Strongly Correlated Electrons
Controlled pairing symmetries in a Fermi-Hubbard ladder with band flattening
J. P. Mendonça, S. Biswas, M. Dziurawiec et al. (+6 more)
Band flattening has been identified as key ingredient to correlation phenomena in Moiré materials and beyond. Here, we examine strongly repulsive
fermions on a ladder – a minimal platform for unconventional $d$-wave pairing – and show that flattening of the lower band through an additional diagonal hopping term produces non-
Fermi liquid behavior, evidenced by the violation of Luttinger's
theorem, as well as axial $d$-wave pairing correlations. Alternatively, plaquette ring exchange can also generate pairing, albeit with a distinct diagonal $d$-wave pairing
symmetry. Hence, our finding showcases a competition of different unconventional pairing channels, and demonstrates via a simple model how band geometry can induce fermionic pairing. This offers broadly relevant insights for correlated flat-band systems, ranging from ultracold atoms to strongly interacting electrons in solids.
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All authors J. P. Mendonça, S. Biswas, M. Dziurawiec, U. Bhattacharya, K. Jachymski, M. Aidelsburger, M. Lewenstein, M. M. Maśka, T. Grass
Mesoscale and Nanoscale Physics
Pyroelectric effects in hybrid semiconductor-lithium niobate quantum devices
Manas Ranjan Sahu, Suraj Thapa Magar, Yadav Prasad Kandel et al. (+1 more)
Hybrid
quantum devices using surface acoustic waves show promise as key elements of
quantum information processors. We report measurements of integrated flip-chip devices consisting of
semiconductor quantum dots and surface acoustic wave resonators in lithium niobate. We observed that the pyroelectric effect in lithium niobate inhibited the operation of
quantum dots in the integrated devices. GaAs/AlGaAs devices suffered from unintentional carrier depletion, and Si/SiGe devices suffered from electrostatic discharge. Our results highlight the importance of mitigating pyroelectric effects in
semiconductor-lithium niobate hybrid devices for continued progress in
quantum interconnects and transducers.
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All authors Manas Ranjan Sahu, Suraj Thapa Magar, Yadav Prasad Kandel, John M. Nichol
Statistical Mechanics
An introduction to monitored quantum systems and quantum trajectories: spectrum, typicality, and phases
Ryusuke Hamazaki, Ken Mochizuki, Hisanori Oshima et al. (+1 more)
Thanks to recent experimental advances in simulating and detecting
quantum dynamics with high precision and controllability, our understanding of the physics of monitored
quantum systems has considerably deepened over the past decades. In this article, we provide an introductory theoretical review on the basic formalisms governing open
quantum dynamics under measurement, along with recent developments in their spectral and typical aspects. After reviewing
quantum measurement theory, we introduce the concept of
quantum trajectories, which are the conditional dynamics of monitored states shaped by a set of measurement outcomes. We then discuss the spectral properties of the dynamical map describing the
evolution averaged over measurement outcomes. As has recently been recognized, these spectral features are intimately connected to whether
quantum trajectories exhibit typical behaviors, such as ergodicity and purification. Moreover, we introduce Lyapunov exponents of typical
quantum trajectories and discuss how these quantities serve as indicators of measurement-induced phase transitions in monitored
quantum many-body systems.
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All authors Ryusuke Hamazaki, Ken Mochizuki, Hisanori Oshima, Yohei Fuji
Materials Science
Electronic and magnetic properties of the NdNiO$_2$/SrTiO$_3$ thin films
Sajid Sekh, Andrzej Ptok, Wojciech Brzezicki et al. (+2 more)
The hole-doped NdNiO$_2$ layer deposited on the SrTiO$_{3}$ surface exhibits unconventional superconductivity. Here, we present a systematic study of the electronic and
magnetic properties of the NdNiO$_2$
superconductor using the density functional theory (DFT). The strong local Coulomb interactions in the Ni($3d)$ and Nd($4f$) states are included within the DFT+$U$ method. The effect of Sr doping on the electronic band structure and density of states was studied for the NdNiO$_2$ thin films deposited on the SrTiO$_3$ (001) surface. The results obtained for the uncapped thin films were compared with the calculations for the NdNiO$_2$ films capped by the SrTiO$_3$ layer. We have found significant changes in the electronic structure and
magnetic properties of the thin films compared to the bulk
crystal.
