Color symmetry breaking in a nonlinear optical microcavity
Luca O. Trinchão,
Alekhya Ghosh,
Arghadeep Pal,
Haochen Yan,
Toby Bi,
Shuangyou Zhang,
Nathalia B. Tomazio,
Flore K. Kunst,
Lewis Hill, et al.
Laser & Photonics Reviews
e71644
(2026)
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Spontaneous symmetry breaking leads to diverse phenomena across the natural sciences, from the Higgs mechanism in particle physics to superconductors and collective animal behavior. In photonic systems, the symmetry of light states can be broken when two optical fields interact through the Kerr nonlinearity, as shown in early demonstrations with counterpropagating and cross-polarized modes. Here, we report the first observation of color symmetry breaking in an integrated silicon nitride microring, where spontaneous power imbalance arises between optical mode at different wavelengths, mediated by the Kerr effect. The threshold power for this effect is as low as 19 mW. By examining the system's homogeneous states, we further demonstrate a Kerr-based nonlinear activation-function generator that produces sigmoid-, quadratic-, and leaky-ReLU-like responses. These findings reveal previously unexplored nonlinear dynamics in dual-pumped Kerr resonators and establish new pathways toward compact, all-optical neuromorphic circuits.
Generating quantum entanglement from sunlight
Cheng Li,
Jasvinder Brar,
Michael Küblböck,
Jeremy Upham,
Hanieh Fattahi,
Robert W. Boyd
Energy consumption is on track to become a serious bottleneck in integrating quantum technologies with existing information and communication infrastructure. In photonic quantum technologies, a considerable portion of the energy overhead stems from the use of lasers, whose high coherence has long been considered indispensable for preparing quantum states of light. Here, we demonstrate that despite their low optical coherence, natural sources of light, such as sunlight, can produce quantum-entangled photon states by means of nonlinear optical effects. From spontaneous parametric down-conversion pumped by sunlight, we detect polarization-entangled photon pairs with a concurrence of C = 0.905 ± 0.053, a purity of P = 0.919 ± 0.045, and a fidelity to a Bell state of F = 0.939 ± 0.027. The resulting two-photon state violates Bell's inequality with S = 2.5408 ± 0.2171, which exceeds the threshold value of 2 to confirm quantum behavior. More importantly, we observe a photon pair generation rate of ~1600 s⁻¹ (mW of pump power)⁻¹, which is comparable to that of laser-pumped SPDC when normalized for the spectral bandwidth of the pump. Our work paves the way for developing sustainable and accessible photonic quantum technologies, especially for implementation in resource-constrained areas such as the Arctic region and satellites in space for interplanetary missions.
Certifying Non-Classicality and Non-Gaussianity Through Optical Parametric Amplification
Mahmoud Kalash,
M. H. M. Passos,
Éva Rácz,
László Ruppert,
Radim Filip,
Maria Chekhova
Non-Gaussian states of light are essential for numerous quantum information protocols; thus, certifying non-Gaussianity (NG) is crucial. Full quantum state tomography, commonly used for this purpose, is complicated and yields inconclusive results for strongly mixed states. Certifying NG through directly measurable parameters is a simpler alternative, typically achieved by measuring photon-number probabilities—either directly, using photon-number resolving detectors, or through Hanbury Brown-Twiss type measurements with single-photon detectors. Here, we demonstrate, theoretically and experimentally, that phase-sensitive optical parametric amplification (OPA), followed by conventional intensity detection, can effectively replace this approach. Our proposed witness relies on the mean photon number (relative to that produced by the amplifier without any input) and the second-order correlation function after OPA. Both can be directly obtained from the measured amplified intensity and are invariant to detection losses. The method therefore requires neither photon-number resolution nor high detection efficiency. In a proof-of-principle experiment, we successfully certify the quantum NG of a heralded quasi-single-photon state. Since OPA is a broadband and multimode process, our method provides a foundation for developing high-dimensional quantum technologies utilizing broadband multimode non-Gaussian states.
Bridging Frustration and Non-Hermiticity via COMPASS: An Adaptive Biorthogonal Neural Quantum State Framework
Lavoisier Wah,
Flore K. Kunst,
Mohamed Hibat-Allah
In this work, we introduce a complementary optimization method for progressive and adaptive state search (COMPASS) based on biorthogonal adaptive recurrent neural quantum states. Our approach combines an adaptive autoregressive architecture with a biorthogonal variational Monte Carlo scheme as well as a complementary optimization scheme that alternates between energy and variance minimization. This enables the stable convergence to ground-state eigenpairs, while avoiding Markov chain sampling through exact autoregressive generation. We demonstrate that for parity-time(PT)-symmetric Hamiltonians, unconstrained complex ansatze can spontaneously break PT symmetry during optimization, even in the unbroken phase, leading to spurious imaginary energies. Real-valued ansatze, on the other hand, naturally constrain the optimization to the correct physical manifold. Conversely, for generic non-Hermitian (NH) Hamiltonians without symmetry protection and complex spectra, complex ansatze are essential for capturing complex ground-state properties. Our results establish that physically-informed ansatz selection is crucial for reliable NH simulations. By combining adaptive architectures, biorthogonal optimization, and symmetry-aware modeling, this framework enables a direct study of 1D and 2D NH many-body systems without Hermitian embeddings or adiabatic continuation. Applying this framework to systems with frustrated magnetism, we show that gap frustration provides a quantitative shield against NH spectral instability, with the frustration gap setting a critical threshold for PT-symmetry breaking. Also, complexifying the frustration coupling itself generates a new topologically nontrivial network of diabolic level crossings, controlled by the phase of the complex coupling, that has no Hermitian analog. We term this novel spectral topology in NH frustrated systems the diabolic ring.
Agentic Exploration of Physics Models
Maximilian Nägele,
Florian Marquardt
Physical Review X
16
031002
(2026)
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The process of scientific discovery relies on an interplay of observations, analysis, and hypothesis generation. Machine learning is increasingly being adopted to address individual aspects of this process. However, it remains an open challenge to fully automate the heuristic, iterative loop required to discover the laws of an unknown system by exploring it through experiments and analysis, without tailoring the approach to the specifics of a given task. Here, we introduce sciexplorer, an agent that leverages large language model tool-use capabilities to enable exploration of systems without any domain-specific blueprints and apply it to physical systems that are initially unknown to the agent. We test sciexplorer on a broad set of models spanning mechanical dynamical systems, wave evolution, and quantum many-body physics. Despite using a minimal set of tools, primarily based on code execution, we observe impressive performance on tasks such as recovering equations of motion from observed dynamics and inferring Hamiltonians from expectation values. The demonstrated effectiveness of this setup opens the door toward similar scientific exploration in other domains, without the need for fine-tuning or task-specific instructions.
