Quantum Physics
Bimodal non-Gaussian photonic states from a single quantum emitter in a waveguide
Thomas Copie, Ofer Firstenberg, G. P. Teja et al. (+2 more)
We investigate the generation of deterministic and heralded non-Gaussian states of light, using a single two-level system coupled to a
chiral waveguide. We study the case of a single two level system driven by pulsed coherent and squeezed drive in a
chiral waveguide. For coherent input pulses, we show that the emitter can deterministically generate Wigner-negative states, albeit of limited rank. Going beyond, using squeezed-
vacuum inputs, we show that the interaction produces rich bimodal non-Gaussian states from which higher-
stellar-rank states, including large squeezed cat states, can be experimentally extracted with a substantial success rate. For experimental feasibility and comparison, we analyze the effect of imperfect coupling and of the intrinsic $50\%$ collection limit of symmetric, non-
chiral waveguides. Following that, we propose a simple interferometric scheme that recovers an effectively
chiral interaction in an otherwise bidirectional waveguide.
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All authors Thomas Copie, Ofer Firstenberg, G. P. Teja, Radim Filip, Hanna Le Jeannic
Fluid Dynamics
A windy sea surface with Stokes waves
Nikhil Yewale, Anil Kumar, Vinod Kumar Kadari et al. (+1 more)
Predicting the transition of wind-forced, gravito-capillary surface waves from smooth to corrugated states remains a longstanding problem in nonlinear surface wave mechanics. Solving driven-dissipative, nonlinear potential flow equations we map these waves ($4-13$ cm) onto a Reynolds number – wave energy phase-space. We identify a transition band separating smooth from corrugated wave states - the wave steepness exhibits a non-monotonic dependence on Reynolds number within this. Subharmonic (in)stability analysis reveals that the fastest-growing mode intensifies corrugations on alternate faces of the carrier wave. Our results offer insights into parasitic capillary wave formation on steep carrier waves and are of interest to ocean remote-sensing.
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All authors Nikhil Yewale, Anil Kumar, Vinod Kumar Kadari, Ratul Dasgupta
Quantum Physics
Iterative linear quadratic regulator on SU(N) for multi-qubit gate synthesis
Dirk Heimann, Felix Wiebe, Elie Mounzer et al. (+1 more)
In
quantum optimal control theory, gradient-based trajectory optimization techniques have proven versatile in designing multi-
qubit quantum gates. Furthermore, incorporating the underlying Lie-group structure can accelerate the optimization process. In this work, we adapt the Lie-group formulation of the iterative linear quadratic regulator (iLQR) to the special
unitary group SU(N) and apply it to
quantum gate synthesis, systematically comparing it against the standard Euclidean iLQR formulation across multiple two- to five-
qubit gates. We find that in the idealized, unconstrained setting, where all Lie-
algebra basis elements are available as drive
Hamiltonian terms, the Lie-group formulation converges faster than the Euclidean iLQR formulation. If drive terms are constrained to 2-local
Hamiltonian terms, the Lie-group variant converges faster in early optimization iterations, but exhibits greater sensitivity to initialization and a stronger tendency towards local minima. These results demonstrate that incorporating Lie-group geometry into iLQR substantially improves convergence and highlight important next steps for improvements in constrained control settings.
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All authors Dirk Heimann, Felix Wiebe, Elie Mounzer, Shivesh Kumar
High Energy Physics (Theory)
Intersection matrices associated to geometric-ordered bases of Feynman integrals
Iris Bree, Federico Gasparotto, Sebastian Pögel et al. (+3 more)
In integration-by-parts reduction of Feynman integrals, the order relation in the Laporta
algorithm determines a set of master integrals. In this paper we investigate the intersection
matrices of the integrands of the master integrals that are obtained from a
geometric order relation. With an appropriate definition of integrands and their duals, we find that the intersection
matrices are simpler than expected: For a filtration-compatible basis, the entries of the intersection
matrix are Laurent
polynomials in the dimensional regularisation parameter $\varepsilon$. For an $\varepsilon$-factorised basis, the entries are instead integers, up to an overall power of $\varepsilon$, if the boundary values for the auxiliary functions of the rotation are chosen appropriately. This has practical consequences: We can systematically eliminate certain auxiliary transcendental functions, introduced in going from a filtration-compatible basis to an $\varepsilon$-factorised basis. We provide an
algorithm that performs this elimination while minimising the number of required calculations.
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All authors Iris Bree, Federico Gasparotto, Sebastian Pögel, Xing Wang, Stefan Weinzierl, Xiaofeng Xu
Chemical Physics
TNASS: Tensor Network Active Space Selection with the Entanglement Feature
Angus Mingare, Isabelle Heuzé and Peter V. Coveney
The quality of multi-scale modelling techniques in molecular electronic structure calculations, such as
embedding and subspace methods, relies upon the chosen active space. The automation of active space selection is vital for ensuring the accuracy, reproducibility, and scalability in such calculations. In this work, we introduce Tensor Network Active Space Selection using the
Entanglement Feature. Through the isolation of strongly correlated electrons, this method provides a scalable foundation for
embedding methods in multi-scale modelling. By representing the purities of all possible orbital partitions as a
Matrix Product State, our method isolates regions of strong electron correlation without requiring manual preselection of target atoms or the calculation of expensive high-order density
matrices. The results demonstrate that this approach leads to lower ground state energies and more accurate dipole moments than other fully automated selection schemes such as those based solely on single-orbital
entropy or the selection of spatial orbitals around the HOMO/LUMO gap.
