnonical system that consists of two macroscopic YIG resonator. Owing to the well-known Faraday effect, both the magnon modes are coupled to single-mode optical WGM through nonlinear interaction. We investigate in detail the impact of several physical parameters such as effective cavity detuning, input laser power, environment temperature, optomagnonical coupling strengths and magnon decay rate on different bipartite entanglement. We also found a suitable parameter regime to obtain maximum cavity-magnon and magnon-magnon bipartite entanglement in our proposed system. It is interesting to note that the numerical simulation result shows that magnon-magnon entanglement persists up to 60K. With a proper choice of optomagnonical coupling strengths and normalized effective cavity detuning, we can effectively control the nature and strength of Gaussian quantum steering. In the WGM-based cavity optomagnonical system, our current work will offer a new way of greatly controlling a variety of nonclassical quantum correlations of macroscopic objects, which may find use in a number of contemporary quantum technology fields.

How to use the dispersion in the χ(3) tensor for broadband generation of polarization-entangled photons

Polarization-entangled photon pairs are a widely used resource in quantum optics and technologies and are often produced using a nonlinear process. Most sources based on spontaneous parametric down-conversion have relatively narrow optical bandwidths because the pump, signal, and idler frequencies must satisfy a phase-matching condition. Extending the bandwidth—for example, to achieve spectral multiplexing—requires changing some experimental parameters such as temperature, crystal angle, poling period, etc. Here we demonstrate broadband (tens of THz for each photon) generation of polarization-entangled photon pairs by spontaneous four-wave mixing in a diamond crystal, with a simple colinear geometry requiring no further optical engineering. Our approach leverages the quantum interference between electronic and vibrational contributions to the χ(3) tensor. Entanglement is characterized by a single realization of a Bell test over the entire bandwidth using fiber dispersion spectroscopy and fast single-photon detectors. The results agree with the biphoton wave function predicted from the knowledge of the χ(3) and Raman tensors and demonstrate the general applicability of our approach to other crystalline materials. Published by the American Physical Society 2025

High kinetic inductance cavity arrays for compact band engineering and topology-based disorder meters

Superconducting microwave metamaterials offer enormous potential for quantum optics and information science, enabling the development of advanced quantum technologies for sensing and amplification. In the context of circuit quantum electrodynamics, such metamaterials can be implemented as coupled cavity arrays (CCAs). In the continuous effort to miniaturize quantum devices for increasing scalability, minimizing the footprint of CCAs while preserving low disorder becomes paramount. In this work, we present a compact CCA architecture using superconducting NbN thin films manifesting high kinetic inductance. The latter enables high-impedance CCA (~1.5 kΩ), while reducing the resonator footprint. We demonstrate its versatility and scalability by engineering one-dimensional CCAs with up to 100 resonators and with structures that exhibit multiple bandgaps. Additionally, we quantitatively investigate disorder in the CCAs using symmetry-protected topological SSH edge modes, from which we extract a resonator frequency scattering of 0.22−0.03+0.04%. Our platform opens up exciting prospects for analog quantum simulations of many-body physics with ultrastrongly coupled emitters.

Coherent photoelectrical readout of single spins in silicon carbide at room temperature

Establishing a robust and integratable quantum system capable of sensitive qubit readout at ambient conditions is a key challenge for developing prevalent quantum technologies, including quantum networks and quantum sensing. Paramagnetic colour centres in wide bandgap semiconductors provide optical single-spin detection, yet realising efficient electrical readout technology in scalable material will unchain developing integrated ambient quantum electronics. Here, we demonstrate photoelectrical detection of single spins in silicon carbide, a material amenable to large-scale processing and electronic integration. With efficient photocarrier collection, we achieve a 1.7–2 times better signal-to-noise ratio for single spins of silicon vacancies with electrical detection than with optical detection suffering from saturating fluorescence and internal reflection. Based on our photoionisation dynamics study, further improvement would be expected with enhanced ionisation. We also observe single-defect-like features in the photocurrent image where photoluminescence is absent in the spectrum range of silicon vacancies. The efficient electrical readout in the mature material platform holds promise for developing integrated quantum devices.