Spectral-topology-induced criticality in non-Hermitian fermionic metals
Quantum matter emerges from the interplay of fluctuations, topology, and entanglement, which - in equilibrium - governs quantized transport, universal criticality, and topological classification. Non-Hermitian systems, widely explored in platforms ranging from electric circuits to photonics, are intrinsically out-of-equilibrium, and display fundamentally new phenomena, including complex spectra, spectral winding, exceptional topology, and non-unitary dynamics. A central challenge is understanding how the complex single-particle spectrum governs universal many-body behavior. We introduce a symmetry-protected dynamical topological index derived directly from the complex spectrum. Through the lens of algebraic topology, more specifically Morse theory, we identify critical points in the spectrum with topological defects, whose curvature and stability are protected under continuous deformations. This links spectral geometry to many-body observables, unifying non-Hermitian band topology, entanglement, and transport. We demonstrate that non-Hermitian quantum criticality in non-interacting systems is controlled by gain-and-loss-selected non-equilibrium steady states, which dynamically generate an emergent imaginary Fermi surface whose Fermi points host scale-invariant gapless modes with logarithmic entanglement scaling and algebraic correlations. Our work establishes a unified framework for non-Hermitian quantum matter, connecting spectral topology to Morse theory, revealing a topological foundation of non-equilibrium quantum criticality.
Kerr-induced non-Gaussianity of a bright ultrafast quantum state
Andrei Rasputnyi,
Ilya Karuseichyk,
Gerd Leuchs,
Francesco Tani,
Denis Seletskiy,
Maria Chekhova
Characterizing macroscopic quantum states of light is a frontier challenge at the interface of quantum optics and high-intensity photonics. Here, we demonstrate the first, to our knowledge, direct phase-space tomography of a bright, ultrafast quantum state. We adapt a single-shot f-2f interferometer to sample the Husimi Q-function of a 25 fs bright squeezed vacuum (BSV) pulse (mean photon number N ~ 10^12) subject to Kerr nonlinearity. Our measurement reveals a clear transformation from a Gaussian distribution with pronounced quadrature antisqueezing to a characteristic "S"-shaped profile as the intensity-dependent nonlinear phase increases. Crucially, we show theoretically that despite optical loss, the state does not degrade into classically modulated light but is rigorously described as a statistical mixture of squeezed coherent states. While global Wigner negativity is masked by technical noise, our results show theoretically that the constituent states individually retain strong Wigner-negative features. This work bridges quantum optics and high-intensity photonics, establishing a platform for diagnosing bright quantum resources.
Nano-electronvolt Fourier-limited transition of a single surface-adsorbed molecule
Masoud Mirzaei,
Alexey Shkarin,
Burak Gurlek,
Johannes Zirkelbach,
Ashley J. Shin,
Irena Deperasińska,
Boleslaw Kozankiewicz,
Tobias Utikal,
Stephan Götzinger, et al.
High-resolution spectroscopy allows the probing of weak interactions and subtle phenomena. Although such measurements are routinely performed in the gas phase and in crystalline materials, studies of adsorbed species on surfaces have previously fallen short of the ultimate spectral resolution, where dephasing is eliminated and the transition linewidth is determined by the excited-state lifetime. In this work, we devise an approach to surface preparation and deposition that provides access to Fourier-limited electronic transitions in single molecules on the surface of an organic crystal. By performing spectroscopy and super-resolution microscopy at liquid helium temperature, we shed light on the spectral and spatial features of the adsorbed species. Our results pave the way for investigations in solid-state physics, where angstrom spatial resolution can be combined with high-resolution laser spectroscopy.
Removal of guided acoustic wave Brillouin scattering to the quantum-noise limit using symmetric interferometry in twisted photonic crystal fibers
Vishal Choudhury,
Kevin Jaksch,
Markus Lippl,
Gerd Leuchs,
Christoph Marquardt,
Nicolas Joly
Guided acoustic wave Brillouin scattering (GAWBS) is a major obstacle in fiber-based quantum and high-speed classical communication systems as well as in interferometry. The transverse phonons driving it modulate the light field in the fiber core, adding thermal noise to the signal. To this day, there is no known method to eliminate GAWBS from the fiber or to compensate its effects completely. In this letter, we present twisted photonic crystal fibers (t-PCF) as the first-ever fiber system allowing a complete removal of mixed torsional radial GAWBS in a Stokes basis. The torsional radial modes modulate the fiber asymmetrically in the transverse direction, resulting in linear birefringence. While pure phase modulation is added as common noise in the guided fiber modes and can be easily removed through self-referencing, linear birefringence induces polarization modulation, which cannot be counteracted. In t-PCFs, the transverse symmetry of the geometry translates to multiple symmetries in the acoustic and optical domains in the circular basis. This enables equal phase accumulation in certain orientations in the two optical modes. Through experiments and theory, we show that the GAWBS-induced phase can be compensated down to the quantum-noise limit by self-referencing in a symmetric interferometer with Stokes detection.
Uncovering Latent Structures in Robust Pulse Sequences: A Model-Based Reinforcement Learning Approach for Adaptable Quantum Control
Tobias Kiermeyer,
Thomas Heydenreich,
Léo Van Damme,
Sebastian Hohenemser,
Florian Marquardt,
Steffen J. Glaser
Real-time adaptive control of quantum systems requires rapid generation of robust, high-fidelity pulses across a continuous range of operating conditions. Standard optimization algorithms such as gradient-ascent pulse engineering (GRAPE) solve each instance independently, discarding information between runs and requiring costly reinitialization when parameters change. We present an approach to robust optimal quantum control based on model-based reinforcement learning, in which a single neural network -- embedding the Hamiltonian directly into the training pipeline -- generates robust gates across an entire family of gate configurations, without pre-computed training data. Demonstrated on a single-spin (two-level) system, the trained networks produce pulses for arbitrary rotation angles over a range of pulse durations, detunings, and field inhomogeneities in milliseconds, at fidelities comparable to multi-seed GRAPE. The framework is inherently adaptable: any parameter entering the Hamiltonian can serve as a network input, extending the approach to different systems and control settings. Beyond speed, the network reveals structure in the control landscape: it discovers the same structured phase profiles that appear in GRAPE solutions -- made identifiable through fidelity-invariant symmetry transformations -- but more consistently than independent optimization. This consistency enables smooth interpolation across the entire trained parameter space.
Large-Language-Model Discovery of Quantum LDPC Codes through Structured Concept Evolution
Quantum computers could outperform classical machines on important problems, but only if the errors that pervade quantum hardware can be corrected at scale. Quantum low-density parity-check (qLDPC) codes offer a promising route to this goal by combining sparse parity checks with finite encoding rate and growing distance, but their construction remains a challenging discrete design problem. Here we introduce structured concept evolution (SCE), a search framework that pairs a large language model with a structured algebraic mutation grammar to discover lifted-product code families, a class of CSS qLDPC codes. Instead of asking the LLM to design codes from first principles, SCE evolves structured concepts consisting of algebraic specifications paired with executable programs that realize them, using hierarchical mutations that modify the group algebra, protograph geometry, or base space. Running SCE, we discover a diverse set of competitive code families, ranging from abelian constructions to families over non-abelian groups beyond those underlying standard designs such as bivariate-bicycle codes, and characterize them under code-capacity depolarizing noise with BP+OSD decoding. These results are obtained with lightweight models (GPT-5.4-mini and GPT-5.4-nano).
