Materials Science · Cross-listed from physics.app-ph
A Diamagnetic, Light-Driven Tesla Engine Based on a Mechanically Displaced, Magnetically Levitated Graphene Disk
Tian Tong, Feng Lin, Wei Zhang et al. (+11 more)
Ferromagnetic materials are widely used in Tesla thermomagnetic engines, whereas diamagnetic counterparts have remained unexplored. Here, we demonstrate the first diamagnetic Tesla engine by exploiting the strong diamagnetism of
graphene. A
graphene disk, fabricated by stacking
graphene sheets, serves as the engine wheel. We first show that the conventional Tesla engine design using a permanent magnet placed near the disk edge to create unbalanced thermomagnetic forces under asymmetric local heating fails to generate rotation. We achieve stable operation by laterally displacing the levitated disk from
equilibrium, creating a strong restoring force that drives rotation under light excitation. Calculations and measurements establish the displacement-dependent force, with an optimal offset of 0.8 mm yielding speeds up to 2000 rpm under
laser heating and 1000 rpm under direct sunlight. Adding vanes allows the disk to function as a gear, powering a
graphene vehicle and transferring energy to another disk. This design utilizes the strong and anisotropic diamagnetism of
graphene and paves the way for light-powered sensors, actuators, and micro-vehicles.
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All authors Tian Tong, Feng Lin, Wei Zhang, Runjia Li, Xinxin Xing, Zhuochen Duan, Chunhui Xu, Bing Tu, Zhaoping Liu, Xufeng Zhou, Zhiming Wang, Dong Liu, Jonathan Hu, Jiming Bao
Other Condensed Matter · Cross-listed from physics.bio-ph
A physicist-friendly primer on the Hamiltonian for quantum sensing in proteins: analytical expressions and insights for a toy model of the radical-pair mechanism
Clarice D. Aiello, Brian L. Ross, Alessandro Lodesani et al. (+1 more)
Electron
spin-dependent chemical reactions in
proteins, often discussed under the 'radical-pair mechanism', remain the leading microscopic proposal for
magnetic field sensing in biology. Yet the essential physics is often obscured by the complexity of realistic models. In this work, we present a physicist-friendly primer on the simplest radical-pair
Hamiltonian that already captures many of the mechanism's best-known qualitative features. The contributions of this work are fourfold. First, we place on record a complete analytical solution of this toy model, which has previously been studied extensively, mostly through numerical and partial analytical approaches. Working in the experimentally relevant singlet-triplet basis, we derive closed-form expressions for the instantaneous singlet population and for two related time-averaged singlet yields. Second, we introduce a new interpretation of these results that makes several familiar features of radical-pair physics transparent. In particular, we show that the dynamics admit a bright-dark decomposition (in the sense of
spin mixing), similar to structures studied in atomic physics. Third, through this bright-dark perspective, we clarify experimentally relevant features of the toy model. In particular, we show that the so-called 'low-field effect' arises from a coherence term between bright and dark sectors, and that the special role of zero field is best understood as a phase-locking phenomenon rather than merely as enhanced mixing. Fourth, we import methods developed in the context of technological
quantum sensing to obtain further insight into the model. This allows us to clarify the role of initial state preparation and the trade-off between coherent phase accumulation and time-averaging penalties. The resulting toy model serves both as an analytically tractable
benchmark and as a conceptual starting point for future work.
