General Relativity and Quantum Cosmology
Aliasghar Parvizi and Tomasz Pawłowski
Modifications to the dispersion relation of electromagnetic (EM) waves are a central probe in the search for
quantum gravitational effects. In this work, we construct a general framework for the interaction between the EM field and a
quantum background geometry, employing an extended Born-Oppenheimer approximation. This leads to a quasi-phenomenological model for EM wave propagation in curved spacetime. Unlike previous semi-classical approaches for mode-dependent dispersion relations, our framework naturally reproduces chromatic dispersion effects analogous to those observed in light-matter interactions in nonlinear optics. As a concrete application, we analyze EM wave propagation on a flat
quantum Friedmann-Lemaitre-Robertson-Walker (FLRW) background, combining analytical techniques with numerical simulations to extract observable signatures of the prism-like behavior induced by
quantum light-geometry interactions. Crucially, it remains valid across all energy regimes, enabling access to
quantum gravitational corrections beyond the semi-classical limit.
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Cosmology and Nongalactic Astrophysics
Model-Independent Indication for a Localized Anomaly in the Late-Time Expansion History
Shibendu Gupta Choudhury, Purba Mukherjee, Eleonora Di Valentino et al. (+1 more)
We investigate the late-time expansion history of the Universe using a model-independent spline reconstruction of cosmological distances based on the latest DESI DR2
baryon acoustic oscillation (BAO) measurements and the DES Dovekie Type Ia
supernova compilation. Comparing the reconstructed expansion history with the prediction of the Planck 2018 $\Lambda$CDM model, we identify a localized deviation over the
redshift interval $0.3\lesssim z\lesssim0.6$, reaching a maximum significance of approximately $3.5\sigma$ at $z\simeq0.47$. We demonstrate that this feature persists under substantial variations of the reconstruction methodology,
dataset composition and sound-horizon calibration. Mock analyses further show that the reconstruction is unbiased and that the observed anomaly is unlikely to arise from reconstruction bias or miscalibrated uncertainties. If confirmed by future observations, this localized feature could point to previously unrecognized late-time physics or reveal subtle inconsistencies between early and late Universe cosmological probes.
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All authors Shibendu Gupta Choudhury, Purba Mukherjee, Eleonora Di Valentino, Anjan A Sen
Atomic Physics
High-fidelity entanglement of polar molecules by dynamic geometric control
Scarlett S. Yu, Avikar Periwal, Jiaqi You et al. (+6 more)
In
quantum information systems made of optical tweezer arrays of ultracold molecules, thermal motion of molecules degrades the coherence of their interactions, which limits
entanglement fidelity and the concomitant scientific applicability of these systems. We show that by controlling the geometry of the dipolar interaction, even when a molecule occupies many motional states in the tweezer, coherence can be preserved. We characterize several geometries that suppress sensitivity to thermal fluctuations. We further use programmable, coherence-preserving motion of the molecules during
entanglement to refocus dephasing from relative positional jitter of the tweezers, which is relevant even on the 10 nm scale. These methods yield substantially improved dipolar coherence and enable generation of two-molecule
entanglement with a Bell state fidelity of $\mathcal{F}= 0.976^{+0.008}_{-0.011}$ in directly
laser-cooled molecules.
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All authors Scarlett S. Yu, Avikar Periwal, Jiaqi You, Zirui Liu, Qinshu Lyu, Youngju Cho, Loïc Anderegg, Eunmi Chae, John M. Doyle
Astrophysics of Galaxies
Alignment of the Milky Way and M31 with their cosmic environment. New insights from constrained Local Group simulations
Hanneke C. Woudenberg, Amina Helmi, Ewoud Wempe et al. (+4 more)
The large-scale environment is thought to play an important role in setting
galaxy properties. The Milky Way (MW) and Andromeda (M31) reside in the Local Group, embedded in the Local Sheet (LS). To study the sheet's influence on the dark matter (DM)
halo shapes,
spins, and disks orientations of MW and M31 analogues, we use a new suite of constrained Local Group simulations that reproduce the observed configuration of the two main
halos and the LS. We determine their shapes and
alignments relative to the LS analogues, and the effect of infall and coalescence of massive mergers. We find that the DM
halo shapes of our MW and M31 analogues are on average slightly rounder than literature reports for similar-mass
galaxies in random environments. We find preferential
alignment between the sheet normal and the
halos' minor axes, but not with the
halos'
spins. The present-day disk angular momenta ($L_{\rm disk}$) closely align with the
halos' minor axes (median $15^{+15}_{-8}$ degrees at $R_{\rm vir}$) and with the
halos'
spins. The direction of $L_{\rm disk}$ is often set by one of the two highest mass ratio mergers during the last 8-10 Gyr. While recent ($\leq 2$ Gyr) massive mergers can reorient the outer
halo's minor axis leading to twisted shapes, $L_{\rm disk}$ retains the imprint of the earlier
accretion event. These results can explain the peculiar
alignment of the MW's disk and DM
halo shape and their orientation relative to the LS. The prolate-like morphology and orientation of the MW's outer
halo can be explained by the Magellanic Clouds (and perhaps Sagittarius) accreting from within the LS. As their orbital planes are nearly perpendicular to the
Galactic disk, the disk orientation must be set earlier, possibly by the GES merger. This merger's estimated infall direction, highly inclined relative to the present-day LS, is broadly consistent with the LS's direction of maximum collapse.