Automation and improvement of WBC mechanical profiling in deformability cytometry
Sara Kaliman,
Shada Abuhattum Hofemeier,
Benedikt Hartmann,
Jochen Guck
Biophysical Journal
125
(12)
3048-3059
(2026)
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Deformability cytometry (DC) is a powerful biophysical technique that enables cost-effective, high-throughput characterization of disease-associated changes in blood cell mechanics. Mechanical profiling of living white blood cells (WBCs) is particularly valuable due to their critical role in the immune response. However, reliably identifying and classifying WBC subtypes in a label-free manner remains a significant challenge. Until now, the analysis pipeline has relied on manual gating by trained experts, limiting scalability and reproducibility. In this study, we present a fully automated and generalizable framework for WBC classification in shear flow DC experiments, based on box filters and unsupervised clustering of cell populations. Both box filters and unsupervised clustering rely on cell shape features derived from high-accuracy segmentation and on cell texture features derived from bright-field images. This unsupervised approach not only improves reproducibility and reduces processing time but also overcomes key limitations of supervised models that require extensive training data and often suffer from reduced performance under varying imaging conditions. We validated our method by comparing cell features obtained through manual gating and automated classification across six experimental sets. These sets incorporated variations in blood donors, anticoagulants (EDTA and citrate), blood collection sources (capillary and venous), and device brightness settings. Each set included five repeated measurements. The results consistently confirmed the reliability and robustness of the method across all tested conditions and WBC types. Importantly, this automated pipeline enables the inclusion of WBCs with membrane protrusions—typically excluded from standard analyses—allowing for morphological characterization of potentially activated cells. Moreover, by using shape features derived from the original contour rather than the convex hull, we improve morphological accuracy and reduce measurement variability. This approach thus enhances the accuracy, consistency, and scalability of WBC mechanophenotyping and enables high-throughput analysis across large cohorts.
High-Throughput Mechanomic Screening Reveals Novel Regulators of Single-Cell Mechanics
Laura von Selzam,
Katarzyna Plak,
Christine Schweitzer,
Cornelia Liebers,
Paul Müller,
Marta Urbanska,
Martin Kräter,
Buzz Baum,
Jona Kayser, et al.
Biophysical Journal
125
(12)
3060-3073
(2026)
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The mechanical properties of cells are dynamic, allowing them to adjust to different needs in different biological contexts. In recent years, advanced biophysical techniques have enabled the rapid, high-throughput assessment of single-cell mechanics, providing new insights into the regulation of the mechanical cell phenotype. However, the molecular mechanisms by which cells maintain and regulate their mechanical properties remain poorly understood. Here, we present a genome-scale RNA interference (RNAi) screen investigating the roles of kinase and phosphatase genes in regulating single-cell mechanics using Real-Time Fluorescence and Deformability Cytometry (RT-FDC). Our screen identified 82 known and novel mechanical regulators across diverse cellular functions from 214 targeted genes, leveraging RT-FDC’s unique capabilities for comprehensive, high-throughput mechanical phenotyping with single-cell and cell cycle resolution. These findings refine our understanding of how signaling pathways coordinate structural determinants of cell mechanical phenotypes and provide a starting point for uncovering new molecular targets involved in biomechanical regulation across diverse biological systems.
Composable free-space continuous-variable quantum key distribution using discrete modulation
Kevin Jaksch,
Thomas Dirmeier,
Yannick Weiser,
Stefan Richter,
Oemer Bayraktar,
Bastian Hacker,
Conrad Rösler,
Imran Khan,
Stefan Petscharning, et al.
Science Advances
12
eadv1440
(2026)
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Continuous-variable (CV) quantum key distribution (QKD) allows for quantum secure communication with the benefit of being close to classical coherent communication. In recent years, CV QKD protocols using a discrete number of displaced coherent states have been studied intensively as the modulation can be directly implemented with real devices with finite resolution. Until now, experiments only calculated key rates in the asymptotic regime. Here, we present a CV QKD system using discrete modulation that is especially designed for atmospheric channels. We use polarization encoding to exploit the nonbirefringent nature of the turbulent atmosphere. This allows to expand CV QKD networks beyond the existing fiber backbone. In a laboratory demonstration with a static 3-decibel loss channel, we implemented a recently developed security proof allowing to calculate composable finite-size key rates against independently and identically distributed collective attacks. We applied the full QKD protocol including a quantum random number generator, error correction, and privacy amplification to extract secret keys.
Higher-order exceptional points in a multimode continuum optoacoustic system
Anton Montag,
Julius Gohsrich,
Quentin Levoy,
Birgit Stiller,
Flore K. Kunst
Exceptional points appear in non-Hermitian systems as degeneracies, where not only eigenvalues but also eigenvectors coalesce. They are of great theoretical and experimental interest due to their exotic topological properties and enhanced sensitivity to perturbations. Experimental realizations of higher-order exceptional points, where more than two eigenvectors coalesce, rely on highly fine-tuned setups. Recently, stimulated Brillouin scattering has been employed to generate second-order exceptional points in a fabrication-free setup by leveraging off-resonant scattering. In this work we generalize this approach, and we develop an off-resonant, multimode theory for stimulated Brillouin scattering as an avenue towards realizing symmetry-induced exceptional points of any order. We present the experimental implementation of our program in an accompanying paper. Our multimode theory could also be employed in applications in optoacoustic sensing, synthetic neuromorphic computing, microwave photonic filters, and optoacoustic quantum signal processing.
Multi-dimensional parameter space of higher-order exceptional points induced by Brillouin optoacoustics
Grigorii Slinkov,
Anton Montag,
Julius Gohsrich,
Quentin Levoy,
Paulina Fuentes Rivera,
Flore K. Kunst,
Birgit Stiller
Exceptional points (EPs) are degeneracies in the spectrum of non-Hermitian systems, where both the eigenvalues and eigenvectors coalesce. In the vicinity of an n-th order EP, the eigenvalues generally show n-th-root dependence on the system parameters, making EPs potentially promising candidates for ultra-sensitive measurements. Usually EPs are implemented in precisely fabricated nano- and microstructures. In this work, we instead show the experimental implementation of a third-order EP (EP3) using the synthetic dimension in a single-mode optical fiber, leveraging multi-frequency Brillouin scattering. We perform a multi-dimensional scan of the parameter space revealing not only an EP3 but also additional topological structures connected to it. Our work paves the way toward fabrication-free realizations of exceptional points of arbitrary order.
Parity-induced generalized Brillouin zone without non-Hermitian skin effect
Acute spectral sensitivity to boundary conditions and the formation of a generalized Brillouin zone associated with complex quasimomenta are features frequently attributed to systems with non-trivial non-Hermitian topology, showcasing the non-Hermitian skin effect. We show that, away from the thermodynamic limit, these features themselves are not uniquely tied to this phenomenon; they can similarly arise as parity-induced even-odd effects in non-Hermitian systems without skin effect. Despite an underlying generalized Brillouin zone description, wavefunctions remain delocalized. In addition, the effect can arise in skin-effect models as entirely separate distinguishable feature.
Inverse-Designed Silicon Nitride Nanophotonics
Toby Bi,
Shuangyou Zhang,
Egemen Bostan,
Danxian Liu,
Aditya Paul,
Olga Ohletz,
Irina Harder,
Yaojing Zhang,
Alekhya Ghosh, et al.