The coherent measurement cost of coherence distillation

Quantum coherence—an indispensable resource for quantum technologies—is known to be distillable from a noisy form using operations that cannot create it. However, distillation exacts a hidden coherent measurement cost, which has not previously been examined. We devise the target effect construction to characterize this cost through detailed conditions on the coherence-measuring structure necessary in any process realizing exact (maximal or non-maximal) or approximate distillation. As a corollary, we lower-bound the requisite measurement coherence, as quantified by operationally-relevant measures. We then consider the asymptotic limit of distilling from many copies of a given noisy coherent state, where we offer rigorous arguments to support the conjecture that the (necessary and sufficient) coherent measurement cost scales extensively in the number of copies. We also show that this cost is no smaller than the coherence of measurements saturating the scaling law in the generalized quantum Stein's lemma. Our results and conjectures apply to any task whereof coherence distillation is an incidental outcome (e.g., incoherent randomness extraction). But if pure coherence is the only desired outcome, our conjectures would have the cautionary implication that the measurement cost is often higher than the distilled yield, in which case coherence should rather be prepared afresh than distilled from a noisy input.

Voltage detected single spin dynamics in diamond at ambient conditions

Defect centres in crystals like diamond or silicon find a wide application in quantum technology, where the detection and control of their quantum states is crucial for their implementation as quantum sensors and qubits. The quantum information is usually encoded in the spin state of these defect centres, but they also often possess a charge which is typically not utilized. We report here the detection of elementary charges bound to single nitrogen-vacancy (NV) centres several nanometres below the diamond surface using Kelvin Probe Force Microscopy (KPFM) under laser illumination. Moreover, the measured signal depends on the NV’s electron spin state, thus allowing to perform a non-optical single spin readout, a technique we refer to as “Surface Voltage Detected Magnetic Resonance” (SVDMR). Our method opens a way of coherent spin dynamics detection for quantum sensing applications and could be potentially applied to other solid state systems. We believe that this voltage-based readout would help to simplify the design of devices for quantum technology.

Microwave-based continuous variable quantum teleportation in open air

Abstract Quantum teleportation has achieved significant progress in the optical frequency domain but faces persistent challenges, including high transmission losses and limited transmittance. In contrast, the microwave frequency domain offers distinct advantages, such as reduced absorption losses, lower energy consumption, and compatibility with superconducting quantum technologies. To overcome the limitations of optical quantum teleportation, this study presents a microwave-based continuous-variable quantum teleportation (CVQT) scheme designed for open-air environments at room temperature. The proposed approach employs microwave two-mode squeezed states, with entanglement enhanced through quantum scissors operations to mitigate environmental degradation. Numerical simulations demonstrate that the maximum transmission distance of microwave entangled states for CVQT is about 200 m at room temperature. The results also indicate that the microwave CVQT scheme achieves lower attenuation and higher fidelity over short distances compared to optical frequency CVQT under similar weather conditions. Moreover, microwave quantum states exhibit reduced sensitivity to weather-induced variations, highlighting their robustness and practicality for open-air quantum communication applications.

Defect Engineering in Hexagonal Boron Nitride: Optical Properties of Stable Defect Complexes Arising from Boron Interstitials.

Hexagonal boron nitride (hBN) is a wide-band-gap semiconductor that is promising as a host material for solid-state quantum technologies through defect engineering. It has been shown that boron atoms can be removed from the lattice upon irradiation by electrons or light ions, creating boron vacancies and boron interstitials. While the optical properties of boron-vacancy-derived defects have been studied extensively, little is known about the optical properties of boron-interstitial-derived defects. In this work, we use state-of-the-art first-principles calculations to predict the electronic and optical properties of boron interstitials (Bint) and defect complexes comprising Bint and substitutional carbon impurities at boron and nitrogen sites (CB and CN). These carbon impurities can be present in as-grown hBN and can also be introduced intentionally. We demonstrate that these complexes are expected to be stable at room temperature. Our GW-Bethe-Salpeter equation (BSE) calculations show that Bint-CB and Bint-CN have low-energy optical transitions that are isolated in energy, making them suitable as single-photon emitters. Together with constrained density functional theory calculations to capture the red shift due to emission, we predict that Bint-CB and Bint-CN have zero phonon lines at ∼2.0 eV and ∼2.6 eV, respectively. Defects involving Bint are likely to be the source of blue emitters recently observed in regions several microns away from ion-irradiated parts of hBN. Our work sheds light on these recent experiments and introduces a fresh perspective to the field of quantum emitters in hBN─we show that defects related to Bint are potential single-photon emitters that can be intentionally created in hBN.

