Photocatalytic materials form an important class of quantum materials in which the electronic structure governs charge-carrier behaviour and reaction pathways through quantum-mechanical processes. To accelerate the discovery of superior photocatalytic quantum materials, we present a quantum-enhanced machine learning framework that integrates many-body electronic-structure descriptors with ensemble machine-learning algorithms. The framework explicitly incorporates quantum coherence lengths, electron–phonon coupling strengths, exciton binding energies, and spin–orbit coupling parameters obtained from density functional theory (DFT) and many-body perturbation theory GW approximation and the Bethe–Salpeter equation (GW-BSE) calculations. The database is based on a screened library of 8642 photocatalytic materials that have been experimentally characterised in H $ _2$ evolution reactions and contains 152 descriptors relating to electronic correlations, quantum confinement effects, and spin-dependent properties. Five-fold cross-validation yields $R^2 = 0.82$ and MAE $ = 0.28$ log units, $n$ 18% relative improvement in prediction accuracy ( $R^2$ : 0.82 vs 0.69) over a baseline model using only classical descriptors ( $R^2 = 0.69$ , MAE $ = 0.38$ log units). High-throughput screening of 45 000 hypothetical compositions yielded 214 candidate quantum materials; DFT and GW-BSE validation on representative subset of 23 of these candidates showed 72% agreement within quantum uncertainty bounds. quantum coherence shows a statistically significant association with photocatalytic charge separation, with optimal coherence lengths of 15–35 nm being strongly correlated with increased hydrogen-evolution production. Our findings indicate that many-body interactions, including exciton dissociation dynamics and quantum tunnelling contributions to interfacial charge transfer, are predictive of photocatalytic activity in emerging quantum materials.
Gallium nitride (GaN) quantum emitters (QEs) have rapidly emerged as a promising platform for room-temperature single-photon generation, benefiting from high emission rates, robust optical properties, and compatibility with industrial GaN epitaxy and device fabrication. Over the past decade, these emitters have demonstrated bright, linearly polarized emission, strong antibunching without tight spectral filtering, and in some cases microwave and magnetically addressable spin transitions, highlighting their potential for quantum communication, sensing, and integrated photonics. In this Perspective, we consolidate recent progress in understanding the formation, control, and photophysical behaviour of GaN QEs, including advances in controlled epitaxy, activation techniques, and external-field tuning. We further discuss outstanding questions surrounding their microscopic origin and spectral variability, and identify key challenges related to spectral stability, spin coherence, and device integration. Finally, we outline the most promising research directions and technological pathways that could enable scalable, low-cost, room-temperature quantum light sources based on GaN.
Deterministic light sources capable of generating quantum states on-demand at wavelengths compatible with fiber optics and atmospheric transmission windows are essential for practical applications in quantum communication, distributed photonic quantum computing, and quantum metrology. Currently, the technology providing semiconductor quantum emitters with the most promising properties is based on filling droplet-etched nanoholes to form quantum dots (QDs). However, the standard GaAs/AlGaAs material system does not offer telecom window emission. Here, we combine this growth method with antimonide-based materials to demonstrate single-photon emission at 1500 nm from a droplet-etched InGaSb QD. Our device with an antimony-based high refractive index contrast back-reflector designed for cryogenic operation and a solid immersion lens improves photon extraction. QD states are protected by a potential barrier limiting the influx of surrounding carriers, which however prevents revealing excitonic fine structure under nonresonant excitation. In this work, we employ a frequency-tunable continuous wave laser to achieve longitudinal optical (LO) phonon-assisted excitation of the QD ground state and resonant excitation of an excited state. These direct approaches for exciting a single InGaSb QD unlock access to its excitonic fine structure. The typical neutral biexciton-exciton cascade exhibits a negative binding energy of 1.4 meV (2.6 nm) and a fine structure splitting of 24.1 +/- 0.4 & micro;eV. Furthermore, we obtain spectrally isolated emission from a charged exciton with a multi-photon probability of 5% with LO phonon-assisted two-color excitation. These results represent a major step towards using this novel antimonide-based QD emitters as deterministic quantum light sources in complex quantum secure networks exploiting the wavelength compatibility with standard telecom fibers.
Chiral phonons (CPs)—vibrational modes carrying angular momentum—offer a new degree of freedom for phononic quantum information and topological energy transport. However, their microscopic identification and control within van der Waals materials remain limited. Here, we report the direct observation of domain-dependent CP junctions in layered ferroelastic WO₂I₂, whose intrinsic micro-strain twinning provides a natural platform for CP localization. Using helicity-resolved and angle-resolved Raman spectroscopy, we reveal distinct circular polarization responses in specific domains, where A g modes at 115 cm −1 and 753 cm −1 exhibit strong helicity contrast, while the B g mode remains helicity-independent. These chiral responses are confined to ferroelastic domains with higher local strain. Density functional theory (DFT + U ) calculations accurately reproduce the experimental Raman features and show that strain induces degeneracy lifting in the A g modes, consistent with domain-resolved observations. Our results demonstrate that ferroelastic strain engineering can be used to generate and manipulate microscopic CP junctions, establishing WO₂I₂ as a promising candidate for strain-tunable quantum phononic devices.
Negatively charged germanium vacancy centers (GeV) in diamond are a promising platform for quantum computing and quantum communication. However, these applications require the precise incorporation of GeV centers with good optical properties inside of nanophotonic structures. In this work, we demonstrate the highly efficient local creation of GeV centers in diamond via focused-ion-beam implantation, followed by high-temperature annealing. We report the successful creation of GeV centers over the depth range of 5.5 - 30 nm. Implantation at low fluence enables the creation of single GeV centers. The formation yield strongly depends on implantation energy and fluence, reaching up to 33