Nature Communications
17
6943
(2026)
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Silicon nitride photonics has enabled integration of a variety of components for applications in linear and nonlinear optics, including telecommunications, optical clocks, astrocombs, bio-sensing, and LiDAR. With the advent of inverse design – where desired device performance is specified and closely achieved through iterative, gradient-based optimisation – and the increasing availability of silicon nitride photonics via foundries, it is now feasible to expand the photonic design library beyond the limits of traditional approaches and unlock new functionalities. In this work, we present inverse-designed photonics on a silicon nitride platform and demonstrate both the design capabilities and experimental verification by realising precisely tailored wavelength-division multiplexers, mode-division multiplexers, and high-Q resonators with controllable wavelength range and dispersion. This demonstrates inverse-designed enhanced manipulation of orthogonal bases of light. Furthermore, we use these inverse-designed structures to form optical cavities that hold promise for on-chip nonlinear and quantum optics experiments.
The oscillating electric field emitted by excitons in layered antiferromagnets reveals how quasiparticles synchronize into collective coherence and shows that a complex multi-peak spectrum can arise from a single excitonic resonance dynamically modulated by spin and lattice excitations.
Atom-Photon Bound States in Fractal Photonic Lattices: Localization Length and Anomalous Diffusion
We study atom-photon bound states seeded by two-level emitters coupled to self-similar photonic lattices. By expressing the photonic Green's function through the heat kernel, we show that the far-field localization length obeys xi ~ Delta^(-1/dw), with the detuning Delta from the lower spectral edge and the walk dimension dw of the underlying fractal. This scaling is controlled by anomalous diffusion and does not rely on translational invariance or a band-edge effective-mass approximation. Exact diagonalization on Sierpiński gaskets, pyramids, Vicsek graphs, and Sierpiński carpets confirms the far-field prediction once the bath Hamiltonian is rendered Laplacian-like by compensating the local inhomogeneity in the connectivities with on-site potentials. In the near field, the bound-state amplitude exhibits an additional algebraic variation. For nested finitely ramified fractals, the corresponding exponent agrees with the classical resistance/first-passage scaling, whereas Sierpiński carpets display clear deviations from this simple law. Our results extend structured-bath waveguide QED to self-similar non-periodic geometries and connect bound-state profiles to transport exponents of the underlying fractal lattice.
From order to chaos in a chip-scale Kerr parametric oscillator
Luca O. Trinchão,
Juan Diego Mazo-Vásquez,
Miguel Nienstedt,
Luiz Peres,
Julius Gohsrich,
Eduardo S. Gonçalves,
Alekhya Ghosh,
Arghadeep Pal,
Laís Fujii dos Santos, et al.
Integrated photonics has enabled a wide class of chip-scale light sources and quantum technologies. Within this field, microresonator-based degenerate optical parametric oscillators (DOPOs) have gained prominence. Above a critical power threshold, these systems undergo spontaneous symmetry breaking to settle into one of two stable, π-phase-shifted states -- a mechanism successfully used for quantum random number generation and photonic Ising machines. Here, we show that DOPOs based on the Kerr nonlinearity host a significantly broader range of nonlinear dynamics than previously explored. Using a silicon nitride microring resonator, we experimentally identify Hopf bifurcations that trigger a transition from stationary operation to self-sustained oscillations at MHz frequencies. By adjusting pump detunings and powers, we achieve turnkey control over these oscillatory regimes, navigating the system between stable binary states and periodic limit cycles. Furthermore, we report the experimental observation of period-doubling bifurcations, which numerical simulations reveal as the precursor to a cascading instability culminating in chaos at elevated pump powers. Our results establish a framework for controlling nonlinear instabilities in chip-scale parametric oscillators, with applications in programmable photonic hardware and dynamical optical computing.
Glycan atlassing enables functional tracing of cell state
Dijo Moonnukandathil Joseph,
Nazlican Yurekli,
Sarah Fritsche,
Reem Hashem,
Oana-Maria Thoma,
Imen Larafa,
Tina Boric,
Chloé Bielawski,
Karim Almahayni, et al.
The glycocalyx is a complex layer of glycosylated molecules that surrounds all cells in the human body. It is involved in regulating critical cellular processes, including immune response modulation, cell adhesion and host–pathogen interactions. Despite these insights, the functional relationship between the glycocalyx architecture and cellular state has remained elusive, largely due to the structural diversity of glycocalyx constituents and their nanoscale organization. Here we show that DNA-tagged lectin labelling and metabolic oligosaccharide engineering enable multiplexed super-resolution microscopy of the glycocalyx constituents, yielding an atlas of glycocalyx architecture with nanometre resolution. Quantitative analysis of the obtained nanoscale map of glycocalyx constituents facilitates the extraction of characteristic spatial relationships that accurately report on the cellular state. We demonstrate the capacity of our approach, which we term glycan atlassing, across cell and tissue types, ranging from cultured cell lines to primary immune cells, neurons and primary patient tissue. Glycan atlassing establishes a transformative strategy for investigating glycocalyx remodelling in development and disease, potentially enabling the development of glycocalyx-centred targets in diagnosis and therapy.
Spectral Riemann sheet topology of gapped non-Hermitian systems
We show topological configurations of the complex-valued spectra in gapped non-Hermitian systems. These arise when the distinctive EPs in the energy Riemann sheets of such models are annihilated after threading them across the boundary of the Brillouin zone. This results in a non-trivially closed branch cut that is protected by an energy gap in the spectrum. Their presence or absence establishes topologically distinct configurations for fully non-degenerate systems and tuning between them requires a closing of the gap, forming exceptional point degeneracies. We provide an outlook toward experimental realizations in metasurfaces and single-photon interferometry.
Real-time monitoring of multimode squeezing
Mahmoud Kalash,
Aditya Sudharsanam,
M. H. M. Passos,
Valentina Parigi,
Maria Chekhova
Nature Communications
17
3904
(2026)
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Multimode squeezed light is a key resource for high-dimensional quantum technologies, enhancing metrological sensitivity, boosting communication security, and enabling parallel processing in computation. Its practical potential, however, remains constrained by the inherent single-mode operation of homodyne detection, necessitating post-processing for multimode characterization. Here, we overcome this long-standing challenge by employing multimode optical parametric amplification, enabling loss-tolerant direct detection of squeezing in each mode, which in turn permits mode sorting after amplification. As a result, we demonstrate, for the first time to the best of our knowledge, the real-time monitoring of multimode squeezing. With a spatial light modulator sorting the modes, we simultaneously measure squeezing in nine spatial modes co-propagating within one beam. Although mode sorting and filtering reduce the detection efficiency to less than 0.3%, we observe high-purity squeezing of up to − 7.9 ± 0.6 dB – to the best of our knowledge, the highest squeezing recorded for pulsed light. Furthermore, we demonstrate real-time, loss-tolerant characterization of continuous-variable entanglement and extend it to the detection of cluster states. Similar methods can be applied in the frequency domain, facilitating a crucial capability for scalable quantum technologies.