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Computational Physics · Cross-listed from math.NA
Analysis of Moment Closures Using $\varphi$-Divergences for Rarefied Dynamics with Binary Collisions and Their Galerkin Discretizations
Michael R. A. Abdelmalik, Irene M. Gamba, Torsten Keßler et al. (+1 more)
This work introduces a robust deterministic framework for approximating solutions of the Boltzmann equation with binary collisions by discretizing their dependence on time, position, and velocity using Galerkin methods. By employing a family of parametric Galerkin closures based on $\varphi$-divergences in velocity space, we derive rigorous hierarchies of moment equations that govern fluid dynamic variables. Addressing the limitation that these closures alone do not guarantee dissipation of a $\varphi$-divergence
entropy for the true binary collision operator, we restore this property by formulating a compatible approximate collision operator tailored to each closure. This constructed operator intrinsically retains fundamental physical properties essential for high-fidelity flow simulations, including Galilean invariance, exact conservation of mass, momentum, and energy, and strict dissipation of a $\varphi$-divergence
entropy. Furthermore, we show that the resulting closed moment systems are symmetric-dissipative, yielding Cauchy problems that are well-posed locally in time. To translate this mathematical foundation into an efficient computational tool, we discretize the position and time variables with an
entropy-stable discontinuous Galerkin (DG) finite element method. The fully implicit,
entropy-stable space-time approach enables time steps far beyond typical CFL-limited step sizes and the direct computation of steady states. The robustness and accuracy of the methodology are verified and validated through numerical simulations on the supersonic nozzle flow of argon, mass flow through a channel, and heat transfer between parallel walls, demonstrating agreement with analytical
benchmarks, experimental measurements, and
stochastic particle simulations.
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All authors Michael R. A. Abdelmalik, Irene M. Gamba, Torsten Keßler, Sergej Rjasanow
Computational Physics
A 3-D Hybrid Numerical Method for Simulating Electromagnetic Fields in Structures with Multiple Inhomogeneous Layered Media
Jie Liu, Taihe Li, Ke Chen et al. (+2 more)
A three-dimensional (3-D) hybrid numerical method (HNM) is presented for electromagnetic scattering in structures with multiple inhomogeneous layered media coupled to an arbitrary 3-D non-layered scattering region. It integrates the 3-D numerical mode-matching (NMM) method with a tree-cotree-based mixed finite element method (MFEM). In the NMM, the fields in the 3-D layered media are reduced to a superposition of 2-D waveguide eigenmodes, while the MFEM discretizes the 3-D scattering region. The HNM thus inherits the dimensionality-reduction advantages of both conventional hybrid MM/FEM and pure NMM. Numerical experiments show that the HNM provides an effcient alternative for scattering problems involving non-layered regions embedded in layered media.
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All authors Jie Liu, Taihe Li, Ke Chen, Mingwei Zhuang, Qing Huo Liu
Materials Science
Epitaxial SiGeSn alloys for CMOS-compatible thermoelectric devices
Patrizio Graziosi, Damiano Marian, Andrea Tomadin et al. (+7 more)
The integration of thermoelectric devices into mainstream microelectronic technological platform could be a major breakthrough in various fields within the so-called Green-IT realm. In this article, the thermoelectric properties of heteroepitaxial SiGeSn
alloys, a novel CMOS compatible material system, are evaluated to assess their possible application in thermoelectric devices. To this purpose, starting from the experimentally low
lattice thermal conductivity of SiGeSn/Ge/Si layers of about $\sim$1-2 W/m$\cdot$K assessed by means of 3-$\omega$ measurements, the figure of merits are calculated through the use of Boltzmann transport equation, taking into account the relevant inter-valley scattering processes, peculiar of this multi-valley material system. Values for the figure of merit $ZT$ exceeding $1$ have been obtained for both p- and n- type material at operating temperatures within the 300—400 K range, i.e. at a typical On-Chip temperatures. In this interval, the predicted power factor also features very competitive values of the order of 20 $\rm{\mu W/cm\cdot K^2}$. Our finding indicates that this new class of Si-based materials has extremely good prospects for real-world applications, and can further stimulate scientific investigation in this ambit.
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All authors Patrizio Graziosi, Damiano Marian, Andrea Tomadin, Stefano Roddaro, Omar Concepción, Johnny Tiscareño-Ramírez, Agnieszka Anna Corley-Wiciak, Dan Buca, Giovanni Capellini, Michele Virgilio
Quantum Physics
Entangling Topological Invariants
Kazuki Ikeda and Yaron Oz
An isolated occupied multiplet may admit local tensor-product descriptions without a globally consistent subsystem structure. We characterize the obstruction by comparing the transition functions of the occupied multiplet with those generated by independent basis changes in the two candidate subsystems. When a decomposition into rank-one sectors over a closed surface is specified, the resulting quotient removes row- and column-additive Chern data and yields mixed Chern classes. Momentum-dependent mixing of the sector labels adds the Gauss–Codazzi
curvature of the moving lines, while in the label-conserving limit the mixed class is measured by a crossed Thouless pump. When only the factor dimensions $p$ and $q$ are specified, the comparison is made at the level of the clutching map of a rank-$pq$ bundle over $S^4$. Product frames generate winding numbers in $q\mathbb Z+p\mathbb Z$, so global factorization is possible exactly when $C_2$ is divisible by $\gcd(p,q)$; in particular, odd $C_2$ obstructs a $2\times2$ factorization. We illustrate the two settings with finite eight-level
Hamiltonians and give pumping and occupied-projector
tomography protocols for their readout.