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All authors Sajid Sekh, Andrzej Ptok, Wojciech Brzezicki, Przemysław Piekarz, Andrzej M. Oleś
Materials Science
Anisotropic electron-phonon coupling and chiral phonons in van der Waals room temperature ferromagnet Fe$_{5}$GeTe$_{2}$
Smrutiranjan Mekap, Andrzej Ptok, Jyoti Saini et al. (+3 more)
The layered van der Waals Fe$_5$GeTe$_2$ (F5GT) compound exhibits room-temperature ferromagnetism, making it a promising candidate for technological applications. In our study, combined temperature, wavelength, and polarization-dependent Raman measurements, along with ab initio calculations reveal important aspects of
lattice dynamics and electron-
phonon interactions. The angle-resolved Raman intensity under linear polarization configurations exhibits a strong tilt in the laboratory coordinate system, indicating the existence of anisotropic electron-
phonon coupling. The temperature
evolution of this anisotropy is discussed by extracting the phase factor of the Raman tensor elements from the angle-resolved intensity measured at different temperatures, also uncovering a
spin-orbit coupling-mediated electron-
phonon response in F5GT. The thermal
evolution of electron-
phonon coupling is also examined by measuring the temperature dependence of the Fano parameter of the asymmetric peak in the Raman spectra, while wavelength-dependent measurements establish the role of optical resonance in enhancing the anisotropic interaction. Finally, the threefold rotational
symmetry guarantees the existence of
chiral phonons. We present direct spectroscopic evidence for these
chiral vibrational modes through cross-circularly polarized Raman measurements, complemented by theoretical calculations of
phonon circular polarization. Together, these results identify F5GT as an ideal platform for investigating emergent couplings among
lattice, electronic, and
magnetic degrees of freedom and for advancing the understanding of
chiral phonons in
magnetic van der Waals materials.
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All authors Smrutiranjan Mekap, Andrzej Ptok, Jyoti Saini, Changgu Lee, Subhasis Ghosh, Anushree Roy
Materials Science
Topological character of the antiferromagnetic EuMg$_{2}$Bi$_{2}$
Mazharul Islam Mondal, Issam Mahraj, Milo Sprague et al. (+8 more)
Antiferromagnetic EuM$_{2}$Pn$_{2}$ compounds, where M is a metal element and Pn is a pnictogen element, have been recognized as candidates for realizing a topologically nontrivial electronic structure. In this paper, we focus on EuMg$_2$Bi$_2$, whose topological nature still remains unclear. We present a comprehensive study based on several experimental and theoretical techniques.
Magnetic susceptibility, electrical resistivity, and specific heat capacity measurements confirm the existence of an
antiferromagnetic ordering. The electronic band structure was investigated by high-resolution angle-resolved photoemission spectroscopy (ARPES), supported by ab initio calculations. ARPES measurement reveals that the electronic structure of this system is dominated by linearly dispersive hole-like bands near the
Fermi level. Theoretical analyses of the electronic band structure indicates that EuMg$_2$Bi$_2$ is a strong topological
insulator, which should be reflected in the presence of a metallic surface state. We also theoretically examine the
magnetic-field-induced anomalous
Hall conductivity, confirming previously reported observations.
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All authors Mazharul Islam Mondal, Issam Mahraj, Milo Sprague, Sabin Regmi, Xiaxin Ding, Firoza Kabir, Himanshu Sheokand, Krzysztof Gofryk, Dariusz Kaczorowski, Andrzej Ptok, Madhab Neupane
Materials Science
Three-dimensional atom-by-atom mapping of nanoscale precipitates in single Te inclusions in Cd0.9Zn0.1Te crystal
Eloïse Rahier, Sebastian Koelling, Guillaume Nadal et al. (+3 more)
The complexity and richness of phenomena governing
alloy crystal growth can be unraveled by examining the three-dimensional atomic-level distribution of elements and
impurities incorporated during growth. These species act as atomic fingerprints, revealing the thermodynamic constraints that shape material structure and composition. Herein, we combine transmission electron microscopy and atom probe of tellurium (Te) inclusions within cadmium zinc telluride (CZT) single
crystals. The correlative analysis uncovers nanoscale precipitates embedded within Te inclusions, consisting of CZT nanocrystals with a Zn content of 1.5 at.%. Surrounding these precipitates, an around 10 nm-thick shell is observed, enriched with copper and indium
impurities. In addition, traces of sodium and sulfur are detected within the nanocrystals. These findings provide direct evidence of the complex segregation and precipitation processes occurring during CZT
crystal growth, reflecting the interplay of thermodynamic driving forces and kinetic constraints that govern solute redistribution. The resulting insights contribute to a deeper understanding of
impurity behavior and phase separation mechanisms in CZT
alloys. This work establishes a framework for modeling and optimization of growth strategies of higher-quality CZT
crystals for next-generation infrared and radiation detection technologies.
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All authors Eloïse Rahier, Sebastian Koelling, Guillaume Nadal, Sudarshan Singh, Luc Montpetit, Oussama Moutanabbir
Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
DC-powered broadband quantum-limited microwave amplifier
N. Nehra, N. Bourlet, A. H. Esmaeili et al. (+7 more)
Fast, high-fidelity, single-shot readout of superconducting
qubits in
quantum processors demands
quantum-limited amplifiers to preserve the optimal signal-to-noise ratio. Typically,
quantum-limited amplification is achieved with parametric down-conversion of a strong pump tone, which imposes significant hardware overhead and severely limits scalability. Here, we demonstrate the first DC-powered broadband amplifier operating within 0.2
photons of the
quantum limit. Our impedance-engineered Inelastic Cooper-pair Tunneling Amplifier (ICTA)-a voltage-biased SQUID in which Cooper pairs tunnel inelastically by emitting signal-idler
photon pairs-operates in reflection, delivering 13 dB of average gain across a 3.5 GHz bandwidth in a single stage. Semiclassical simulations accurately predict the gain and saturation power, enabling further design improvements. By eliminating the pump-tone infrastructure, the broadband ICTA promises to dramatically reduce the hardware complexity of
quantum-limited amplification in superconducting
quantum processors.