Organic molecules as single-photon sources
Alexey Shkarin,
Stephan Götzinger
Applied Physics Reviews
13
021312
(2026)
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The development of single-photon sources has been nothing but rapid in recent years, with quantum emitter-based systems showing especially impressive progress. In this paper, we give an overview of the developments in single-photon sources based on single molecules. We will introduce polycyclic hydrocarbons as the most commonly used emitter systems for the realization of an organic solid-state single-photon source. At cryogenic temperatures, this special class of fluorescent molecules demonstrates remarkable optical properties such as negligible dephasing, indefinite photostability, and high photon rates, which make them attractive as fundamental building blocks in emerging quantum technologies. To better understand the general properties and limitations of these molecules, we discuss sample preparation and relevant emitter parameters such as absorption and emission spectra, lifetime, and dephasing. We will also give an overview of light extraction strategies as a crucial part of a single-photon source. Finally, we conclude with a look into the future, displaying current challenges and possible solutions.
Neuromorphic computing with optomechanical oscillators
Andrea Gaspari,
Rémi Avriller,
Florian Marquardt,
Fabio Pistolesi
The increasing resource demands of artificial neural networks have prompted the exploration of novel platforms better suited for machine learning. In this context, phase oscillators represent a promising candidate due to their intrinsic nonlinearity and their ability to exhibit collective synchronization when coupled together. In the present work, we investigate one such implementation: a network of optomechanical oscillators pumped in the blue-detuned regime to achieve self-sustained oscillations. We propose a theoretical framework to describe their dynamics and demonstrate how such systems can be employed for neuromorphic computing. We discuss how they can be trained and analyze a platform, based on drum resonators, that could enable their physical implementation. Ultimately, the theoretical results obtained from modelling an XOR gate using 5 nodes in an all-to-all configuration are discussed.
Vectorial light in Fabry-Pérot resonators in the normal-dispersion regime
Graeme N. Campbell,
Lewis Hill,
Pascal Del'Haye,
Gian-Luca Oppo
Physical Review A
113
043505
(2026)
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The ranges of existence and stability of dark cavity-soliton stationary states in a Fabry-Pérot resonator with a Kerr nonlinear medium, vectorial polarization components, and normal dispersion are determined. The Fabry-Pérot configuration introduces nonlocal coupling that shifts the cavity detuning by the round-trip average power of the intracavity field. When compared with ring resonators, nonlocal coupling leads to strongly detuned dark cavity solitons that exist over a wide range of detunings. We study symmetry breaking between fields of opposite circular polarization characterized by a codimension-2 bifurcation point unique to the regime of normal group velocity dispersion. We show the spontaneous formation of regular dark soliton crystals separated by Turing patterns of alternating polarization via ‘‘self-crystallization’’ due to long-range interactions. Frequency combs of dark soliton crystals of two orthogonal polarizations in Fabry-Pérot resonators display three separate components corresponding to the cavity repetition rate, the wavelength of the periodic pattern, and the soliton lattice spacing. The system also displays the formation of stationary and dynamical vectorial dark-bright solitons. These solutions are different from previous realizations with bichromatic driving in ring resonators, are composed of locked switching fronts, and can undergo Hopf bifurcations when scanning the detuning. Interacting oscillating dark-bright solitons display antiphase dynamics that changes first into quasiperiodic oscillations and then into in-phase dynamics when increasing the cavity length.
A Helmholtz Equation for Surface Plasmon Polaritons on Curved Interfaces: Controlling Cooperativity with Geometric Potentials
Surface plasmon polaritons propagating along curved metal-dielectric interfaces experience geometry-induced modifications absent on flat surfaces. In this work, we derive a covariant, effective two-dimensional wave equation for the transverse magnetic surface plasmon mode on weakly curved smooth interfaces. By perturbatively expanding Maxwell's equations with curvature-adapted boundary conditions, we find a Helmholtz equation with two geometric potential terms that enter at first order in the extrinsic curvature: an isotropic contribution proportional to the extrinsic curvature, and an anisotropic operator arising from the traceless part of the second fundamental form. These linear-in-curvature potentials distinguish convex from concave interfaces, in contrast to the quadratic potentials known from symmetrically confined systems such as dielectric waveguides. We show that our equation reproduces established results for spherical and cylindrical interfaces. We furthermore predict that the anisotropic contribution vanishes when the ratio of the material permittivities equals the square of the golden ratio. As an application, we demonstrate sign-dependent cooperative frequency shifts as well as a curvature-driven redistribution of superradiant and subradiant decay rates for a ring of quantum emitters on a curved metallic spheroid interacting through the surface plasmons.
Orbital Optimization and Neural-Network-Assisted Configuration Interaction Calculations of Rydberg States
Gianluca Levi,
Max Kroesbergen,
Louis Thirion,
Yorick L. A. Schmerwitz,
Elvar Ö. Jónsson,
Pavlo Bilous,
Philipp Hansmann,
Hannes Jónsson
Journal of Chemical Theory and Computation
22
3260-3267
(2026)
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Rydberg excited states of molecules pose a challenge for electronic structure calculations because of their highly diffuse electron distribution. Even large and elaborate atomic basis sets tend to underrepresent the long-range tail, overly confining the Rydberg state. An approach is presented here where the molecular orbitals are variationally optimized for the excited state using a plane wave basis set in a Hartree–Fock calculation, followed by a configuration interaction calculation. The use of excited state optimized orbitals greatly enhances the convergence of the many-body calculation, as illustrated by a full configuration interaction calculation of the 2s Rydberg state of H2. A neural-network-based selective configuration interaction approach is then applied to calculations of 3s and 3p states of H2O and NH3. The obtained values of excitation energy are in close agreement with experimental measurements as well as previous many-body calculations where sufficiently diffuse atomic basis sets were used. Calculations using atomic basis sets lacking extra diffuse functions, such as aug-cc-pVTZ, give significantly higher estimates due to confinement of the Rydberg states.
Broadly tunable quantum-enhanced Raman microscopy for advancing bioimaging
Dmitrii Akatev,
Yijian Meng,
Jonathan Brewer,
Maria Chekhova,
Ulrik L. Andersen,
Mikael Lassen
Stimulated Raman scattering (SRS) microscopy has emerged as a powerful technique for probing the spatiotemporal dynamics of molecular bonds with exceptional sensitivity, resolution, and speed. However, classically, its performance remains fundamentally constrained by optical shot noise, which imposes a strict limit on detection sensitivity and speed. Here, we demonstrate a quantum-enhanced SRS microscopy platform that circumvents this barrier by harnessing amplitude-squeezed light. Specifically, we generate a Stokes beam with 5.2 dB of amplitude squeezing using traveling-wave optical parametric amplification in second-order nonlinear waveguides, and combine it with a tunable coherent pump to access vibrational modes spanning from 1000 to 3100 cm−1. Applied to quantum imaging of metabolites in biological tissue (pork muscle), our quantum-enhanced Raman microscope achieves an average noise suppression of 3.6 dB and a 51% enhancement in signal-to-noise ratio (SNR)— to the best of our knowledge, the largest improvement reported to date in quantum-enhanced SRS microscopy of biological samples.