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Quantum Physics
Sample-half-inserted quantum interferometer
Wei Li, Tao Xie, Yu-Hang Luo et al. (+11 more)
Quantum technologies have been widely recognized as unprecedented opportunities for ultra-high precision metrology. As a celebrated example in modern
quantum optics, the Hong-Ou-Mandel (HOM) interferometer is well-known for enabling temporal resolutions on the attosecond scale. However, the relatively low Fisher information per trial in ordinary HOM measurements typically necessitates tens of thousands of repetitions to achieve such precision. Here, we propose and demonstrate a sample-half-inserted HOM (SHOM) interferometer, which enhances the Fisher information by five orders of magnitude in a single interference event. By introducing an asymmetric
photon-sample interaction, the SHOM configuration produces a distinctive dip-bump-dip interference structure, converting what was previously viewed as an artifact into a helpful metrological resource. Experimentally, we measured the optical path difference with an average precision of 4.09 nm (13.63 as) and an average accuracy of 1.22 nm (4.07 as) using $O(10^7)$
photons. Our results establish SHOM interferometry as an efficient phase-insensitive approach, not only paving the way toward practical
quantum-enhanced thickness measurement for transparent materials, but also serving as an elegant strategy to improve the performance of various
quantum devices.
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All authors Wei Li, Tao Xie, Yu-Hang Luo, Kang Zheng, Meiyu Peng, Hui Yang, Chunling Ding, Chen-Zhi Yuan, Omar S. Magana-Loaiza, Keyu Xia, Ryosuke Shimizu, Hui Jing, Chenglong You, Rui-Bo Jin
Mesoscale and Nanoscale Physics
Enhancement of far-field thermal emission via polaritonic cavity modes
Maelie Coral, Jose Ordonez-Miranda, Georges Hamaoui et al. (+5 more)
Controlling thermal emission is crucial for applications involving thermophotovoltaics, thermal sensing, imaging, and camouflage. While prior studies focused on the emission of thermally excited guided modes (TEGMs) inside cavities, their contribution to the far-field radiation outside cavities has remained unexplored. Here, we demonstrate a tunable far-field thermal channel enabled by TEGMs arising from the coupling of surface
phonon-polaritons and cavity resonances. By combining infrared emissivity experiments with fluctuational electrodynamics simulations, we identify distinct spectral features marking the conversion of two-dimensionally confined polaritonic modes into three-dimensional radiative channels. We find that silicon cavities covered with SiO2 enhance the emissivity by up to 200% near the polaritonic spectral resonance, whereas bare silicon cavities yield only broadband enhancement. These findings provide experimental evidence of TEGMs and establish a simple cavity architecture as an effective and scalable platform for tailoring thermal radiation without complex nanofabrication.
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All authors Maelie Coral, Jose Ordonez-Miranda, Georges Hamaoui, Roman Anufriev, Laurent Jalabert, Masahiro Nomura, Yannick De Wilde, Sebastian Volz
Statistical Mechanics
Lower bounds on entropy production from dynamical correlation functions
Paul Raux, Alexander M. Maier and Udo Seifert
Entropy production is a key property in
stochastic thermodynamics. For partially observed and coarse-grained systems, its inference is challenging and typically rests on proven lower bounds. We derive two versions of such bounds based on the asymmetry of experimentally accessible two-time correlation functions of coarse-grained state observables. For non-
equilibrium steady states, the bound is valid for arbitrary correlation lag. For time-dependent processes, it requires the limit of vanishing lag. These bounds hold true for any system that follows either a Markovian dynamics or a coupled set of overdamped Langevin equations on some underlying, unobservable level of description. We illustrate the bounds for both types of dynamics and discuss their optimization and potential tightness.
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Physics and Society
Measuring the engine of a liquidation cascade: subcritical branching inside a first-order transition
Ramon Marc Garcia Seuma
We study seven major crypto-perpetual liquidation cascades (2022-2025), and in the largest of them we can watch the mechanism directly. From the on-chain fill log of a fully transparent venue we measure the branching ratio of that event – the October 2025 crash, the largest on record – in flight, with both of its factors observed and no free constants. It ran deeply subcritical: the structural ratio and the amplification bookkeeping both place it at $\hat\lambda \approx 0.1-0.2$ throughout, while a third, flow-based
estimator falls through the climax rather than rising. All three agree on subcriticality within the venue, not on a common numerical level. Alongside them, 88% of all post-onset forced selling landed within thirty minutes and 63% of it was absorbed off-book by the venue's backstop, which drives the branching ratio down precisely at the climax. Across the full set of seven, at onset – the minute ending the steepest hour of each crash – the order parameter (mean inter-asset coupling) jumps by between 1.6 and 4.4 baseline standard deviations into a near-fully-ordered phase, while the susceptibility proxy $\chi$ collapses in five of the seven events and diverges in none; the jump is invariant under subsampling. The transition is abrupt and scale-robust rather than critical, and its in-cascade signature lives in the liquidity sector: price impact spikes on two venues and two instruments while open interest clears by 25-70%. The natural mechanistic account, a Galton-Watson cascade with $\lambda = k \tilde\rho$, is then eliminated as a description of the pre-cascade state: both of its falsifiable predictions fail at simulated power >= 0.96, on proxied and on directly measured regressors alike. Severity is set by shock times map-in-path times liquidity withdrawal rather than by a diverging multiplier, which is why none of the scalar pre-state measures we can construct grades it.