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All authors Clarice D. Aiello, Brian L. Ross, Alessandro Lodesani, Morgan L. Sosa
Materials Science · Cross-listed from quant-ph
Fault-tolerant simulation of the electronic structure using Projector Augmented-Waves and Bloch orbitals
Rishabh Bhardwaj, Alexander Reed Muñoz, Travis E. Jones et al. (+1 more)
Strongly correlated materials are a natural target for fault-tolerant
quantum computers, but they require tools beyond those developed for molecules. Electronic wavefunctions vary rapidly near
nuclei yet remain delocalized across many unit
cells, and bulk properties must be converged systematically with respect to finite-size errors. To resolve such issues, we present the Bloch–UPAW framework that combines Bloch-orbital $k$-space structure with
unitary projector-augmented-wave (UPAW) augmentation. The UPAW
Hamiltonian, expressed directly in the Bloch basis, retains explicit control of Brillouin-zone sampling, and incorporates near-
nuclear physics through strictly local on-site corrections. The construction is independent of the underlying one-particle representation, so it applies to both plane-wave and localized bases, and it handles supercells for
symmetry-breaking phenomena more efficiently. We derive a linear-combination-of-
unitaries decomposition and a block-encoding
circuit suitable for qubitization; UPAW augmentation adds one ancilla
qubit and no Toffoli gates at leading order relative to a Bloch-only block encoding. Asymptotically, the Toffoli cost scales as $\mathcal{O}(N_k^3)$ when refining the $k$-mesh and as $\mathcal{O}(N_a^{3.5})$ when enlarging the supercell, enabling convergence to be steered by the most favorable route for a given material. Resource estimates for bulk diamond show approximately an order-of-magnitude reduction in Toffoli count relative to prior work on periodic solids.
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All authors Rishabh Bhardwaj, Alexander Reed Muñoz, Travis E. Jones, John Golden
Materials Science · Cross-listed from cs.LG
XANE(3): An E(3)-Equivariant Graph Neural Network for Accurate Prediction of XANES Spectra from Atomic Structures
Vitor F. Grizzi, Luke N. Pretzie, Jiayi Xu et al. (+1 more)
We present XANE(3), a physics-based E(3)-equivariant graph neural network for predicting X-ray absorption near-edge structure (XANES) spectra directly from atomic structures. The model combines tensor-product message passing with spherical harmonic edge features, absorber-query
attention pooling, custom equivariant layer normalization, adaptive gated residual connections, and a spectral readout based on a multi-scale Gaussian basis with an optional sigmoidal background term. To improve line-shape fidelity, training is performed with a composite objective that includes pointwise spectral reconstruction together with first- and second-derivative matching terms. We evaluate the model on a
dataset of 5,941 FDMNES simulations of iron
oxide surface facets and obtain a spectrum mean squared error of $1.0 \times 10^{-3}$ on the test set. The model accurately reproduces the main edge structure, relative peak intensities, pre-edge features, and post-edge oscillations. Ablation studies show that the derivative-aware objective, custom equivariant normalization, absorber-conditioned
attention pooling, adaptive gated residual mixing, and global background term each improve performance. Interestingly, a capacity-matched scalar-only variant achieves comparable pointwise reconstruction error but reduced derivative-level fidelity, indicating that explicit tensorial channels are not strictly required for low intensity error on this
dataset, although they remain beneficial for capturing finer spectral structure. These results establish XANE(3) as an accurate and efficient surrogate for XANES simulation and offer a promising route toward accelerated spectral prediction, ML-assisted spectroscopy, and data-driven materials discovery.
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All authors Vitor F. Grizzi, Luke N. Pretzie, Jiayi Xu, Cong Liu
Soft Condensed Matter
Disentangling microstructural elements of shear thickening suspensions via computer simulations of a minimal model
William C. J. Buchholtz, Daniel L. Blair, Jeffrey S. Urbach et al. (+2 more)
We use a minimal model for a dense suspension undergoing thickening and thinning to investigate microstructural changes in 2d simulations. Our simulations show that in steady flow the contact network contains distinct building blocks which are clearly signaled by sharp peaks in the radial distribution function, similar to what is observed in granular jamming. These structures {deform} during thinning. Non-Gaussian stress fluctuations that only emerge during thickening are associated to power law tails in the distribution of local contact forces, which tend to emerge when the flow-induced building blocks form large spanning assemblies. The subset of the contact network characterized by strong contact forces and connectivity large enough to be rigid or over-constrained is increasingly likely to percolate as the system starts to thicken, and to percolate over larger strain windows during thickening. The tendency of these structures to span the sample and to persist is dramatically reduced during thinning, where instead their deformation allows for a more homogeneous spatial redistribution of contact forces, significantly reducing the fluctuations of the macroscopic stress over time.