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All authors N. Nehra, N. Bourlet, A. H. Esmaeili, B. Monge, F. Cyrenne-Bergeron, A. Paquette, M. Arabmohammadi, A. Rogalle, Y. Lapointe, M. Hofheinz
Superconductivity
Metastability and high-Tc superconductivity in A15-type ternary hydride YSbH6 at moderate pressure
Maélie Caussé, Kieran Bozier, Peter I. C. Cooke et al. (+2 more)
The discovery of high-temperature
superconductors remains a central challenge in materials science. Hydrogen-rich compounds are among the most promising candidates, as they can exhibit
phonon-mediated superconductivity at elevated critical temperatures, though their stabilization typically requires extreme pressures. % Here, we report the identification of YSbH$_{6}$ as a promising
superconductor by a multi-stage high-throughput screening on ternary A15-type hydrides, followed by a high-throughput computational search of the Y–Sb–H system, accelerated by ephemeral data derived potentials. % The cubic $Pm\Bar{3}$ YSbH$_{6}$ phase exhibits a predicted critical temperature of 118\,K at 50\,GPa, among the highest $T_{\rm c}$ reported to date for an A15-hydride at this pressure. Thermodynamic analysis shows that YSbH$_{6}$ lies $\sim$100\,meV/atom above the convex hull at 50\,GPa, but only 26\,meV/atom above the hull at 120\,GPa, suggesting possible metastability and synthesis at similar high pressure conditions. The phase is dynamically stable over a wide pressure range (20–120\,GPa), displays kinetic stability at 50\,GPa and elastic stability at 20 and 50\,GPa, key ingredients for long-lived metastable behaviour at moderate pressures. % These results highlight YSbH$_{6}$ as a
benchmark case illustrating the balance between high-$T_{\rm c}$ performance and limited thermodynamic stability in ternary hydrides, and underscore the importance of combined dynamic, thermodynamic, kinetic and elastic stability analyses for guiding experimental synthesis of metastable
superconductors.
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All authors Maélie Caussé, Kieran Bozier, Peter I. C. Cooke, Stefano Racioppi, Chris J. Pickard
Strongly Correlated Electrons
Semi-automated estimation of hydrogenic initial states for localized Wannier functions
Tatsuki Oikawa, Kota Ido, Takahiro Misawa et al. (+2 more)
We present a semi-automated method for obtaining an initial estimate of Wannier functions, designed to facilitate the construction of Wannier functions for describing low-energy effective models of solids, particularly those relevant to strongly correlated electron systems. Our approach automatically determines the hydrogenic projections orbitals and the center of the Wannier functions from information on Bloch wavefunctions at the $\Gamma$ point. This method is integrated into cif2qewan, enabling seamless generation of input files for
Quantum ESPRESSO and Wannier90. We validate our method through applications to both inorganic and organic compounds, such as Si, SrVO$_3$, FeSe, Na$_8$Al$_6$Si$_6$O$_{24}$, and (TMTTF)$_2$PF$_6$. The obtained results demonstrate that our semi-automated projections give a good initial estimate of the Wannier functions. We also show the comparisons with other methods for estimating the initial states of the Wannier functions, such as the Selected Columns of the Density
Matrix (SCDM). Our methodology shows an efficient way to construct Wannier functions, paving the way for high-throughput calculations in the study of complex materials.
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All authors Tatsuki Oikawa, Kota Ido, Takahiro Misawa, Takashi Koretsune, Kazuyoshi Yoshimi
Soft Condensed Matter
A ruled narrow elastic strip model with corrected energy
E. Vitral, J. A. Hanna and L. Koens
We present a new one-dimensional model for elastic strips based on a nondevelopable ruled surface. An auxiliary field regularizes the Sadowsky narrow-strip model to allow nonzero twist with vanishing
curvature. The energy exhibits the scalings derived by Freddi and co-workers, and for a certain choice of parameter, convexifies the Sadowsky energy without patching. We present the kinematics and energetics of the model, and employ a variational approach featuring a rotation tensor to derive
equilibrium equations. We perform a regular perturbation expansion to study the model behavior close to inflection points. When the energy is convex,
curvature and moment are continuous at inflection points, while the auxiliary function suffers a jump, leading to a discontinuity in the ruled
embedding for any finite width.
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Soft Condensed Matter
A Unified Thermo-Chemo-Mechanical Framework for Bulk and Frontal Polymerization: Coupled Kinetics and Front Stability
Xuanhe Li and Tal Cohen
Polymerization is a fundamental chemical process enabling large-scale production of material components across modern industries. By transforming a monomer mixture into a cross-linked
polymer network, polymerization induces changes in temperature and material properties such as density and stiffness, which can generate residual stress and warping through coupled mechanisms that remain incompletely understood. Depending on processing conditions, polymerization may occur either in the bulk, sustained by continuous external energy input, or as a self-sustaining exothermic reaction front, commonly referred to as frontal polymerization. While frontal polymerization offers rapid and energy-efficient curing, its localized reaction zone produces sharp spatial gradients that amplify thermo-chemo-mechanical coupling effects. In this work, we develop a thermodynamically consistent framework that captures both bulk and frontal polymerization, incorporating stress-dependent reaction kinetics and the
evolution of the stress-free configuration during curing. Using a narrow reaction-zone approximation in a uniaxial setting, we derive analytical predictions for propagation velocity, residual stress development, and stability. A perturbation analysis yields a stability criterion that generalizes the classical Zeldovich number by accounting for heat loss and mechanical loading, and enables construction of a phase diagram distinguishing stable, unstable, and quenched propagation regimes.