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Materials Science
Toward two dimensional MoS2 electrets
Eugenio Lunedei, Andrea Liscio, Francesco Borgatti et al. (+8 more)
Here, we show that controlled sulfur vacancy engineering converts monolayer MoS2 into an electret, imparting the ability to store quasi-permanent electrostatic charge within a single atomic layer. Sulfur vacancies are generated with submicrometer spatial control by stamp-assisted electrode-free electrochemical nanolithography, yielding programmable defect densities from 10 10 to 10 13 1 cm-2. The resulting vacancy domains act as deep electron traps and produce surface charge densities up to 1 uCcm-2, with charge retention in the order of hundreds days under ambient conditions. Kelvin probe and electric force microscopies directly reveal stable electrostatic patterns that replicate the lithographic motif. The same vacancy landscape simultaneously defines
exciton-quenching regions, generating co-localized optical and electrostatic contrast and reducing the apparent
exciton lifetime from 15 ns to 180 ps through enhanced nonradiative recombination. The persistence of the optical response over one year identifies sulfur vacancies, rather than transient charge states, as the origin of the patterned functionality. These results establish defect-engineered MoS2 as the first two-dimensional electret and demonstrate that atomic vacancies can be exploited as functional elements for encoding electrostatic and excitonic behavior in a single atomic layer.
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All authors Eugenio Lunedei, Andrea Liscio, Francesco Borgatti, Edoardo Chini, Pasquale DAngelo, Fiorenza Esposito, Niccolo Borghi, Matteo Mannini, Denis Gentili, Luca Seravalli, Massimiliano Cavallini
Adaptation and Self-Organizing Systems · Cross-listed from math.DS
Predicting the occurrence of Braess paradox in the synchronization threshold of coupled oscillator systems
Justin Arches, Emmanuel Fleurantin, Matt Holzer et al. (+2 more)
We study Braess-type paradoxes in coupled oscillator networks where the addition of an edge to the network leads to an increase in the critical coupling required for the existence of a stable phase-locked synchronized solution. By introducing a continuous edge-weight parameter and constructing an augmented system that allows application of the Implicit Function
Theorem, we derive an explicit first-order formula for the sensitivity of the critical coupling, $K'_c(0)$, to small changes in the network structure. This formula reveals that an edge is locally Braess if the ordering of the oscillators being coupled is opposite the ordering of their components in the critical eigenvector at the saddle-node bifurcation, providing a simple criterion for Braess paradox to occur. We then employ this local approximation as a predictor for the occurrence of Braess paradox when the edge is fully incorporated in the network. This prediction is tested numerically in several classes of random networks, demonstrating both high predictive fidelity and the nonlinear limitations of the local approximation. We also examine several explicit examples, highlighting possible motifs by which Braess-type paradoxes occur. Together, these results establish a predictive framework for understanding how incremental changes in network
topology can produce counterintuitive synchronization outcomes.
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All authors Justin Arches, Emmanuel Fleurantin, Matt Holzer, Siddhant Sood, Shakeeb Uddin
High Energy Astrophysical Phenomena
General-relativistic structure of two-component quantum dark fermion stars
Ilídio Lopes
We develop a general-relativistic framework for two-component
quantum dark
fermion stars:
equilibrium configurations of two degenerate
fermion species governed by
gravity, a Yukawa-mediated dark fifth force and a globally relevant Bohm
quantum-pressure correction. The treatment retains the full covariant form of the nonlinear Klein–Gordon equation in the Schwarzschild interior, with closure relations valid at arbitrary compactness, from the ultralight baseline up to densities of order $0.16\,\mathrm{fm}^{-3}$ at which relativistic scalar densities and self-consistent effective
fermion masses become unavoidable. Two Lagrangian parameters, the dark-
fermion mass and the dimensionless ratio between the Yukawa channel and
gravity, together fix the
equilibrium structure; a joint measurement of mass and radius therefore constrains the dark-sector microphysics directly from gravitational-wave observables. For particle masses in the band $10^{-11}$–$10^{-10}$ eV, the configurations exhibit radii of $3$-$24\,\mathrm{km}$ and compactness in the range $0.14$-$0.34$, behaving as dual mimickers: at moderate compactness they overlap with
neutron stars in mass, radius, and inspiral frequency; at the most compact end ($\kappa\sim 0.34$, $R_T/R_S\simeq 1.5$) they cross the
photon sphere and could masquerade as low-mass black holes in the mass-gap region.