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All authors William C. J. Buchholtz, Daniel L. Blair, Jeffrey S. Urbach, H. A. Vinutha, Emanuela Del Gado
Soft Condensed Matter
Preserving elastic anisotropy with tessellations of granular packings
Annie Z. Xia, Dong Wang, Catherine La Riviere et al. (+3 more)
Multiscale periodic metamaterials have been designed for numerous applications, such as impact absorption, acoustic cloaking, photonic band gaps, and mechanical logic gates. This prior work has focused on optimizing mesoscale structure for desired bulk isotropic properties. In contrast, we seek to develop materials with highly anisotropic elastic properties. To quantify elastic anisotropy, we introduce two rotationally invariant, normalized quantities that characterize the anisotropic response to shear and compression, respectively, $A_G$ and $A_C$. We find that typical crystalline solids possess average elastic anisotropy $\overline{A}_G \approx 0.15$ and $\overline{A}_C \approx 0.09$. Compared to atomic
crystals, jammed granular materials can attain elastic anisotropies that are several orders of magnitude larger. Since grain rearrangements reduce anisotropy in granular materials, to preserve strong elastic anisotropy, we design tessellated granular materials that consist of multiple connected grain-filled voxels, which limit rearrangements and enable highly anisotropic elastic properties. Bulk granular packings with $N$ grains prepared at pressure $p$ have maximal anisotropy for $pN^2\sim1$ and become isotropic in the large-$pN^2$ limit. We show that homogeneously tessellated granular systems can inherit the elastic response of the constituent voxel configurations with elastic anisotropy up to $100$ times that of crystalline compounds over a range of $pN^2$. We show further methods to tune the elastic anisotropy of tessellations by designing heterogeneously patterned voxel configurations and tessellations that allow large boundary deformations.
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All authors Annie Z. Xia, Dong Wang, Catherine La Riviere, Rebecca Kramer-Bottiglio, Mark D. Shattuck, Corey S. O'Hern
Quantum Gases · Cross-listed from physics.atom-ph
Limits of Statistical Models of Ultracold Complex Lifetimes
Kevin B. Xu and John L. Bohn
The puzzle of "sticky collisions," in which molecular collision complexes exhibit unexpectedly long lifetimes, remains an unresolved mystery. A central challenge to solving this mystery is that traditional close-coupling calculations remain limited by the vast computational cost needed to take into account all the degrees of freedom involved in the collision. In this work, we propose a statistical model designed to simulate the result of full close-coupling calculations, with the goal of collecting statistics about reasonable lifetimes of collision complexes. To do so, we numerically sample resonances using random
matrix theory and utilize results from
quantum defect theory to calculate scattering properties and lifetimes. We find that in the limit of dense resonances, our theory agrees well with the Rice-Ramsperger-Kassel-Markus (RRKM) prediction, whereas in the limit of sparse resonances, the physics is governed by threshold behavior rather than resonant effects. By comparing these predictions to experimental results in two limits, we argue that close-coupling calculations alone may be insufficient to resolve the issue of long lifetimes.
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Soft Condensed Matter
Local Rules for Directing the Emergence of Global Properties in Complex Structures
Andrew Slezak and Varda F. Hagh
From ants to caterpillars, many biological systems composed of simple builders have been observed to construct complex, adaptive, and functional architectures without requiring complete access to the global state of the structure. In these systems, global function emerges from the accumulation of local actions, as individual builders follow local rules to manipulate, modify, and deposit material in response to local environmental stimuli. This raises the question of how local rules can be selected for simple builders so that desired functions reliably emerge as a natural consequence of their interactions with their environment. We propose a systematic framework for determining such rules and demonstrate its effectiveness using a minimal model inspired by tent caterpillars and their silk networks. Using our framework, we show that local rules can be designed so that when simple builders follow them during network construction, the values of several emergent properties including area coverage, mean line density, and front
curvature can be directed toward specific target values. We use a statistical approach to determine how rules can be modified to increase the probability that a useful local change occurs, the magnitude of that change, or both, so that the target property can be achieved reliably. Our results demonstrate a general strategy for linking local rules to emergent global properties in complex structures. This strategy offers a step toward fabricating functional structures using simple builders in uncertain environments where global information, precise control, and sustained human supervision are infeasible.