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Statistical Mechanics · Cross-listed from nlin.CD
The relation between classical and quantum Lyapunov exponent and the bound on chaos in classically chaotic quantum systems
Fabian Haneder, Gerrit Caspari, Juan Diego Urbina et al. (+1 more)
Out-of-Time-Ordered Commutators (OTOCs), representing a key diagnostic for scrambling as a facet of short-time
quantum chaos, have attracted wide-ranging interest, from many-body physics to
quantum gravity. By means of a suitable form of the Wigner-Moyal expansion, and invoking ensemble equivalence in statistical physics, we provide a consistent approach to the growth rate of the OTOC for many-body systems with chaotic classical limit where both the classical Lyapunov exponent and the
quantum nature of the density of states enter. Applying this construction to quantized high-dimensional
hyperbolic motion, i.e., a
quantum chaotic system that exhibits
gravity-like correlation functions in the late-time regime, we compute the OTOC growth rate $\Lambda$ as a function of the number of degrees of freedom, $f$, and inverse temperature, $\beta$. We show that the scaled growth rate, $\Lambda/f$, can be described by a universal function of $f \beta$ and displays a cross-over from classical to
quantum behavior as we increase $f$ and/or lower the temperature. In the deep
quantum regime of infinite $f$, we find maximally fast scrambling in the sense of the Maldacena-Shenker-Stanford bound on chaos. This elucidates the non-perturbative mechanism underlying the saturation of the bound via
quantum contributions to the mean density of states, and it provides further support for this dynamical system as a dual to two-dimensional
quantum gravity. In this way, we present first evidence of maximally fast scrambling in a
quantum chaotic system with a well-defined classical
Hamiltonian limit, without invoking any external mechanism such as (disorder) averaging.
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All authors Fabian Haneder, Gerrit Caspari, Juan Diego Urbina, Klaus Richter
Soft Condensed Matter
Dynamics of self-organization in dense persistent active matter
Atharva Shukla and Chandan Dasgupta
We consider a two-dimensional athermal binary mixture of Lennard-Jones particles with persistent random active forces. The
liquid phase of this system for active forces exceeding a threshold value exhibits self-organization with long-range spatial correlations of particle velocities and active forces. We study by simulations the development of these correlations from a random initial state. Several characteristics of the growth of correlations are measured and compared with those of phase-ordering kinetics of
equilibrium systems after a quench from a disordered state. The motion of the particles in the long-time steady state is found to be dominated by two streams that flow in opposite directions.
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Soft Condensed Matter
On the Role of Internal Degrees of Freedom in Structural Relaxation of Ring-Tail Structured Liquids Across Temperature Regimes
Rolf Zeißler, Sandra Krüger, Robin Horstmann et al. (+3 more)
We investigate how anisotropic molecular rotation and internal molecular flexibility influence
liquid dynamics in 1-phenylalkanes. To this end, we combine depolarized dynamic light scattering,
nuclear magnetic resonance spectroscopy and molecular dynamics simulations. Our results show that anisotropic rotations and internal molecular flexibility substantially contribute to structural relaxation in the
liquid state. However, their influence diminishes on entering the supercooled-
liquid regime, where the relaxation behavior develops towards the previously identified generic relaxation shape, likely due to the increasing cooperativity of rotational dynamics. Because 1-phenylalkanes are simple model systems with similarities to many other molecular
liquids, this study suggests that effects of anisotropic rotation and internal flexibility are relevant in various
liquids with similar molecular complexity, and provides a proof of concept for how these effects can be identified.
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All authors Rolf Zeißler, Sandra Krüger, Robin Horstmann, Till Böhmer, Michael Vogel, Thomas Blochowicz
Disordered Systems and Neural Networks · Cross-listed from quant-ph
Quantum information scrambling in strongly disordered Rydberg spin systems
Maximilian Müllenbach, Sebastian Geier, Adrian Braemer et al. (+5 more)
Despite the fact that power-law interactions occur in a plethora of physical systems, their many-body dynamics is far less understood than that of nearest-neighbor interacting systems. Here, we study information scrambling in strongly disordered
spin systems with power-law interactions via out-of-time-order correlators (OTOCs). Numerically, we find pronounced differences in the dynamical spreading of OTOCs between nearest-neighbor and power-law interacting systems. This deviation persists even for short-range interactions, opposing the common view that these interactions produce dynamics equivalent to the nearest-neighbor case. In a detailed experimental proposal, tailored but not limited to Rydberg tweezer setups, we present a protocol to extract OTOCs in XXZ Heisenberg
spin systems with tunable anisotropy and programmable disorder based on currently available techniques.