Tidal-deformability measurements discriminate against both populations: the dimensionless
tidal deformability is measurably smaller than the
neutron-
star value yet remains non-zero, unlike that of a genuine black hole. These objects populate the sensitivity bands of LISA, the Einstein
Telescope, and
Cosmic Explorer, producing astrometric microlensing signatures individually resolvable by
Gaia. The framework thus provides a reproducible and falsifiable template for constraining dark-sector properties through multi-messenger observations.
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Optics
A 100x Faster Beam Propagation Method for Nonlinear Optical Wave Propagation Based on Discrete Exterior Calculus
Amgad Abdrabou and R. El-Ganainy
Efficient simulation of nonlinear light propagation in complex photonic structures remains a major challenge because these systems combine intricate transverse geometries with propagation over distances spanning many diffraction lengths. Existing numerical methods often require computationally intensive uniform discretizations or struggle to accurately represent complex material boundaries, limiting the practical simulation of multiscale nonlinear photonic devices. Here we introduce a computational framework for solving the nonlinear Schrödinger equation that accelerates simulations by more than two orders of magnitude (over 100x) compared with conventional approaches while maintaining spectral-level accuracy, thereby reducing the computational time required to solve large-scale and multiscale problems from days to hours. The method is based on discrete exterior calculus, enabling geometry-conforming discretization directly on unstructured meshes without the weak formulations required by conventional finite-element methods. In contrast to
Fourier-based spectral solvers, it avoids global oversampling, eliminates Gibbs-type oscillations at material interfaces, naturally incorporates absorbing boundary conditions, and preserves the topological structure of the underlying differential operators. A key feature of the framework is that higher-order propagation operators are generated algorithmically from lower-order discrete operators, providing a systematic route to extending simulations beyond the standard nonlinear Schrödinger equation.
Benchmarks on fundamental
solitons, asymmetric beams, and optical
vortices confirm spectral-level accuracy while demonstrating computational speedups exceeding 100x.
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Soft Condensed Matter
Theory of Handedness Selection in Helices of Chiral Polymers and Biopolymers
Biman Bagchi
Helices are among the most common ordered structures in biological and synthetic
polymers, but their formation involves more than local conformational preference. A finite helix must nucleate, grow, resist breaking, and maintain a selected handedness against thermal fluctuations. We develop a three-state Ising-like transfer-
matrix theory in which each segment is coil-like, right-handed helical, or left-handed helical. This formulation separates ordinary helix–coil cooperativity from the persistence of handedness. The right–left symmetric problem decomposes into symmetric and antisymmetric sectors, giving two characteristic lengths: the helical correlation length $\xi_H$ and the
chiral persistence length $\xi_\chi$. In the strongly helical rare-wall limit, $\xi_\chi\simeq (1/2)\exp[\beta(K+J)]$. A local
chiral bias, motivated by the Ramachandran landscape, is then amplified over finite helical domains.
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High Energy Astrophysical Phenomena
A JWST redshift for the host galaxy of EP250207b of z=3.2: a collapsar origin is viable
Agnes P. C. van Hoof, Peter G. Jonker, Andrew J. Levan et al. (+24 more)
We present James Webb Space
Telescope (JWST) and Hubble Space
Telescope (HST) observations of the field of the fast X-ray transient (FXT) detected by Einstein Probe, EP250207b, to resolve any ambiguity about the host
galaxy and
redshift of the FXT. EP250207b was originally associated with a nearby
galaxy at z=0.082, based on its low chance
alignment probability, and a binary
neutron star merger origin was proposed. However, we report the detection of a background
galaxy at z=3.2 at the location of EP250207b. Assuming this
galaxy is the actual host
galaxy, the rest-frame energetics and timescales of the event change. Furthermore, the available data are not able to rule out the presence of a
supernova associated with EP250207b if at this
redshift. We model the X-ray, optical, near-infrared and
radio light curves using a tophat jet model implemented in Redback and find that they are consistent with an on-axis gamma ray burst afterglow. The energetics and host
galaxy properties do not allow us to distinguish between a collapsar and a merger driven event.
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All authors Agnes P. C. van Hoof, Peter G. Jonker, Andrew J. Levan, Nial R. Tanvir, Franz E. Bauer, Joe Bright, Francesco Carotenuto, Ting-Wan Chen, Ashley Chrimes, Gregory Corcoran, Laura Cotter, Joyce N. D. van Dalen, Rob A.J. Eyles-Ferris, Morgan Fraser, Daniele B. Malesani, Daniel Mata Sánchez, Antonio Martin-Carrillo, Paul O'Brien, Francesca Onori, Jonathan Quirola-Vásquez, Maria E. Ravasio, Andrea Rossi, Javi Sánchez-Sierras, Nikhil Sarin, Steve Schulze, Hui Sun, Manuel A.P. Torres
Quantum Physics
Generation and Enhancement of Bipartite and Tripartite Entanglement in an Electro-Optomechanical Ring Cavity
Fouad Essaadi, Yassine Oussarhan, Mohamed Ouhammou et al. (+4 more)
This study investigates the generation and enhancement of
quantum entanglement in an electro-optomechanical ring cavity system. The setup integrates two Coulomb-coupled mechanical resonators, which serve as the fundamental mechanism for the generation of bipartite and tripartite
entanglement via charge mediated coupling. We then demonstrate the significant enhancement of this
entanglement via a nonlinear parametric drive (an optical parametric amplifier, OPA), which injects a controllable nonlinearity into the cavity. We derive the system's
Hamiltonian and the corresponding
quantum Langevin equations, which are linearized around steady-state solutions to analyze Gaussian
quantum fluctuations. Employing the covariance
matrix formalism, we quantify bipartite
entanglement via logarithmic negativity and tripartite
entanglement via the minimum residual contangle. Our results unequivocally show that while the Coulomb interaction is indispensable for creating
entanglement, the OPA acts as a powerful control tool, dramatically amplifying the degree of
quantum correlations for all subsystems. We find that the strength of
entanglement is highly sensitive to several parameters and can be optimized through the strategic selection of the OPA's gain and phase, the
laser detuning, and the input power. A key finding is the existence of a trade-off, where parameters that maximize
entanglement also constrain the stable operating regime of the system. Furthermore, thermal noise is shown to progressively degrade all
quantum correlations, underscoring the necessity for low-temperature operation. These findings provide comprehensive guidance for parameter optimization, outlining a clear path from generation to enhancement, and highlight the potential of such hybrid systems as versatile platforms for controlling multipartite
entanglement in
quantum technologies.