Diffractive Neural Networks for High‐Throughput Classification of Objects in Microfluidic Systems
Jingli Li,
Steffen Schoenhardt,
Jeffrey Harmon,
Jochen Guck,
Min Gu,
Elena Goi
Advanced Photonics Research
7
e202500272
(2026)
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The integration of optical imaging and machine learning on microfluidic platforms makes it possible to achieve high-content minimally invasive characterization of a population of samples on a single chip As the analysis of this high-content information is typically conducted in the electronic domain optoelectronic conversion speeds and the bandwidth available for data processing put a limitation on the throughput of these methods In this work we present an analysis system based on diffractive neural networks with the potential for integration in microfluidic systems for high-content classification of objects with high sampling rates We show that such a system can distinguish objects by size through passive optical inference with a numerical test accuracy of 98.2 and an experimental test accuracy of 83.4 in an environment compatible with a microfluidic chamber This development paves the way for novel approaches in high-speed phenotyping of large cell populations based on all-optical or hybrid optoelectronic neuromorphic information processing.
Spatial resource dynamics control resistance escape
Nico Appold,
Timon Citak,
Auguste Palm,
Jona Kayser
The evolution of therapy resistance in structured populations such as biofilms and solid tumours is shaped by emergent spatial organization, with pro-found consequences for evolution-based therapies. However, how treatment reshapes these patterns remains poorly understood. Here we show that intermittent treatment pulses transiently reconfigure the resource landscape, reorganize spatial growth zones, and can enable resistant mutants to escape spatial confinement and drive therapy failure. We introduce a spatial evolution assay in which populations expand from single, genetically tailored yeast cells, enabling quantitative tracking of the full spatiotemporal trajectories of continually emerging resistant mutants under intermittent treatment. By integrating these observations with a mechanistically interpretable \textit{in silico} model in a real-to-sim-to-real loop, we identify an effective phase transition in schedule space that defines an optimal balance between population control and sustained resistance confinement, which we validate experimentally. Together, our results establish resource-mediated spatial confinement as a central organizing principle of resistance evolution and provide a mechanistic foundation for spatially informed, evolution-based therapies.
Ultrafast nonlinear dynamics of indium tin oxide nanocrystals probed via fieldoscopy
Andreas Herbst,
Anchit Srivastava,
Kilian Scheffter,
Soyeon Jun,
Steffen Gommel,
Luca Rebecchi,
Sidharth Kuriyil,
Andrea Rubino,
Nicolo Petrini, et al.
Scalable, high-speed, small-footprint photonic switching platforms are essential for advancing optical communication. An effective optical switch must operate at high duty cycles with fast recovery times, while maintaining substantial modulation depth and full reversibility. Colloidal nanocrystals, such as indium tin oxide (ITO), offer a scalable platform to meet these requirements. In this work, the transmission of ITO nanocrystals near their epsilon-near-zero wavelength is modulated by two-cycle optical pulses at a repetition rate of one megahertz. The modulator exhibits a broad bandwidth spanning from 2 to 2.5 µm. Sensitive fieldoscopy measurements resolve the transient electric-field response of the ITO for the first time, showing that the modulation remains reversible for excitation fluences up to 1.2 mJ cm−2 with a modulation depth of 10%, and becomes fully irreversible beyond 3.3 mJ cm−2, while reaching modulation depth of up to 20%. Field sampling further indicates that at higher excitation fluences, the relative contribution from the first cycle of the optical pulses is reduced. These findings are crucial for the development of all-optical switching, telecommunications, and sensing technologies capable of operating at terahertz switching frequencies.
Lena Pollinger,
Johannes N. Greve,
Melanie Grosch,
Sara Kaliman,
Shada Abuhattum Hofemeier,
Martin Kräter,
Ina Brauer,
Jan T. Schaefer,
Francesca Pasutto, et al.
Kidney International Reports
11
106343
(2026)
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INTRODUCTION: Pathogenic variants in myosin heavy chain 9 (MYH9) encoding the heavy chain of nonmuscle myosin IIA (NMMIIA) cause autosomal-dominant MYH9-related disease that may include proteinuric kidney disease macrothrombocytopenia cataract sensorineural deafness and elevated liver enzymes. METHODS: Whole exome sequencing and segregation analysis were performed in a patient with end-stage renal disease Histology of kidney and liver biopsies was assessed and blood smears were examined for the presence of Döhle-like bodies Deformability cytometry and monocyte migration assays were performed Immortalized podocytes and primary skin fibroblasts of 1 patient were transfected with plasmids containing MYH9 wild type (WT) or the p.(Arg424Gly) variant Biochemical studies using recombinantly produced proteins were conducted to assess the variant’s impact on adenosine triphosphate (ATP) turnover and motor function. RESULTS: We identified the likely pathogenic heterozygous MYH9 variant c.1270C>G p.(Arg424Gly) in all affected members of a nonconsanguineous family Typical microscopic findings such as Döhle-like bodies or NMMIIA conglomerates were absent Nonetheless all patients presented with proteinuric kidney disease elevated liver enzymes and intermittent thrombocytopenia The altered protein showed increased ATP turnover in the presence of actin and enhanced motor activity under both unloaded and loaded conditions. CONCLUSION: We identified a novel fully segregating MYH9 variant causing MYH9-related disease Based on biochemical findings we report the first gain-of-function variant of MYH9 We propose that the enhanced intrinsic motor activity of the p.(Arg424Gly) variant is a key contributor to the disease mechanism Incorporation of the p.(Arg424Gly) variant into nonmuscle myosin IIA filaments and higher-order actomyosin assemblies may in principle affect actomyosin dynamics.
Dependence of Equilibrium Propagation Training Success on Network Architecture
Qingshan Wang,
Clara C. Wanjura,
Florian Marquardt
The rapid rise of artificial intelligence has led to an unsustainable growth in energy consumption. This has motivated progress in neuromorphic computing and physics-based training of learning machines as alternatives to digital neural networks. Many theoretical studies focus on simple architectures like all-to-all or densely connected layered networks. However, these may be challenging to realize experimentally, e.g. due to connectivity constraints. In this work, we investigate the performance of the widespread physics-based training method of equilibrium propagation for more realistic architectural choices, specifically, locally connected lattices. We train an XY model and explore the influence of architecture on various benchmark tasks, tracking the evolution of spatially distributed responses and couplings during training. Our results show that sparse networks with only local connections can achieve performance comparable to dense networks. Our findings provide guidelines for further scaling up architectures based on equilibrium propagation in realistic settings.
Many challenges arising in Quantum Technology can be successfully addressed using a set of machine learning algorithms collectively known as reinforcement learning (RL), based on adaptive decision-making through interaction with the quantum device. After a concise and intuitive introduction to RL aimed at a broad physics readership, we discuss the key ideas and core concepts in reinforcement learning with a particular focus on quantum systems. We then survey recent progress in RL in all relevant areas. We discuss state preparation in few- and many-body quantum systems, the design and optimization of high-fidelity quantum gates, and the automated construction of quantum circuits, including applications to variational quantum eigensolvers and architecture search. We further highlight the interactive capabilities of RL agents, emphasizing recent progress in quantum feedback control and quantum error correction, and briefly discuss quantum reinforcement learning as well as applications to quantum metrology. The review concludes with a discussion of open challenges -- such as scalability, interpretability, and integration with experimental platforms -- and outlines promising directions for future research. Throughout, we highlight experimental implementations that exemplify the increasing role of reinforcement learning in shaping the development of quantum technologies.