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All authors Maximilian Müllenbach, Sebastian Geier, Adrian Braemer, Eduard J. Braun, Titus Franz, Gerhard Zürn, Matthias Weidemüller, Martin Gärttner
Strongly Correlated Electrons
Bosonization solution of the Kondo lattice in a Luttinger liquid
Tomás Bortolin, C. J. Bolech, Nayana Shah et al. (+1 more)
We address the physics of a regular arrangement of independent
magnetic impurities embedded in a band of interacting electrons. We focus on the one-dimensional case that can be studied using bosonization and in which the electron bulk is described by a Luttinger
liquid. The
impurity spins interact with the electrons via
magnetic exchange that introduces the possibility of Kondo and Ruderman-Kittel-Kasuya-Yosida (RKKY) physics. We find that for two special values of the interactions, the model can be refermionized as a noninteracting electron band hybridized with a regular array of resonant levels. These solvable limits provide access to
impurity correlators that correspond to either extended algebraic order or local screening. A physical picture emerges of how the interelectron interactions can stabilize either Kondo or RKKY physics depending on the sign of the interaction.
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All authors Tomás Bortolin, C. J. Bolech, Nayana Shah, Aníbal Iucci
Mesoscale and Nanoscale Physics · Cross-listed from physics.optics
Designing low-loss cavities across the band-gap of photonic crystal slabs
Nadhia Monim, Wolfgang Langbein and Francesco Masia
Photonic
crystal cavities (PCCs) are defects in host photonic
crystals (PCs) which create bound states in the PC band gap. These bound states are resonant states of the electromagnetic field with a complex resonance frequency and can have very small mode volumes. PCCs are attractive for a variety of applications, from cavity
quantum electrodynamics to biosensing. A PC slab geometry is advantageous given its superior manufacturability compared to three-dimensional
crystals, and the accessibility of the surface allows sensing and coupling. However, the emission into the half spaces above and below the slab limits the bound state lifetime. Controlling this emission is thus crucial for applications, most of which benefiting from a long lifetime. A range of methods to find defect geometries suppressing the emission to increase the lifetime have been demonstrated in the past. However, they do not cater for a designed resonant frequency covering a wide addressable range, as needed for multiplexed devices. Here, we demonstrate a design method controlling both resonance frequency and emission, by minimising a cost function including both losses and target frequency. We show applications on PCCs in GaAs PC slabs immersed in water, relevant for biosensing. The reduced refractive index contrast in these structures compared to previously studied PCCs embedded in
vacuum renders the emission suppression more challenging. We optimize the quality factor of a standard L3 cavity from 1000 to 10^4-10^5, with an addressable resonance frequency range covering 12% relative bandwidth, spanning more than half of the band gap. We furthermore report optimised structures of H1 cavities, and provide the optimisation code for widespread use.
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Statistical Mechanics · Cross-listed from quant-ph
Fundamentals of quantum Boltzmann machine learning with visible and hidden units
Mark M. Wilde
One of the primary applications of classical Boltzmann machines is generative modeling, wherein the goal is to tune the parameters of a model distribution so that it closely approximates a target distribution. Training relies on estimating the gradient of the relative
entropy between the target and model distributions, a task that is well understood when the classical Boltzmann machine has both visible and hidden units. For some years now, it has been an obstacle to generalize this finding to
quantum state learning with
quantum Boltzmann machines that have both visible and hidden units. In this paper, I derive an analytical expression for the gradient of the
quantum relative
entropy between a target
quantum state and the reduced state of the visible units of a
quantum Boltzmann machine. Crucially, this expression is amenable to estimation on a
quantum computer, as it involves modular-flow-generated
unitary rotations reminiscent of those appearing in my prior work on rotated Petz recovery maps. This leads to a
quantum algorithm for gradient estimation in this setting. I then specialize the setting to
quantum visible units and classical hidden units, and vice versa; I also provide analytical expressions for the gradients, along with
quantum algorithms for estimating them. Finally, I replace the
quantum relative
entropy objective function with the Petz-Tsallis relative
entropy; here I develop an analytical expression for the gradient and sketch a
quantum algorithm for estimating it, as an application of an independent derivation of a formula for the derivative of the
matrix power function, which also involves modular-flow-generated
unitary rotations. Ultimately, this paper demarcates progress in training
quantum Boltzmann machines with visible and hidden units for generative modeling and
quantum state learning.