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All authors Fouad Essaadi, Yassine Oussarhan, Mohamed Ouhammou, Said Mouslih, Mohamed Jakha, Bouzid Manaut, Souad Taj
Astrophysics of Galaxies
MIGHTEE-HI / LADUMA: Investigating the link between baryons and dynamics with 130 resolved HI-selected galaxies
Andreea A Vărăşteanu, Matt J. Jarvis, Harry Desmond et al. (+15 more)
The baryonic Tully-Fisher relation (bTFR) and the radial acceleration relation (RAR) link the observed dynamics in
galaxies to that expected from their baryonic mass distributions. The relations' small intrinsic scatters place strong constraints on
galaxy formation models, dark matter properties and theories of modified dynamics, yet detailed measurements beyond the very local Universe remain limited. We use 130 purely HI-selected
galaxies with resolved HI kinematics and baryonic mass profiles to measure the bTFR and RAR up to $z\approx0.09$. We measure a tight RAR with an acceleration scale $a_0=(1.50\pm0.05)\times10^{-10},{\rm m,s^{-2}}$ and an intrinsic scatter of $0.096\pm0.006$ dex, consistent with local results. We fit the bTFR in the `inverse' direction, conditioning on $M_{\rm bar}$ to mitigate HI flux-related selection effects, measuring a logarithmic slope of $0.27\pm0.01$ (corresponding to a forward slope of $3.72\pm0.16$), with vertical intrinsic scatter $\sigma_\perp\approx0.05$ dex. Fitting the general $\delta$-family of MOND interpolating functions to the RAR, we infer $\delta=4.10^{+1.4}_{-0.68}$, consistent with the value required by
Solar System gravitational constraints and a null Wide Binary Test. We find no significant
redshift evolution in the RAR acceleration scale for our pure HI-selected sample. However, the bTFR zero-point shows an apparent evolutionary trend that is strongly dependent on the fit direction: the traditional forward fit yields an $8.7\sigma$ preference for $z$
evolution, while for our fiducial inverse fit, this reduces to $3.4\sigma$, within $\approx2\sigma$ of the RAR
evolution constraint. This suggests selection effects bias the forward fit; a careful consideration of such effects will be required in future endeavours to robustly measure the
redshift evolution of dynamical scaling relations.
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All authors Andreea A Vărăşteanu, Matt J. Jarvis, Harry Desmond, Anastasia A. Ponomareva, Tariq Yasin, Michalina Maksymowicz-Maciata, Ian Heywood, Natasha Maddox, Andrew J. Baker, Laurent Chemin, Martin Meyer, Danail Obreschkow, Kristine Spekkens, Natalia Stylianou, Rohan G. Varadaraj, Marcin Glowacki, Maarten Baes, Abhisek Mohapatra
Materials Science
Strain Tuning of Orbital-Driven Giant Magnetoresistance in van der Waals ferrimagnet Mn$_3$Si$_2$Te$_6$
Abdul Ahad, Miuko Tanaka, Shunta Aoki et al. (+7 more)
Strain engineering of magnetotransport offers a powerful strategy for uncovering emergent electronic and domain phenomena in
quantum magnetic materials, while providing a promising pathway toward next-generation mechanically programmable spintronic technologies. Van der Waals magnets are particularly attractive in this context because their high crystallinity and mechanical flexibility allow exceptionally large, precisely controllable strain, enabling access to strain-induced functionalities unattainable in conventional solids. Here, we report systematic strain control of the van der Waals magnet Mn$_3$Si$_2$Te$_6$, which exhibits an unconventional colossal magnetoresistance whose microscopic origin remains under debate. We demonstrate in situ large-strain modulation of the electrical resistance in bulk
crystals and show that the effect can be consistently explained by strain-tunable
chiral orbital-current domains. Furthermore, measurements on exfoliated flake devices containing a single
chiral domain reveal direct strain control of the electronic structure affected by orbital
magnetic moment, establishing a unified microscopic mechanism for the unconventional colossal magnetoresistance. These results identify strain as an exceptionally effective control parameter for tailoring electronic and
magnetic states in van der Waals magnets and provide a conceptual framework for realizing
spin-straintronic functionalities based on orbital degrees of freedom.