Toward In Situ Monitoring of the Precipitation of Gold Nanoparticles Using In-Fiber Absorption Spectroscopy
Florian Schorn,
Markus Binder,
Cornelia Damm,
Marco Haumann,
Nicolas Joly
The use of hollow-core photonic crystal fibers in operando spectrometry of chemical reactions is a relatively unexplored technology. It can be used in different ways and offers a variety of advantages compared with conventional operando spectrometry, such as a significantly increased path length with a simultaneously reduced volume. We apply fiber absorption spectroscopy here to the synthesis of gold nanoparticles. We measured the rate of formation of gold nanoparticles at different initial concentrations. We show that much higher resolution is possible with this technique in comparison with a conventional measurement technique using cuvettes.
A 25 THz bandwidth THz spectroscopy system exploiting BNA crystals and a tunable single-ring-fiber pulse compressor
Wei Cui,
Aswin Vishnuradhan,
Markus Lippl,
Eeswar Kumar Yalavarthi,
Angela Gamouras,
Nicolas Joly,
Jean-Michel Ménard
We present a terahertz time-domain spectroscopy (THz-TDS) system which accesses a broadband spectrum, efficiently covering the so-called "new THz gap" between 5 and 15 THz and extending beyond 25 THz. The system exploits nonlinear interactions within the organic crystal BNA (N-benzyl-2-methyl-4-nitroaniline) to generate and detect THz radiation upon excitation by a near-infrared (NIR) pulse centered at 1.03 um. To enable broadband THz spectral monitoring, the NIR pulse from a Yb-based solid-state laser undergoes spectral broadening in a gas-filled single-ring hollow-core photonic crystal fiber, followed by pulse compression to achieve durations as short as 31 fs. This approach paves the way for broadband spectroscopy in hard-to-access THz regions using widely available near-infrared ultrafast sources.
Cell viscosity influences haematogenous dissemination and metastatic extravasation of tumour cells
Valentin Gensbittel,
Zeynep Yesilata,
Louis Bochler,
Gautier Follain,
Laurie Nemoz-Billet,
Olivier Lefebvre,
Klemens Uhlmann,
Annabel Larnicol,
Giulia E. M. Ammirati, et al.
Metastases arise from a multistep process during which tumour cells face several microenvironmental mechanical challenges which influence metastatic success However how circulating tumour cells (CTCs) adapt their mechanics to such microenvironments is not fully understood Here we report that the deformability of CTCs affects their haematogenous dissemination and identify mechanical phenotypes that favour metastatic extravasation Combining intravital microscopy with CTC-mimicking elastic beads mechanical tuning in tumour lines and profiling of tumour-patient-derived cells we demonstrate that the inherent mechanical properties of circulating objects dictate their ability to enter constraining vessels We identify cellular viscosity as a rheostat of CTC circulation and arrest and show that cellular viscosity is crucial for efficient extravasation Moreover we find that mechanical properties that favour extravasation and subsequent metastatic outgrowth can be opposite Altogether our results establish CTC viscosity as a key biomechanical parameter that shapes several steps of metastasis.
Thin-film Al0.30Ga0.70As (111) as a ‘flat’ source of high-purity orthogonally polarized entangled photons
Simon Stich,
Vitaliy Sultanov,
Trevor Blaikie,
Qingyu Shi,
Zbig Wasilewski,
Mikhail A. Belkin,
Maria Chekhova
Optics Express
34
1664-1673
(2026)
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Flat-optics platforms offer new opportunities for the generation of entangled photons by relaxing traditional phase-matching constraints, enabling the use of a broader range of nonlinear materials. Among these, gallium arsenide and aluminum gallium arsenide stand out for their exceptionally high second-order nonlinearities, but their conventional orientation (001) has limited their applicability for photon-pair generation. By transitioning to crystals with (111) surface orientation, we overcome these limitations. We demonstrate a flat-optics-based telecom-range SPDC source using Al0.30Ga0.70As that achieves a high photon-pair generation rate per pump power and bandwidth of up to 0.24 Hz/mW/nm. The choice of 30% aluminum concentration allowed us to reduce pump absorption and photoluminescence background for photon-pair generation at telecom wavelengths by at least an order of magnitude compared to that of GaAs. The specific layer orientation facilitates the generation of orthogonally polarized entangled photons, a prerequisite for polarization-entangled states. Rather than directly probing entanglement, we observe the effect of hidden polarization. Our results highlight AlGaAs (111) as a promising platform for scalable quantum photonic sources and shed light on nonclassical polarization effects accessible through flat-optics engineering.
Fine-tuning cell-mimicking polyacrylamide microgels: Sensitivity to microscale reaction conditions in droplet microfluidics
Ruchi Goswami,
Kyoohyun Kim,
Aldo R. Boccaccini,
Jochen Guck,
Salvatore Girardo
Materials and Design
262
115450
(2026)
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Shaping polyacrylamide (PAAm) hydrogels via droplet microfluidics enables production of microgels that mimic cellular physical properties, advancing mechanobiology research. Controlling microgel size and elasticity is essential but challenging, as multiple factors influence polymerization and network formation. Although chemical reactions in microdroplets are generally faster and more uniform than in bulk, these microreactors are highly sensitive: small changes in chemical or physical conditions can cause significant variations in microgel properties. Our study identifies flow conditions as a crucial factor affecting both microgel elasticity and size by modulating interfacial transport during gelation. Using a flow-focusing microfluidic chip, we generated pre-gel droplets with the same composition in an oil phase, systematically varying the PAAm-to-oil flow rate ratio while maintaining a constant total flow rate. This method produced droplets with minimal size variation (<1 µm), but beads exhibited distinct Young’s moduli despite identical monomer concentrations. Further analysis showed that catalyst transport across the oil–water interface strongly impacts polymerization efficiency and network structure. These findings demonstrate that while droplet polymerization offers advantages, reproducible microgel properties demand precise flow control. This work emphasizes the critical role of microfluidic parameter tuning in advancing PAAm microgel applications in biophysics.
Unitary fault-tolerant encoding of Pauli states in surface codes
Luis Colmenarez,
Remmy Zen,
Jan Olle,
Florian Marquardt,
Markus Müller
In fault-tolerant quantum computation, the preparation of logical states is a ubiquitous subroutine, yet significant challenges persist even for the simplest states required. In the present work, we present a unitary, scalable, distance-preserving encoding scheme for preparing Pauli eigenstates in surface codes. Unlike previous unitary approaches whose fault-distance remains constant with increasing code distance, our scheme ensures that the protection offered by the code is preserved during state preparation. Building on strategies discovered by reinforcement learning for the surface-17 code, we generalize the construction to arbitrary code distances and both rotated and unrotated surface codes. The proposed encoding relies only on geometrically local gates, and is therefore fully compatible with planar 2D qubit connectivity, and it achieves circuit depth scaling as O(d), consistent with fundamental entanglement-generation bounds. We design explicit stabilizer-expanding circuits with and without ancilla-mediated connectivity and analyze their error-propagation behavior. Numerical simulations under depolarizing noise show that our unitary encoding without ancillas outperforms standard stabilizer-measurement-based schemes, reducing logical error rates by up to an order of magnitude. These results make the scheme particularly relevant for platforms such as trapped ions and neutral atoms, where measurements are costly relative to gates and idling noise is considerably weaker than gate noise. Our work bridges the gap between measurement-based and unitary encodings of surface-code states and opens new directions for distance-preserving state preparation in fault-tolerant quantum computation.