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Quantum Gases
Phase-space origin of superfluid stability in ring Bose-Einstein condensates
M. O. C. Pires
We present a kinetic description of superfluid currents in ring-shaped Bose-Einstein condensates based on the Wigner phase-space formalism. Starting from the Gross-Pitaevskii equation in a toroidal geometry, we derive a Vlasov-type equation for the angular Wigner function, in which the mean-field interaction generates an effective force proportional to the density gradient. Within this framework, we obtain the dispersion relation of collective modes and recover the Bogoliubov spectrum in the long-wavelength limit. We show that the Landau criterion for superfluidity can be interpreted as the absence of resonant phase-space trajectories satisfying the condition \(\omega = q v_\ell\). In a ring geometry, the quantization of angular momentum leads to a discrete set of velocities, which suppresses the availability of resonant states and strongly inhibits Landau damping. In contrast, in the continuous limit \(R \to \infty\), the spectrum becomes quasi-continuous and the standard Landau damping mechanism is recovered, establishing a direct connection between kinetic resonances and the energetic criterion for superfluidity. We further analyze the role of Bogoliubov depletion by considering a finite-width angular momentum distribution. Although resonant states formally exist in this case, we show that, for flow velocities below the sound velocity, the phase-space distribution does not provide the gradients required for energy transfer, and the superfluid current remains dynamically stable. Our results provide a unified phase-space interpretation of superfluidity, highlighting the role of angular momentum quantization and the structure of the distribution function in determining the stability of persistent currents.
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Other Condensed Matter · Cross-listed from physics.chem-ph
Surface Plasmons in the Continuum
Mohit Chaudhary, Hans-Christian Weissker, Daniele Toffoli et al. (+5 more)
The interest to foster plasmonic applications at energies in the ultra-violet, has escalated research initiatives in clusters of unconventional plasmonic materials like aluminum and indium,for which the surface-plasmon resonance appears above the ionization potential. Naturally, the
quantum mechanical description calls for the incorporation of the ionization process, thereby making the ab initio calculations challenging. We present a robust approach within the time-
evolution formalism of the time-dependent density-functional theory to calculate surface plasmon resonance in the continuum of metal clusters. Using the much studied Al$_{13}^-$ as a system of reference, we show that accurate description of the continuum and of the ionization of the cluster allow to capture a broad surface-plasmon in the UV. Application of this approach in aluminum clusters has given the size-dependent
evolution from discrete spectral features in Al$_{6}$ to the surface-plasmon in larger clusters in the deep ultra-violet.
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All authors Mohit Chaudhary, Hans-Christian Weissker, Daniele Toffoli, Mauro Stener, Victor Despré, Franck Rabilloud, Jean Lermé, Rajarshi Sinha-Roy
Statistical Mechanics · Cross-listed from q-bio.PE
Fixation probabilities for multi-allele Moran dynamics with weak selection
Ian Braga, Lucas Wardil and Ricardo Martinez-Garcia
Fixation probabilities are essential for characterizing
stochastic evolutionary dynamics, but analytical results remain limited mainly to systems with two competing types. We develop a perturbative framework to compute fixation probabilities in multi-allele Moran processes under weak selection. Exploiting the general structure of the backward Fokker-Planck operator in this regime, we show that fixation probabilities admit a systematic expansion around their neutral solution. We first introduce the framework for $M$ competing alleles with multivariate
polynomial fitness functions. We then apply it to three biologically motivated examples: a constant-fitness model, which we solve for an arbitrary number of alleles; a three-allele coordination game in which allele fitness increases with its frequency in the population; and a three-allele model of clonal interference between mutualistic alleles. These results extend the analytical understanding of fixation probabilities beyond pairwise interactions, establishing a framework for investigating multi-strategy
stochastic evolutionary dynamics.