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All authors Abdul Ahad, Miuko Tanaka, Shunta Aoki, Darius-Alexandru Deaconu, Varun Shah, Tenta Kitamura, Hao Ou, Mohammad Saeed Bahramy, Jiang Pu, Toshiya Ideue
Soft Condensed Matter
Control of collective activity to crystallize an oscillator gas
Marine Le Blay, Joshua H.K. Saldi and Alexandre Morin
Motility-induced phase separation occurs in assemblies of self-propelled units when activity is coupled negatively to density. In contrast, the consequences of a positive coupling between density and activity on the collective behaviour of active matter remain unexplored. Here, we show that collective activity can emerge from such a positive coupling among non-motile building blocks. We perform experiments with self-sustained oscillators powered by contact-charge electrophoresis. Although the oscillators are non-motile by design, they spontaneously form an active gas when confined together. The super-elastic nature of collisions constitutes a positive density-activity coupling and underlies the active gas properties. Elucidating the origin of binary collisions allows us to precisely control the structure of the active gas and its eventual crystallization. Beyond considering the overlooked positive coupling between density and activity, our work suggests that rich collective properties can emerge not only from the
symmetry of interactions between active building blocks, but also from their adaptable and responsive behaviour.
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Quantum Gases
Faraday pattern formation in dipolar superfluid and supersolid quantum gases
Sumit Semwal, Shawan K. Jha, G. A. Bougas et al. (+2 more)
We investigate Faraday instabilities in three-dimensional parametrically driven trapped dipolar
quantum gases within the framework of the extended Gross-Pitaevskii equation. In the superfluid regime, periodic modulation of the short-range interactions induces the resonant excitation of discrete polygonal surface modes displaying sub-harmonic response. The resonance frequencies and the parametric windows of instability are accurately captured by an appropriate Mathieu equation, further corroborating our simulations. It is also shown that dipolar interactions in superfluids shift the resonance frequencies to lower values compared to their non-dipolar counterparts. Near the superfluid-to-supersolid transition, intrinsic density undulations associated with the softened roton mode accelerate pattern formation, yielding hybrid surface and bulk excitations. The bulk patterns prevail deeper in the supersolid regime, emerging from droplet collisions with the superfluid background. Our results reveal a crossover from surface collective modes to hybrid surface-bulk excitations and demonstrate how parametric driving dictates pattern formation in long-range interacting
quantum fluids.
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All authors Sumit Semwal, Shawan K. Jha, G. A. Bougas, S. I. Mistakidis, Pankaj Kumar Mishra
Quantum Physics
Observation of quantum nonclassicality without freedom of choice in a minimal causal network
Ya Xiao, Yan-Xin Rong, Ran He et al. (+6 more)
Quantum causal networks enable tests of nonclassicality beyond Bell nonlocality while relaxing some physically unwarranted assumptions. By relaxing the freedom-of-choice and spacelike-separation assumptions, the unrelated-confounders causal networks provide a simple and robust route to certify
quantum nonclassicality. Here, we implement the minimal three-node unrelated-confounders network in an optical experiment using two independent polarization-entangled
photon sources and an intervention at the central node, experimentally achieved with a high-fidelity entangling measurement. We employ a causal data-fusion protocol that combines observational and interventional data to significantly improve the protocol's noise tolerance, and observe a violation of the corresponding hybrid causal inequality by more than three standard deviations. Our results provide deeper insights into
quantum nonlocality in networks and highlight the UC network as a compact, experimentally accessible platform for device-independent
quantum protocols that do not require actively chosen measurement settings.
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All authors Ya Xiao, Yan-Xin Rong, Ran He, Yu Meng, Yang Zhang, Xiao-Ye Xu, Yong-Jian Han, Zheng-Hao Liu, Yong-Jian Gu
Strongly Correlated Electrons
Emergence and Detection of Surface altermagnetism in KV$_2$Se$_2$O
Rodrigo Jaeschke-Ubiergo, Xanthe H. Verbeek, Colin Lange et al. (+4 more)
We demonstrate the recent concept of emergent surface altermagnetism through its unique signatures in \KVSO. We show that for bulk antiferromagnetically ordered \KVSO, the (001) surface exhibits $d$-wave altermagnetism. Our results fully explain the recent seemingly contradicgting experimental evidence, independently showing both an antiferromagnetically ordered bulk from
neutron diffraction, and $d$-wave
spin splitting from photoemission spectroscopy. To fully verify this conecept, we predict, as a key experimental signature, a large nonlinear Edelstein response, which is localized at the surface, and follows the $d$-wave altermagnetic
symmetry. These results are not only relevant for the metallic and room-temperature magnet \KVSO, but also for several other Lieb
lattice systems. Our work expands the pool of techniques that can be used to detect altermagnetism emerging at the surfaces of antiferromagnets.