Acceleration-driven dynamics of Josephson vortices in coplanar superfluid rings

Precise control of topologically protected excitations, such as quantum vortices in atomtronic circuits, opens new possibilities for future quantum technologies. We theoretically investigate the dynamics of Josephson vortices (rotational fluxons) induced by coupled persistent currents in a system of coplanar double-ring atomic Bose-Einstein condensates. We study the Josephson effect in an atomic Josephson junction formed by coaxial ring-shaped condensates. Tunneling superflows, initiated by an imbalance in atomic populations between the rings, are significantly influenced by the persistent currents in the inner and outer rings. This results in pronounced Josephson oscillations in the population imbalance for both corotating and nonrotating states. If a linear acceleration is applied to the system, our analysis reveals peculiar azimuthal tunneling patterns and dynamics of Josephson vortices which leads to nonzero net tunneling current and shows sensitivity to the acceleration magnitude. When multiple Josephson vortices are present, asymmetric vortex displacements that correlate with both the magnitude and direction of acceleration can be measured, offering the potential for quantum sensing applications. Published by the American Physical Society 2025

An Energy Efficient Memory Cell for Quantum and Neuromorphic Computing at Low Temperatures.

Efficient computing in cryogenic environments, including classical von Neumann, quantum, and neuromorphic systems, is poised to transform big data processing. The quest for high-density, energy-efficient memories continues, with cryogenic memory solutions still unclear. We present a Cryogenic Capacitorless Random Access Memory (C2RAM) cell using advanced Si technology, which enhances storage density through its scalability and multistate capability. Remarkably, the C2RAM maintains data for over a decade with its extended retention times and offers potential as an artificial synapse. This positions C2RAM as an ideal nonvolatile memory candidate for cryogenic computing applications and emerging quantum technologies.

Coherent Phenomena in Exciton-Polariton Systems

Abstract Exciton-polariton systems, formed through the strong coupling of excitons and photons, provide a unique platform for investigating quantum coherence and collective dynamics in solid-state systems. These hybrid quasiparticles combine photonic and excitonic characteristics, enabling phenomena such as Rabi oscillations, long-distance coherent energy transfer, ballistic energy transport, and Bose-Einstein condensation. Their ability to sustain macroscopic quantum coherence, alongside their sensitivity to environmental and system-engineering factors, highlights their potential for advancing both fundamental quantum science and practical applications, including nanophotonics, energy harvesting, and quantum technologies. This review aims to offer a comprehensive exploration of coherent phenomena in exciton-polariton systems, spanning theoretical foundations, experimental realizations, and applications. Key topics include the dynamics of strong light-matter coupling, the role of vibrational modes and energetic disorder, and the interplay between coherence and dissipation. Advances in ultrafast spectroscopy and quantum electrodynamics models have been pivotal in uncovering polaritonic behaviour and optimizing system performance. Despite significant progress, challenges remain in maintaining coherence and addressing the effects of dissipation and disorder. By overcoming these hurdles, exciton-polariton systems promise transformative technological applications and deeper insights into quantum phenomena, positioning them as a cornerstone in the future of quantum science and technology.

Reconfigurable Three‐Dimensional Superconducting Nanoarchitectures

AbstractWhen materials are patterned in 3D, there exist opportunities to tailor and create functionalities associated with an increase in complexity, the breaking of symmetries, and the introduction of curvature and non‐trivial topologies. For superconducting nanostructures, the extension to the third dimension triggers the emergence of new physical phenomena, and lead to advances in technologies. Here, 3D nanopatterning is harnessed to fabricate and control the emergent properties of a 3D superconducting nanostructure. Not only are the existence and motion of superconducting vortices demonstrated in 3D but, with numerical simulations, it is shown that the confinement leads to well‐defined bending of the vortices within the volume of the structure. This 3D confinement manifests experimentally in a strong geometrical anisotropy of the critical field, through which the reconfigurable coexistence of superconducting and normal states in the 3D superconducting architecture, and the local definition of weak links, are achieved. In this way, an intermediate regime of nanosuperconductivity is uncovered, where the vortex state is truly 3D and can be designed and manipulated by geometrical confinement. This insight into the influence of 3D geometries on superconducting properties offers a route to local reconfigurable control for future computing devices, sensors, and quantum technologies.