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Materials Science · Cross-listed from physics.optics
Atomically-Thin Tsumoite (BiTe) based All-Photonic-Isolator, Information Converter, and Logic-Gate
Saswata Goswami, Caique Campos de Oliveira, Abhijith M.B. et al. (+6 more)
Two-dimensional tsumoite (BiTe), a polymorph of Bi2Te3, has emerged as a promising candidate for nonlinear photonic devices owing to its strong
spin-orbit coupling, tunable bandgap, and high carrier mobility characteristics. This work presents a thorough examination of the third-order nonlinear optical response of BiTe dispersions using spatial self-phase modulation (SSPM) spectroscopy. The nonlinear refractive index (n2) and third-order nonlinear susceptibility are quantitatively derived from the diffraction ring patterns, demonstrating third-order nonlinear susceptibility values, similar to or surpassing those of advanced 2D materials. The temporal development and distortion of the SSPM rings are examined using the wind-chime model, and thermal factors influencing the SSPM pattern are analyzed. First-principles electronic band structure studies reveal that the elevated nonlinear susceptibility arises from band dispersion. Direct correlation between carrier transport and third-order nonlinear susceptibility is established. Utilizing these qualities, all photonic devices, including a photonic isolator based on a 2D BiTe-2D hBN
heterostructure, are depicted to show asymmetric propagation. A photonic information converter and a logic gate are designed using the cross-phase modulation technique. These findings establish 2D BiTe nanostructure as a formidable nonlinear optical platform for advanced photonic signal processing and integrated photonic applications.
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All authors Saswata Goswami, Caique Campos de Oliveira, Abhijith M.B., Varinder Pal, Vidya Kochat, Pulickel M. Ajayan, Samit K. Ray, Pedro A. S. Autreto, Chandra Sekhar Tiwary
Superconductivity
Raman response in superconducting multiorbital systems with application to nickelates
Matías Bejas, Jun Zhan, Xianxin Wu et al. (+2 more)
The recent discovery of high-$T_c$ superconductivity in pressurized and thin film nickelates is nowadays one of the most relevant and active topics in solid-state physics. The origin of superconductivity together with the relevance of multiorbital physics are highly discussed issues in this field. Knowledge of the size of the gap and its
symmetry is of fundamental interest to uncover the superconducting mechanism at play in the nickelates. Electronic Raman scattering is a powerful tool to investigate the main characteristics of the gap. Here, we investigate the Raman response in the superconducting phase for three different models: Two-orbital models, including $d_{x^2-y^2}$ and $d_{z^2}$ orbitals, with one and two layers; as well as a
bilayer model with the $d_{x^2-y^2}$ orbital as the only active one. For each of these models, we consider different pairing
symmetries and determine their characteristic fingerprints in the Raman response. For the two-orbital models, we perform full multiorbital calculations including interorbital and intraorbital scattering, and compare the results with those obtained using the additive Raman response where each band is considered separately. Our results should be useful for discussing the minimal model for superconductivity and its pairing
symmetry in nickelates. The obtained results and discussions, as well as the presented formalism, are also of general interest for other multiorbital systems.
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All authors Matías Bejas, Jun Zhan, Xianxin Wu, Andreas P. Schnyder, Andrés Greco
Mesoscale and Nanoscale Physics
High-harmonic generation in systems with chiral Bloch states: application to rhombohedral graphene
Jessica O. de Almeida, Wilton J. M. Kort-Kamp and Mathias S. Scheurer
Nonlinear light-matter interaction and, in particular, high-harmonic generation (HHG) are fundamentally interesting and frequently discussed as versatile probes of
quantum materials with potential for optical information processing applications. Meanwhile, there has also been significant progress in
graphene-based multilayer systems to engineer interesting band structures and boost correlation effects. Motivated by the successful demonstration of HHG in
graphene, we here study this effect in rhombohedral stacks of $n$ layers of
graphene, a recent very prominent representative of correlated multilayer
graphene systems. We show how the
chiral Bloch states of the valleys of this system crucially affect the HHG. The "winding" of the Bloch states scales linearly with $n$, just like the dominant harmonic order. The location of the strongest
quantum geometry in momentum space on a ring of finite radius is shown to be imprinted on the time-dependent momentum distribution at the beginning of the strong
laser pulse. We further demonstrate that the presence of an interaction-induced splitting of the two valleys leads to a complex interplay of the opposite chiralities of the two valleys, directly visible in the $n$ dependence of the circular dichroism. We also analyze the impact of doping and identify a quantity that tracks the net chirality of the occupied states. Our findings show that rhombohedral
graphene constitutes a promising platform for exploring rich nonlinear optical phenomena.