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All authors Rodrigo Jaeschke-Ubiergo, Xanthe H. Verbeek, Colin Lange, Sergio Rodriguez, Atasi Chakraborty, Alexander Mook, Jairo Sinov
Quantum Physics
Gravitational redshift as a quantum channel: modeling the effects of gravitational redshift in quantum optics
Thomas Mieling, Andreas Wolfgang Schell and David Edward Bruschi
The gravitational frequency shift of light is well understood in the theory of classical electromagnetism. Nevertheless, its description in
quantum theory is not yet fully developed. Recent work pointed out inconsistencies in previously developed models aimed at describing the gravitational
redshift as an effective multi-mode mixer (MMM) acting on modes of light, but so far a complete solution of these issues was not obtained. Here, we identify the root cause of the MMM model's inconsistency and provide two complementary approaches to correct it: a "natural" one from a field-theoretic perspective, and another adapted to the
language of
quantum mechanics of finite-dimensional systems. We show that the second approach allows for modeling of the
redshift in a multi-mode transmission setup as a
quantum channel that can be characterized using standard
quantum information-theoretic techniques when restricting the input states to Gaussian states of light.
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Optics
AOM-based ultra-low noise laser intensity control up to the MHz range
Christian Partes, Jonas Auch, Eduard Heidt et al. (+3 more)
High-power
laser sources that exhibit low relative intensity noise and allow simultaneous dynamic control of their light level are required for a broad range of applications in various fields of physics. Acousto-optic modulators (AOMs) are widely used for active power stabilization and regulation due to their simple drive electronics requirements and high optical power handling capability in free-space. However, the rather slow propagation speed of the sound wave within the AOM
crystal typically limits their control bandwidth to a few hundred kHz. In this work, we present a novel AOM-based control system that is capable of significantly suppressing intensity noise of high-power
lasers up to the MHz range. By combining two standard feedback loops with one feedforward control branch and optimizing the beam path in the AOM
crystal, ultra-low relative intensity noise levels down to $-155\, \text{dB}\,\text{Hz}^{-1}$ even at several hundred kHz are achieved. Our results are relevant for applications that require ultra-low intensity noise at
Fourier frequencies up to the MHz range, such as optical
lattice experiments with light ultracold atoms.
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All authors Christian Partes, Jonas Auch, Eduard Heidt, Kirill Karpov, Florian Kiesel, Christian Groß
Strongly Correlated Electrons
Manipulation of localized excitons in CrPS$_4$ by temperature and magnetic field
Dipankar Jana, Swagata Acharya, Amit Pawbake et al. (+9 more)
Layered van der Waals
magnetic semiconductors provide a versatile platform for exploring excitonic phenomena intertwined with
spin and
lattice degrees of freedom, enabling
excitons to act as sensitive probes of
magnetic order. CrPS$_4$ is a layered
antiferromagnetic semiconductor that hosts rich excitonic features whose microscopic origin and connection to
magnetic ordering remain incompletely understood. Here, we investigate the electronic and excitonic properties of bulk CrPS$_4$ using a combination of many-body perturbation theory, dynamical mean-field theory, and photoluminescence-based experiments. Our calculations establish CrPS$_4$ as a direct-gap
semiconductor with a bandgap of 2.48~eV in the
antiferromagnetic phase. Several sub-bandgap excitonic transitions are predicted by theory, comprising multiple
spin-allowed
excitons and an additional
spin-flip excitation, predominantly localized on the Cr$^{3+}$ ions. Temperature- and
magnetic-field-dependent optical measurements reveal thermally driven
exciton redistribution among localized states and identify characteristic energy shifts that provide clear optical signatures of
magnetic phase transitions in CrPS$_4$. These results provide new insights into the excitonic transitions of antiferromagnets and suggest potential routes for all-optical sensing and light-driven control of their
magnetic order.
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All authors Dipankar Jana, Swagata Acharya, Amit Pawbake, Dmitrii Litvinov, Aljoscha Soll, Zdenek Sofer, Clement Faugeras, Dimitar Pashov, Mark van Schilfgaarde, Kostya S. Novoselov, Marek Potemski, Maciej Koperski
General Relativity and Quantum Cosmology
Semiclassical Black Hole-White Hole transitions: an analytical treatment
Julio Arrechea, Stefano Liberati and Massimiliano Spadafora
Recent numerical studies of semiclassical
gravity suggest that, in spherically symmetric black holes with both outer and inner horizons, the semiclassical instability of the inner horizon can drive the complete evaporation of the trapped region on timescales shorter than the standard Hawking evaporation time. Independent simulations further indicate that the disappearance of the trapped region is followed by the formation of an anti-trapped region, i.e.~a dynamical white hole. In this work, we develop an analytic treatment of
quantum effects in trapped and anti-trapped regions, showing how these numerical results can be understood within simplified two-dimensional models. We consider collapse models describing the formation of charged and regular black holes and compute the renormalized stress-energy tensor of the $|\textit{in}\rangle$
vacuum state. We show that, within this framework, the emergence of an anti-trapped region is a generic consequence of the amplification of negative energy fluxes propagating along the outgoing direction inside the initial trapped region. This provides an analytic explanation for the black-hole-to-white-hole transition observed in numerical simulations. Our analysis further suggests that the fluxes generated by the subsequent anti-trapped region, now propagating along the ingoing direction, may trigger the formation of a new trapped region. This raises the possibility of a cascade of black-to-white-hole transitions, potentially ending in a horizon-free, bouncing spacetime without invoking additional
quantum-gravitational dynamics. Although establishing the complete
evolution requires a self-consistent treatment of semiclassical backreaction, our framework identifies which features of the mechanism are universal and which depend on the geometry, laying the groundwork for a systematic investigation of semiclassical black-hole-to-white-hole transitions.
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