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Disordered Systems and Neural Networks
Spin Glasses: Disorder, Frustration, and Nonequilibrium Complexity
Naeimeh Tahriri, Vahid Mahdikhah, Jahanfar Abouie et al. (+1 more)
Spin glasses occupy a unique place in condensed matter: they freeze collectively while remaining struc-turally disordered, and they exhibit slow, history-dependent dynamics that reflect an exceptionally rug-ged free-energy landscape. This review provides an integrated account of
spin-glass physics, emphasiz-ing how microscopic ingredients (quenched randomness, frustration, competing exchange interactions, and random fields) conspire to produce macroscopic glassiness. We begin with the canonical Edwards-Anderson and Sherrington-Kirkpatrick formulations to introduce the central theoretical ideas that recur across the literature: extensive degeneracy, metastability, and the emergence of long relaxation times that manifest as aging,
memory, and rejuvenation under standard experimental protocols. We then summarize the principal routes used to characterize
spin-glass freezing, combining thermodynamic signatures with dynamical probes that reveal the separation of timescales and the sensitivity to thermal and
magnetic histories. Building on these foundations, we draw connections across experimental material classes (me-tallic
alloys, insulating
oxides, and geometrically frustrated systems) by emphasizing how intrinsic ver-sus induced disorder and competing interaction networks shape the observed phenomenology. Recent advances in reentrant and room-temperature
spin-glass materials are highlighted as a rapidly developing direction that tests the limits of established paradigms and motivates new materials-driven questions. The review concludes by connecting modern computational developments, including machine-learning phase identification and neural-network analogies, to longstanding challenges in classification, univer-sality, and out-of-
equilibrium behavior, and by outlining emerging opportunities at the boundary between classical and
quantum spin glasses.
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All authors Naeimeh Tahriri, Vahid Mahdikhah, Jahanfar Abouie, Daryoosh Vashaee
Strongly Correlated Electrons
Preparation of a Quantum Spin Liquid in Non-Hermitian Quantum Dimer Models and Rydberg Arrays
Shashwat Chakraborty and Taylor L. Hughes
We identify an unconventional form of the non-Hermitian skin effect that occurs not in position space but in many-body Fock space, which we call the Fock space skin effect (FSSE). Using
quantum dimer models, we characterize FSSE analytically and numerically, and propose a concrete route toward its realization in Rydberg atom arrays. The dimer constraint is enforced through Rydberg gadgets employing the blockade mechanism, while directional reservoirs generate non-Hermitian flipping amplitudes. We show that FSSE enables the preparation of gapped
spin liquid states, and in particular, we demonstrate how a Rydberg geometry realizing a square
lattice quantum dimer model with next-nearest neighbor dimers can be driven by non-Hermiticity into an exact
spin liquid ground state. Our results establish Fock-space non-Hermiticity as a powerful principle for engineering exotic
quantum phases and dynamical state-preparation protocols.
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Superconductivity
Quantum Phases of a Strongly Disordered Two-Legged Josephson Ladder
Eyal Walach and Efrat Shimshoni
Disordered
superconductors in low dimensions provide an exemplary manifestation for the role of
quantum fluctuations in a many-body system. Specifically in Josephson arrays with comparable Josephson and charging energies ($E_J\sim E_C$), disorder tends to change the nature of the paradigmatic
Superconductor-
Insulator Transition (SIT) and potentially leads to formation of multiple distinct phases. We address this problem in a model of a two-legged Josephson ladder subjected to a wide spatial distribution of its parameters along the legs. In contrast, we assume the system to have a perfect $\mathbb{Z}_2$
symmetry to interchange between the legs, and investigate the effects of spatial randomness which preserves this
symmetry in the strong-disorder limit. To this end, we apply a strong randomness real-space renormalization group technique and explore the resulting phase diagram. We identify three disorder-dominated phases, including an intermediate phase between a disordered
superconductor and a disordered
insulator. The latter insulating phase can be mapped to a XY
spin-chain in a
spin glass phase, while the intermediate phase turns out to be a Bose glass.
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Statistical Mechanics · Cross-listed from quant-ph
Ergotropy of quantum many-body scars
Zhaohui Zhi, Qingyun Qian, Jin-Guo Liu et al. (+1 more)
Quantum many-body scars break ergodicity and evade thermalization, resulting in sub-volume law
entanglement entropy even with high energy density. While their
quantum correlations and
entanglement have been elaborated previously, their capacity in storing extractable energy, quantified by the notion ergotropy, remains an open question. Here we focus on the representative PXP model, and unveil the extensive ergotropy scaling of a family of states interpolating between
quantum many-body scars and thermal states, the latter of which are known to be passive with vanishing ergotropy in the thermodynamic limit. A phenomenological relation between ergotropy and
entanglement is uncovered, which generalizes the existing free
fermion integrable results to an interacting scenario. The ergotropy in a dynamical protocol shows that a reset with a global uniform coherent rotation can inject extractable energy, as a proof of principle way to charge a
quantum "battery". Our protocol is tailored for near term Rydberg neutral atoms array, while also being feasible for other
quantum processors. Our results establish that
quantum many-body scars, despite the tiny fraction of the
Hilbert space they occupy, can be efficiently exploited for storing extractable energy, and "scarring" a many-body system as a promising route for engineering
quantum many-body battery.