AI-Enhanced Simulation of Superalgebra-Based Topological Quantum Computation

This paper presents a novel framework that integrates artificial intelligence with superalgebraic structures to simulate topological quantum computation (TQC) in systems governed by Lie superalgebras such as osp(1∣2) and sl(2∣1). By combining symbolic algebra, modular tensor category theory, and generative AI models—including variational autoencoders and diffusion models—the proposed system enables accurate, scalable simulation of non-Abelian anyonic braiding and fusion operations within graded symmetry constraints. The framework encodes superalgebraic invariants and topological rules into neural architectures, allowing physically valid and symmetry-preserving generation of braid paths and fusion outcomes. Experimental results demonstrate high fidelity, topological consistency, and robustness against noise, with successful emulation on quantum hardware platforms such as IBM Q and IonQ. This research opens new avenues for fault-tolerant, algebraically informed quantum simulation, circuit synthesis, and adaptive control in next-generation quantum technologies. Keywords: topological quantum computation, superalgebra, Lie superalgebras, modular tensor categories, osp(1∣2), sl(2∣1), anyons, braiding, fusion rules, symbolic AI, generative models, quantum simulation, quantum invariants, diffusion models, fault-tolerant quantum computing

Control of Solid-State Nuclear Spin Qubits Using an Electron Spin- 1/2

Solid-state quantum registers consisting of optically active electron spins with nearby nuclear spins are promising building blocks for future quantum technologies. For electron spin-1 registers, dynamical decoupling (DD) quantum gates have been developed that enable the precise control of multiple nuclear spin qubits. However, for the important class of electron spin-1/2 systems, this control method suffers from intrinsic selectivity limitations, resulting in reduced nuclear spin gate fidelities. Here, we demonstrate improved control of single nuclear spins by an electron spin-1/2 using dynamically decoupled radio-frequency (DDRF) gates. We make use of the electron spin-1/2 of a diamond tin-vacancy center, showing high-fidelity single-qubit gates, single-shot readout, and spin coherence beyond a millisecond. The DD control is used as a benchmark to observe and control a single 31C nuclear spin. Using the DDRF control method, we demonstrate improved control on that spin. In addition, we find and control an additional nuclear spin that is insensitive to the DD control method. Using these DDRF gates, we show entanglement between the electron and the nuclear spin with 72(3)% state fidelity. Our extensive simulations indicate that DDRF gate fidelities well in excess are feasible. Finally, we employ time-resolved photon detection during readout to quantify the hyperfine coupling for the electron’s optically excited state. Our work provides key insights into the challenges and opportunities for nuclear spin control in electron spin-1/2 systems, opening the door to multiqubit experiments on these promising qubit platforms. Published by the American Physical Society 2025

Improved Electron-Nuclear Quantum Gates for Spin Sensing and Control

The ability to sense and control nuclear spins near solid-state defects might enable a range of quantum technologies. Dynamically decoupled radio-frequency (DDrf) control offers a high degree of design flexibility and long electron-spin coherence times. However, previous studies have considered simplified models and little is known about optimal gate design and fundamental limits. Here, we develop a generalized DDrf framework that has important implications for spin sensing and control. Our analytical model, which we corroborate by experiments on a single NV center in diamond, reveals the mechanisms that govern the selectivity of gates and their effective Rabi frequencies, and enables flexible detuned gate designs. We apply these insights to numerically show a 60× sensitivity enhancement for detecting weakly coupled spins and study the optimization of quantum gates in multiqubit registers. These results advance the understanding for a broad class of gates and provide a toolbox for application-specific design, enabling improved quantum control and sensing. Published by the American Physical Society 2025

Progress in integrated and fiber optics for time-bin based quantum information processing

The development of integrated photonic systems, both on-chip and fiber-based, has transformed quantum photonics by replacing bulky, fragile free-space optical setups with compact, efficient, and robust circuits. Photonic platforms incorporating fiber-connected sources of correlated and entangled photon pairs offer practical advantages, such as operation at room temperature, efficient integration with telecom infrastructure, and compatibility with mature and efficient semiconductor fabrication processes for cost-effective and large-scale optical circuits. The stability and scalability of integrated quantum photonics platforms have facilitated the generation and processing of quantum information in the temporal domain within a single spatial mode. Time-bin encoded states, known for their robustness against decoherence and compatibility with existing fiber-optic infrastructure, have shown to be an efficient paradigm for advanced applications like quantum secure communication, information processing, spectroscopy, imaging, and sensing. This review examines recent advancements in fiber- and chip-based platforms for generating non-classical states and their applications as quantum state processors in the time domain. We discuss the generation of pulsed quantum frequency combs using microring resonators and intra-cavity mode-locked laser schemes, enabling co- and cross-polarized quantum photonic states. Additionally, the versatility of these resonator chips for entanglement generation is emphasized, including two- and multi-photon time-bin entangled schemes. We highlight the development of time-bin entanglement analyzers in fiber architectures, featuring ultrahigh stability and post-selection-free capabilities, which enable precise and efficient characterization of two- and higher-dimensional time-bin entanglement. We also review scalable on-chip schemes for quantum key distribution, demonstrating low quantum bit error rates and compatibility with higher-dimensional quantum communication protocols. Further, methods for enhancing temporal resolution in detection schemes, crucial for time-bin encoding, are presented, such as the time-stretch sampling technique using electro-optic modulation. These innovations, relying on readily available, telecom-based fiber-optic components, provide practical, scalable, and cost-effective solutions for advancing quantum photonic technologies. Looking forward, time-bin encoding is expected to play a pivotal role in the advancement of quantum repeaters, distributed quantum networks, and hybrid light-matter systems, advancing the realization of globally scalable quantum technologies.