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Materials Science
Agentic LLM Reasoning in a Self-Driving Laboratory for Air-Sensitive Lithium Halide Spinel Conductors
Yuxing Fei, Bernardus Rendy, Xiaochen Yang et al. (+7 more)
Self-driving laboratories promise to accelerate materials discovery. Yet current automated solid-state synthesis platforms are limited to ambient conditions, thereby precluding their use for air-sensitive materials. Here, we present A-Lab for Glovebox Powder Solid-state Synthesis (A-Lab GPSS), a robotic platform capable of synthesizing and characterizing air-sensitive inorganic materials under strict air-free conditions. By integrating an agentic AI framework into the A-Lab GPSS platform, we structure autonomous experimental design through abductive and inductive
reasoning. We deploy this platform to explore the vast compositional space of lithium halide spinel solid-state ionic conductors. Across a synthesis campaign comprising 352 samples with diverse compositions, the system explores a broad chemical space, experimentally realizing 72% of the 171 possible pairwise combinations among the 19 metals considered in this study. Over the course of the campaign, the fraction of compositions exhibiting both good ionic conductivity (> 0.05 mS/cm) and high halide spinel phase purity increases from 1.33% in the first 75
agent-proposed samples to 5.33% in the final 75. Furthermore, by inspecting the AI's
reasoning processes, we reveal distinct yet complementary discovery strategies: abductive
reasoning interrogates abnormal observations within already explored regions, whereas inductive
reasoning expands the search into broader, previously unvisited chemical space. This work establishes a scalable platform for the autonomous discovery of complex, air-sensitive solid-state materials.
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All authors Yuxing Fei, Bernardus Rendy, Xiaochen Yang, Junhee Woo, Xu Huang, Chang Li, Shilong Wang, David Milsted, Yan Zeng, Gerbrand Ceder
Statistical Mechanics
Perspective: Measuring physical entropy out of equilibrium
Haim Diamant and Gil Ariel
Entropy is one of the key thermodynamic variables reflecting changes in the state of matter. Unlike other thermodynamic variables, it is well-defined also for nonequilibrium steady states through its relation to information. Applying this relation to physical systems is an ongoing challenge, as it requires knowledge of microscopic high-dimensional continuous distributions which is generally unattainable. A set of new approaches for the measurement of
entropy in nonequilibrium steady or absorbing states have been developed and successfully applied to identify dynamic structures and transitions in diverse systems, ranging from jammed packings to swarming bacteria. We briefly review these approaches, emphasizing why applications to physical systems, including those out of
equilibrium, is substantially different from the general statistical challenge of
entropy estimation and inference. We point at promising current and future directions.
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Mesoscale and Nanoscale Physics
Light-Matter-Coupling formalism for magnons: probing quantum geometry with light
Ying Shing Liu, Emil Viñas Boström, Michael A. Sentef et al. (+1 more)
Nontrivial
quantum geometry is a key feature of the wavefunctions of collective
magnetic excitations in topological systems, but accessing it experimentally remains an open challenge. While Raman circular dichroism (RCD) has emerged as a promising probe, the fundamental link between the RCD and
magnon quantum geometry has remained unsettled, and complicated by the fact that
magnons are charge neutral. Here, we identify when and why this link exists. We show that, under broad conditions, the Fleury-Loudon Raman vertex can be obtained directly from a light-matter coupling expansion of the effective
magnon Hamiltonian, bypassing the conventional microscopic derivation based on virtual electronic processes. This yields an analytical connection between the RCD and the Berry
curvature of
magnon bands. Applied to monolayer CrI\textsubscript{3}, our theory predicts finite temperature signatures of topological
magnons in the RCD. These results establish a general route to
quantum-geometry sensitive optical probes in magnonic systems.