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All authors Zhaohui Zhi, Qingyun Qian, Jin-Guo Liu, Guo-Yi Zhu
Strongly Correlated Electrons
All-to-All interactions via multifractal wavefunction geometry
YouYoung Joung, Jemin Park and SungBin Lee
We uncover a generic mechanism through which the intrinsic geometry of multifractal
quantum wavefunctions generates effective all-to-all interactions in many-body systems. By analyzing the multifractal spectrum, we demonstrate that the simultaneous participation of widely separated length scales creates a global connectivity that bypasses local interaction constraints. This nonlocality leads to fast information scrambling, evidenced by sharp changes in the quenched dynamics of the
quantum Fisher information and bipartite mutual information with the onset of negative tripartite mutual information. Such rapid scrambling is a defining feature of strongly chaotic
quantum dynamics, and our results identify the systems with multifractal states as a promising solid-state platform for realizing this regime. More broadly, they reveal a new paradigm in which complex, multiscale wavefunction structure intrinsically generates long-range connectivity, providing a natural route to achieving nonlocal behavior in strongly correlated
quantum materials.
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Mesoscale and Nanoscale Physics
Geometry-Enforced Topological Chiral Fermions in Amorphous Chiral Metals
Justin Schirmann, Adolfo G. Grushin and Benjamin J. Wieder
Since the prediction and observation of topological Weyl semimetals (
chiral TSMs), there have been enormous efforts to characterize further condensed matter realizations of
chiral fermions. These efforts were dramatically accelerated by the subsequent discovery of a profound link between low-energy topological and
lattice chirality in structurally
chiral crystals. Though TSMs are well understood in the limit of perfect translation
symmetry, real solid-state materials host defects and disorder, and may even be rendered amorphous down to all but the smallest system length scales. Previous theoretical studies have concluded that
chiral TSMs transition into trivial diffusive metals at moderate disorder scales, raising concerns that
chiral TSM states may only be accessible in highly crystalline samples. In this work, we in contrast identify large families of
chiral TSMs that instead persist under strong structural disorder even into the amorphous regime. We show that amorphous
chiral TSM phases can be stabilized in particular by the presence of long-range order in the local structural chirality. We present extensive analytic and numerical calculations demonstrating the existence of both Weyl and higher-charge
chiral fermions in amorphous metals whose
topology and
spin and orbital angular momentum textures are tunable via the interplay of average
symmetry and geometry. To distinguish and generate new realizations of strongly disordered
chiral fermions, we introduce an analytic approach grounded in
symmetry group theory. We then introduce an amorphous Wilson loop numerical method to identify
chiral fermions in metals with 3D structural disorder. Our findings bridge the crystalline and strongly disordered regimes of
chiral TSMs, and indicate a clear route toward engineering geometry-enforced
topology in noncrystalline materials and metamaterials.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Learning transitions of topological surface codes
Finn Eckstein, Bo Han, Simon Trebst et al. (+1 more)
For the surface code, topological
quantum order allows one to encode logical
quantum information in a robust, long-range entangled many-body
quantum state. However, if an observer probes this
quantum state by performing measurements on the underlying
qubits, thereby collecting an ensemble of highly correlated classical snapshots, two closely related questions arise: (i) do measurements decohere the topological order of the
quantum state; and (ii) how much of the logical information can one learn from the snapshots? Here we address these questions for measurements in a uniform basis on all
qubits. We find that for generic measurement angles, sufficiently far away from the Clifford X, Y, and Z directions (such as the X+Y+Z basis) the logical information is never lost in one of the following two ways: (i) for weak measurement, the topological order is absolutely robust; (ii) for projective measurement, the
quantum state inevitably collapses, but the logical
quantum information is faithfully transferred from the
quantum system to the observer in the form of a tomographically complete classical shadow. At these generic measurement angles and in the projective-measurement limit, the measurement ensemble enforced by Born probabilities can be represented by a 2D tensor network that can be fermionized into a disordered, free-
fermion network model in
symmetry class DIII, which gives rise to a Majorana "metal" phase. When the measurement angle is biased towards the X or Z limits, a critical angle indicates the threshold of a learning transition beyond which the classical shadow no longer reveals full tomographic information (but reduces to a measurement of the logical X or Z state). This learning transition can be described in the
language of the network model as a "metal to
insulator" transition...
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All authors Finn Eckstein, Bo Han, Simon Trebst, Guo-Yi Zhu
Mesoscale and Nanoscale Physics
Micromagnet-free operation of electron spin qubits in Si/Si$_{1-x}$Ge$_x$ vertical double quantum dots
Abhikbrata Sarkar and Daniel Loss
We study a vertical double
quantum dot (DQD) in a Si/Si$_{1-x}$Ge$_x$/Si double-well
heterostructure for full electrical control of electron Loss-DiVincenzo (LD)
spin qubits, using realistic device modeling and numerical simulations. Due to the emerging
spin-orbit interaction in the DQD, as well as strain from the gate electrodes, small (percentage range) but finite $g$ tensor variations emerge. In addition, we find a large valley splitting, on the order of $E_v{\sim}250\,\mu$eV. As a result, multiple avenues for fast electrical single
qubit rotations emerge. An ac electric field gives rise to electric dipole
spin resonance (EDSR), while electron
spin resonance (ESR) in the presence of an ac
magnetic field can be electrically controlled by local gates due to varying $g$ factors in DQDs. We also show that shuttling between neighboring dots, in vertical and horizontal direction, results in ultrafast single
qubit gates of less than a nanosecond. Remarkably, this DQD architecture completely eliminates the need for micromagnets, significantly facilitating the scalability of LD
spin qubits in
semiconductor foundries.