Single electron quantum dot in two-dimensional transition metal dichalcogenides

Spin-valley properties in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) has attracted significant interest due to the possible applications in quantum computing. Spin-valley properties can be exploited in TMDC quantum dot (QD) with well-resolved energy levels. This requires smaller QDs, especially in material systems with heavy carrier effective mass e.g. TMDCs and silicon. Device architectures employed for TMDC QDs so far have difficulty achieving smaller QDs. Therefore, an alternative approach in the device architecture is needed. Here, we propose a multilayer device architecture to achieve a gate-defined QD in TMDC with a relatively large energy splitting on the QD. We provide a range of device dimensions and dielectric thicknesses and its correlation with the QD energy splitting. The device architecture is modeled realistically. Moreover, we show that all the device parameters used in modeling are experimentally achievable. These studies lay the foundation for future work toward spin-valley qubits in TMDCs. The successful implementation of these device architectures will drive the technological development of 2D materials-based quantum technologies.

Quantum-Enhanced AI and Machine Learning: Transforming Predictive Analytics

Background: Artificial Intelligence (AI) and Machine Learning (ML) have significantly transformed predictive analytics across domains such as healthcare, finance, and environmental sciences. However, traditional ML models face limitations when dealing with large-scale, high-dimensional datasets, particularly due to computational inefficiencies and the "curse of dimensionality." Quantum computing offers promising solutions by leveraging superposition and entanglement to perform complex computations at exponential speeds. Objective: This study aims to explore how quantum computing can enhance AI and ML models, particularly in the domain of predictive analytics. It proposes a comprehensive Quantum-AI framework that integrates quantum technologies into existing predictive systems to overcome the challenges posed by classical approaches. Methods: The study employed hybrid quantum-classical models using frameworks like Qiskit, TensorFlow Quantum, and Pennylane. Datasets were sourced from real-world applications in finance, healthcare, and climate science. Experiments were designed to compare classical and quantum- enhanced models on metrics such as accuracy, scalability, and computational time. Specific algorithms used include Quantum Support Vector Machines (QSVM) and Quantum Neural Networks (QNN). Result: The proposed quantum-enhanced models showed significant improvements: • Accuracy increased from 85% (classical) to 92% (quantum) in finance-related predictions. • Diagnostic models in healthcare achieved a 94% accuracy rate and reduced training time by 50%. • Climate modeling tasks achieved 90% improved accuracy and 20% faster simulation times. The results validate the effectiveness of quantum models in processing large, complex datasets more efficiently. Conclusion: Quantum-enhanced AI presents a transformative approach to predictive analytics by addressing the core limitations of classical ML systems. This study demonstrates the practical feasibility and industrial relevance of integrating quantum computing into AI workflows. It opens avenues for further research in developing scalable, domain-specific quantum algorithms and hybrid AI models for real-world applications.

Steady-state coherence in multipartite quantum systems: its connection with thermodynamic quantities and impact on quantum thermal machines

Abstract Understanding how coherence of quantum systems affects thermodynamic quantities, such as work and heat, is essential for harnessing quantumness effectively in thermal quantum technologies. Here, we study the unique contributions of quantum coherence among different subsystems of a multipartite system, specifically in non-equilibrium steady states, to work and heat currents. Our system comprises two coupled ensembles, each consisting of N particles, interacting with two baths of different temperatures, respectively. The particles in an ensemble interact with their bath either simultaneously or sequentially, leading to non-local dissipation and enabling the decomposition of work and heat currents into local and non-local components. We find that the non-local heat current, as well as both the local and non-local work currents, are linked to the system quantum coherence. We provide explicit expressions of coherence-related quantities that determine the work currents under various intrasystem interactions. Our scheme is versatile, capable of functioning as a refrigerator, an engine, and an accelerator, with its performance being highly sensitive to the configuration settings. These findings establish a connection between thermodynamic quantities and quantum coherence, supplying valuable insights for the design of quantum thermal machines.