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All authors Ying Shing Liu, Emil Viñas Boström, Michael A. Sentef, Silvia Viola Kusminskiy
Materials Science
Isolating Exciton Dissociation Pathways in ReSe$_{\text{2}}$
Bradley G. Guislain, Rysa Greenwood, Matteo Michiardi et al. (+13 more)
Strongly bound
excitons dominate the optical response in many van der Waals
semiconductors, yet distinguishing between the different microscopic processes governing
exciton dissociation remains challenging. Using time- and angle-resolved photoemission spectroscopy (TR-ARPES), we independently track
exciton and band-edge carrier populations in bulk ReSe$_{\text{2}}$ under resonant excitation. By studying the fluence dependence and polarization-controlled
exciton density dependence of the
exciton dissociation process, we distinguish between competing processes and identify
exciton photoionization as the microscopic dissociation mechanism. These results establish a population-resolved strategy for resolving
exciton-to-carrier conversion pathways in strongly excitonic materials.
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All authors Bradley G. Guislain, Rysa Greenwood, Matteo Michiardi, Giorgio Levy, Sergey Zhdanovich, Jerry Icban Dadap, Sydney K.Y. Dufresne, Arthur K. Mills, Dario Armanno, Shawn Lapointe, Francesco Goto, Nicolas Gauthier, Fabio Boschini, Andrea Damascelli, Ziliang Ye, David J. Jones
Strongly Correlated Electrons · Cross-listed from quant-ph
Observation of feedback-directed quantum dynamics in large-scale quantum processors
Ruizhe Shen and Ching Hua Lee
Programmable
quantum hardware provides an emerging platform for exploring and controlling non-
unitary quantum dynamics through measurement-based operations. In this work, we introduce feedback-directed
circuit architectures that integrate spatially structured mid-
circuit measurements with real-time conditional operations to steer the
evolution of random dynamics, and perform their large-scale simulations (up to 100
qubits) on programmable digital
quantum processors. By promoting measurement from a passive readout to an active control signal, these adaptive monitored
circuits enable directional information flow and generate intrinsic asymmetry in random
circuit simulations. We implement this framework on IBM superconducting
quantum processors and observe robust, noise-resilient signatures of feedback-induced asymmetry distinct from the more well-known non-Hermitian skin effect. Our results establish feedback as a programmable resource for non-
unitary control, opening new avenues for engineering measurement-based dynamics, non-
equilibrium phenomena, and tunable open-system behavior on large-scale
quantum hardware.
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Strongly Correlated Electrons
Classification and correlation signatures of chiral spin liquids on the pyrochlore lattice
Chunxiao Liu, Leon Balents and Yasir Iqbal
We present a systematic classification and variational study of
chiral quantum spin liquids on the pyrochlore
lattice based on fermionic parton constructions. Focusing on
chiral $\mathrm{U(1)}$ and $\mathbb{Z}_2$
spin-
liquid Ansätze, we characterize their
symmetry properties, flux structures, and low-energy spinon spectra within a projective
symmetry group framework, and incorporate gauge fluctuations through Gutzwiller-projected wave functions studied by variational Monte Carlo. From the equal-time
spin structure factor, we develop correlation-based diagnostics that distinguish gauge-dominated Coulomb phases from states with substantial matter-field and short-range contributions. Distinct
chiral flux sectors, though close in energy, exhibit markedly different degrees of emergent $\mathrm{U(1)}$ gauge-field dominance, reflected in the geometry and contrast of pinch-point singularities. Although these states are not competitive ground states of the nearest-neighbor Heisenberg model, they define a physically meaningful family of proximate
chiral phases relevant to extended pyrochlore
Hamiltonians.
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Statistical Mechanics · Cross-listed from quant-ph
Quantum Chaos and Eigenstate Thermalization
Rohit Patil and Marcos Rigol
We provide a pedagogical introduction to eigenstate thermalization. This phenomenon, which occurs in generic
quantum many-body systems, allows one to understand why thermalization takes place in isolated systems under
unitary dynamics. We motivate eigenstate thermalization using random
matrix theory and discuss recent complementary results for the volume-law
entanglement entropy of Haar-random states. We discuss numerical results that highlight the corresponding behaviors in
quantum many-body systems.