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Disordered Systems and Neural Networks · Cross-listed from quant-ph
Theory of Scalable Spin Squeezing with Disordered Quantum Dipoles
Avi Kaplan-Lipkin, Philip J. D. Crowley, Jonathan N. Hallén et al. (+6 more)
Spin squeezed
entanglement enables metrological precision beyond the classical limit. Understood through the lens of continuous
symmetry breaking, dipolar
spin systems exhibit the remarkable ability to generate
spin squeezing via their intrinsic quench dynamics. To date, this understanding has primarily focused on
lattice spin systems; in practice however, dipolar
spin systems$\unicode{x2014}$ranging from ultracold molecules to
nuclear spin ensembles and solid-state color centers$\unicode{x2014}$often exhibit significant amounts of positional disorder. Here, we develop a theory for scalable
spin squeezing in a two-dimensional randomly diluted
lattice of
quantum dipoles, which naturally realize a dipolar XXZ model. Via extensive
quantum Monte Carlo simulations, we map out the phase diagram for finite-temperature XY order, and by extension scalable
spin squeezing, as a function of both disorder and Ising anisotropy. As the disorder increases, we find that scalable
spin squeezing survives only near the Heisenberg point. We show that this behavior is due to the presence of rare tightly-coupled dimers, which effectively heat the system post-quench. In the case of strongly-interacting nitrogen-vacancy centers in diamond, we demonstrate that an experimentally feasible strategy to decouple the problematic dimers from the dynamics is sufficient to enable scalable
spin squeezing.
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All authors Avi Kaplan-Lipkin, Philip J. D. Crowley, Jonathan N. Hallén, Zilin Wang, Weijie Wu, Sabrina Chern, Chris R. Laumann, Lode Pollet, Norman Y. Yao
Materials Science · Cross-listed from physics.chem-ph
Validation of Quantum Computing for Transition Metal Oxide-based Automotive Catalysis
Yuntao Gu, Louis Hector Jr, Paolo Giusto et al. (+4 more)
Quantum computing presents a promising alternative to classical computational methods for modeling strongly correlated materials with partially filled d orbitals. In this study, we perform a comprehensive
quantum resource estimation using
quantum phase estimation (QPE) and qubitization techniques for transition metal
oxide molecules and a Pd zeolite catalyst fragment. Using the binary
oxide molecules TiO, MnO, and FeO, we validate our active space selection and benchmarking methodology, employing classical multireference methods such as complete active space self-consistent field (CASSCF) and N-electron valence state perturbation theory (NEVPT2). We then apply these methods to estimate the
quantum resources required for a full-scale
quantum simulation of a $Z_2Pd$ ($Z=Al_2Si_{22}O_{48}$) fragment taken from the $Pd/2(Al_xSi_{(1-x)})$ catalyst family where x=Si/Al. Our analysis demonstrates that for large Pd zeolite systems, simulations achieving chemical accuracy would require ~$10^6-10^7$ physical
qubits, and range that is consistent with the projected capabilities of future fault-tolerant
quantum devices. We further explore the impact of active space size, basis set quality, and phase estimation error on the required
qubit and gate counts. These findings provide a roadmap for near-term and future
quantum simulations of industrially relevant catalytic materials, offering insights into the feasibility and scaling of
quantum chemistry applications in materials science.
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All authors Yuntao Gu, Louis Hector Jr, Paolo Giusto, Matthew Titsworth, Alok Warey, Dnyanesh Rajpathak, Eser Atesoglu
Mesoscale and Nanoscale Physics · Cross-listed from physics.chem-ph
Rapid reduction of nitrophenols using reusable magnetic h-BN/Ni–NiO nanocomposites
Anjali Varshney, Ritesh Dubey, Sushil Kumar et al. (+2 more)
The efficient and cost-effective conversion of nitro compounds to amines is crucial for industrial processes and environmental remediation, highlighting the growing demand for earth-abundant metal-based catalysts. In this study,
magnetic Ni–NiO nanostructures and their composites with two-dimensional hexagonal boron nitride (h-BN) were synthesized via a simple and scalable combustion method. The structural, morphological, and compositional properties of the synthesized materials were systematically investigated using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–Vis spectroscopy. The catalytic activity of both Ni–NiO and h-BN/Ni–NiO nanostructures was evaluated using nitrophenol reduction as a model reaction. The h-BN/Ni–NiO nanocomposite exhibited significantly enhanced catalytic performance compared to pristine Ni–NiO, highlighting the synergistic interaction between h-BN and Ni–NiO nanoparticles. Notably, the
magnetic nature of the Ni–NiO core enabled facile recovery of the catalyst using an external
magnetic field, and the composite demonstrated excellent stability and reusability for up to six catalytic cycles with minimal loss of activity. The combination of high catalytic efficiency,
magnetic separability, and structural stability positions the h-BN/Ni–NiO nanocomposite as a promising candidate for green and sustainable catalytic applications, particularly in environmental remediation.
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All authors Anjali Varshney, Ritesh Dubey, Sushil Kumar, Tapas Goswami, Samar Layek