Octave-spanning frequency comb from a single-diode-pumped 1 GHz Ti:sapphire laser
Ewan Allan,
Abdullah Alabbadi,
Pablo Castro-Marín,
Hanna Ostapenko,
Pascal Del'Haye,
Derryck T. Reid
Broadband frequency combs with mode spacings of 1 GHz provide a valuable resource for optical frequency metrology and astrophotonics. Significant average powers are often needed to reach the pulse energies required for supercontinuum generation at 1 GHz repetition rates, putting this beyond the reach of most simple ultrafast lasers. Here, by using dispersion-engineered Si₃N₄ waveguides, we report octave-spanning comb generation from 539 to 1078 nm (−20 dB bandwidth) pumped with a three-element 1 GHz Ti:sapphire laser powered by a single laser diode. Laser repetition-rate stability of 790 mHz is achieved over a 1-hour duration, and carrier-envelope-offset control and stabilization to a single-frequency cw laser is presented. The system offers a simple route to a coherent, broadband supercontinuum spanning the visible to the near-infrared, with potential as an enabling technology for optical frequency metrology, quantum timekeeping, and astrophysical spectrograph calibration.
Twisted single-ring hollow-core fiber for broadband chiral detection in nanoliter volumes
Christof Helfrich,
Sonia Maniappan,
Michael Frosz,
Raju Adhikary,
Sandro Colagioia,
Nicolas Joly,
Andrea Marini,
Francesco Tani
Journal of Physics: Photonics
8
015035
(2026)
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The ongoing evolution of hollow-core fibers continues to inspire the development of optofluidic platforms with enhanced sensitivity and minimal sample requirements. Here, we utilize the intrinsic advantages of anti-resonant reflection hollow-core fibers—such as low optical loss and broadband transmission—to realize a twisted single-ring hollow-core fiber (SR-HCF) tailored for polarization-sensitive chiral detection. We optimize the fiber geometry to ensure single-mode operation by strongly attenuating higher-order modes (>50 dB/m) while maintaining low loss for the fundamental mode (<0.1 dB/m) and reducing the sample volume to only ~660 nanoliters per 34 cm fiber length. By applying a constant twist along the fiber length, we minimize birefringence and ensure stable transmission of linear polarization states with polarization extinction ratios (PER) surpassing 38 dB. After injecting an aqueous solution of an optically active molecule, we measure its optical rotation (OR) at different wavelengths with millidegree-level sensitivity and remarkable robustness against misalignment. Measurements with different enantiomeric excess concentrations are in good agreement with independent liquid chromatography characterization.
Solar-pumped lasers, predominantly based on neodymium gain media, offer a promising route to renewable laser-energy conversion and space-based photonics; however, their performance has been constrained by thermal loading and limited power scalability. Here, we propose and numerically investigate a solar-pumped ytterbium thin-disk gain medium in combination with a dome concentrator that enables multipass solar pumping and enhanced absorption. The design yields comparably low lasing thresholds for neodymium- and ytterbium-doped media, while ytterbium provides superior power scalability, enabling up to threefold higher output power. We further identify ytterbium-doped medium combined with a spherical concentrator as a viable solar-pumped, radiation-balanced configuration, achieving self-cooled lasing at solar pump intensities of 28.5 kW cm-2 within the 1020-1033 nm window of the solar spectrum. The spherical concentrator increases the averaged fluence of the solar pump while permitting anti-Stokes fluorescence to escape efficiently. These results establish multi-pass, solar-pumped thin-disk ytterbium lasers as a compact, scalable, and sustainable platform for high-performance solar-pumped lasers
Red Blood Cell-derived Extracellular Vesicles as biomaterials: the opportunity of freezing-induced accelerated aging
Lucia Paolini,
Miriam Romano,
Valentina Mangolini,
Selene Tassoni,
Shuhan Jiang,
Elena Laura Mazzoldi,
Angelo Musicò,
Andrea Zendrini,
Anna Kashkanova, et al.
Biomaterials Science
14
122-139
(2026)
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Red blood cell-derived extracellular vesicles (RBC-EVs) are emerging as promising biomaterials for next-generation drug delivery, owing to their intrinsic biocompatibility, immune evasion properties, and minimal oncogenic risk. However, their broader application is currently limited by unresolved challenges related to heterogeneity, reproducibility, and long-term storage stability. By combining discontinuous sucrose density gradient separation with high-resolution interferometric nanoparticle tracking analysis, we identified a sharp bimodal size distribution of the vesicles in freshly prepared samples. We then tracked how long-term storage at −80 °C drove its conversion into a monomodal distribution. To reproduce these conditions in a shorter time frame, we developed an “accelerated-ageing” protocol based on freeze–thaw cycles that generates RBC-EV samples with homogeneous density, size distribution, and biological activity, effectively replicating the properties of preparations stored for six months at −80 °C. This new vesicle population results stable and retains membrane integrity and cellular internalization capacity, as confirmed by surface-associated enzymatic activity assays and uptake tests in cancer cell lines. These results suggest that freezing-induced “accelerated ageing” represents an effective method for the optimization and standardization of RBC-EVs as building blocks for biomaterial and bioengineering applications.
Soliton self-frequency shift in hollow-core fiber for bright femtosecond radiation tunable across the short-wavelength infrared
Markus Lippl,
Martin Butryn,
Nicolas Joly,
Francesco Tani
We report a fiber-based source of femtosecond radiation that is spectrally tunable in the short-wavelength infrared region, delivering average powers at the multi-watt level. The system utilizes self-soliton frequency shifting in a hydrogen-filled hollow-core fiber, producing pulse trains at 1.1 MHz with integrated relative intensity noise below 0.3% and a polarization extinction ratio of 30 dB. This source constitutes an efficient and valid fiber-based alternative to optical parametric amplifiers for a variety of applications, including THz generation, multiphoton imaging, and high-harmonic generation.
Brillouin–Mandelstam scattering-based cooling of traveling acoustic waves from cryogenic temperatures
Lisa Fischer,
Laura Blázquez Martínez,
Changlong Zhu,
Robin Chenevière,
Johann Troles,
Birgit Stiller
Thermal phonons are a major source of decoherence in quantum mechanical systems. Operating in the quantum ground state is therefore often an experimental prerequisite. In addition to passive cooling in a cryogenic environment, active laser cooling enables the reduction of phonons at specific acoustic frequencies. Brillouin cooling has been used to show efficient reduction of the thermal phonon population in waveguides at GHz frequencies down to 74 K. In this Letter, we demonstrate the cooling of a 7.608 GHz acoustic mode by combining Brillouin active cooling with precooling from 77 K using liquid nitrogen. We show a 69% reduction in the phonon population, resulting in a final temperature of 24.3 +/- 1.9 K, 50 K lower than previously reported.
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