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Quantum Gases
Three-body interactions in Rydberg lattices
Rhine Samajdar, Mikhail D. Lukin and Valentin Walther
Programmable arrays of neutral Rydberg atoms are one of the leading platforms today for scalable
quantum simulation and computation. In these systems, the dipole-dipole interactions between the individual atoms, or
qubits, typically result in binary – i.e., two-body – couplings. In this work, we develop an experimentally accessible scheme for engineering three-body interactions in Rydberg
lattices. Such strong three-body couplings can fundamentally modify the underlying physics compared to systems with only two-body interactions: we demonstrate this, in particular, by systematically investigating the effective many-body
Hamiltonian and its emergent
quantum phases. This capability paves the way for the
quantum simulation of a broader class of correlated models of condensed matter and high-energy physics.
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Quantum Gases
Localization with Hopping Disorder in a Quasiperiodic Synthetic Momentum Lattice
Joel M. Sunil, J. Bharathi Kannan, Monu Bhartiya et al. (+5 more)
Quasiperiodicity is easily realized with ultracold atoms in optical
lattices and has been used to simulate the delocalization-localization transition. Random local potentials can also be implemented by spatial light modulators. Programmable hopping disorder, however, remains difficult to realize in conventional optical
lattices. Momentum-space
lattice (MSL) offers a platform to address this. We implement the MSL using an $^{87}$Rb Bose-Einstein condensate via multiple Bragg diffraction and
benchmark the platform by simulating wavepacket dynamics with hopping disorder on top of the generalized Aubry-André (GAA) model. We test programmable hopping disorder added to localized/delocalized backgrounds tunable by the Aubry-André potential strength, as well as systems with mobility edges. Uncorrelated hopping disorder smooths the AA transition into a crossover between weakly (large localization lengths) and strongly localized regimes; the resulting enhancement in localization suppresses wavepacket spreading. We also implement spatially correlated hopping disorder and compare its dynamics with uncorrelated disorder of the same final width, demonstrating a correlation-induced enhancement in spreading. Measured dynamics agrees with trends from ideal tight-binding simulations. Trends in non-universal features depending on microscopic structure and short-time dynamics as functions of quasiperiodic potential strength, hopping-disorder strength, and GAA deformation also match numerical results, with better agreement at larger hopping-disorder strengths. Numerical simulations of the MSL dynamics provide insights into sources of corrections. Our results demonstrate that MSL provides a versatile platform for realizing general disordered
quantum systems with programmable hopping amplitudes beyond quasiperiodic models.
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All authors Joel M. Sunil, J. Bharathi Kannan, Monu Bhartiya, Rayees A S, Shuvarati Roy, G. J. Sreejith, M. S. Santhanam, Umakant Rapol
Materials Science
Surface-enhanced Raman scattering and density functional theory study of selected-lanthanide-citrate complexes (lanthanide: Tb, Dy, Ho, Er, Tm, Yb and Lu)
Hao Jin and Yuko S. Yamamoto
In this study, surface-enhanced Raman scattering (SERS) and density functional theory (DFT) calculations were combined to investigate the SERS spectra of Ln-citrate complexes (Ln: Tb, Dy, Ho, Er, Tm, Yb, and Lu) under 488 and 532 nm excitation. Peak assignment was supported by simulated SERS spectra calculated with an optimized DFT method using large-core effective core potentials. The main bands near 935, 1060, 1315, and 1485 cm-1 were assigned to (C-COO-) + (CH2), (CH2) + (C-O – Ln), sym(COO-) + (CH2), and asym(COO-) + (CH2), respectively. Relative peak intensities were evaluated by normalizing the bands near 935, 1060, and 1485 cm-1 to that near 1315 cm-1. The ratios I_935/I_1315 and I_1485/I_1315 generally increased from Dy-citrate to Lu-citrate, whereas the I_1060/I_1315 ratio decreased. These trends were observed under both excitation wavelengths. The decrease in relative SERS peak intensity of the 1060 cm-1 band is attributed to stronger Ln-O interaction and reduced polarizability change, whereas the increases of the 935 and 1485 cm-1 bands are likely related to changes in local electronic distribution and effective
symmetry sensitivity.
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