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All authors Hanneke C. Woudenberg, Amina Helmi, Ewoud Wempe, Anna Genina, Simon D.M. White, Jens Jasche, Guilhem Lavaux
Instrumentation and Methods for Astrophysics
picoMUX: microcontroller based time-domain multiplexing readout for kilopixel TES arrays
Simon Tartakovsky, Alexandre E. Adler, Jason E. Austermann et al. (+23 more)
Advances in cryogenic SQUID-based time-domain multiplexing (TDM) have outpaced their warm readout electronics. Next generation CMB
telescopes are baselining kilopixel TES arrays with few viable electronic options. We present picoMUX, a new TDM readout electronics architecture that replaces the FPGA typically used in such systems with a complement of modern microcontrollers. Designed around the current generation NIST multiplexer, it fully exploits its differential nature and two-level switching. The system achieves the desired timing metrics (sub {\mu}s row dwell time) while reducing cost, complexity, and power consumption over a comparable FPGA solution. Preliminary noise measurements are consistent with expectations and show no evidence that the novel architecture introduces excess noise. picoMUX demonstrates how recent advances in microcontrollers enable simpler, low-power, low-cost TDM readouts for kilopixel TES arrays.
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All authors Simon Tartakovsky, Alexandre E. Adler, Jason E. Austermann, Steven J. Benton, Shannon M. Duff, Malcolm Durkin, Jeffrey P. Filippini, Aurelien A. Fraisse, Thomas J.L.J. Gascard, Sho M. Gibbs, Suren Gourapura, Jon E. Gudmundsson, Johannes Hubmayr, William C. Jones, Ashesh Khatua, Jared L. May, Darby McCauley, Johanna M. Nagy, Ivan L. Padilla, Ricardo R. Rodriguez, John E. Ruhl, M. Shaaf Sarwar, Christopher Rooney, Joseph van der List, Michael R. Vissers, Philippe Voyer
High Energy Physics (Theory)
The Infraparticle Edge
Soo-Jong Rey
I derive the charged-particle spectral edge from the
quantum instrument of soft QED. I use two projections of that instrument. Tracing over unresolved
photons gives the reduced hard-sector channel. Pushing the outcomes to total energy gives the inclusive energy distribution. Its Laplace exponent is fixed by the diagonal soft intensity. For ${\rm d} N_h(\omega)=\eta_h{\rm d}\omega/\omega+{\rm d} N_{h,\mathrm{reg}}(\omega)$, I obtain $\rho_{\mathrm{inc}}(s)\sim C\theta(s-m^2)(s-m^2)^{-1+\eta_h}$. I retain the coherence kernel and derive hard-sector dephasing and the spectral edge from two contractions of one soft environment. The diagonal coefficient $\kappa_{aa}$ fixes the endpoint exponent, while $\frac12(\kappa_{aa}+\kappa_{bb}-2\operatorname{Re}\kappa_{ba})$ fixes the dephasing exponent between hard alternatives. I then classify infrared energy marginals, derive the finite-resolution residue $Z(\mu)=(\mu/\Lambda)^{\eta_h}$, prove stability under infrared-integrable perturbations, and separate the bath exponent from a hard threshold exponent. For the one-electron spectral measure, the hard threshold factor is regular. The resulting edge has the local power law of a gapped unparticle spectrum, while its exponent remains a response coefficient of the unresolved
photon sector.
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Quantum Physics
Spin Chain Quantum Communication on a Trapped-Ion Processor
Madhumita Sarkar, Trinity Pointon and Sougato Bose
Efficient communication between distant
qubits is one of the central challenges in scaling
quantum processors. Although engineered
spin chain protocols have been extensively investigated theoretically, their experimental realization has remained comparatively limited. Here, we experimentally realize engineered
quantum communication protocols through digitally simulated
spin Hamiltonian on IonQ's Forte 1/ Forte Enterprise 1 trapped-ion
quantum processor. Combining exact numerical simulations with
quantum hardware experiments, we
benchmark uniform nearest-neighbour and engineered coupling profiles and demonstrate that engineered interactions significantly enhance the fidelity of
quantum state transfer. We further show that exploiting the commutation structure of the
spin Hamiltonian enables a parallel Trotter decomposition that more faithfully reproduces the target dynamics while substantially reducing the
circuit depth and execution time compared to the conventional sequential implementations. Our results demonstrate that programmable
quantum processors can effectively realize and efficiently implement
quantum communication protocols, bringing
Hamiltonian-based
quantum communication closer to practical
quantum technologies.
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Medical Physics
Reconstruction-Independent Resolution Limits in Preclinical Cone-Beam Micro-CT: A Closed-Form Analysis
Falk L. Wiegmann and Nancy L. Ford
Spatial resolution in preclinical cone-beam micro-CT is bounded by two reconstruction-independent limits, a
photon-noise limit from the projection-domain signal-known-exactly, background-known-exactly (SKE/BKE) ideal observer with the Rose criterion, and an angular-sampling limit from the Crowther criterion. The
photon-noise bound is a property of the input data and applies to any reconstruction
algorithm. The angular-sampling bound applies to classical analytic and iterative reconstructions (FDK, FBP, SIRT) that do not inject signal priors. We derive both limits in closed form for a circular feature in a uniform background, including an off-axis fan-beam extension, and combine them into a spatially varying effective resolution map. The combined limit yields a closed-form scan-design optimum. The maximum worst-case spatial frequency scales as the cube root of the total
photon budget per detector pixel (per-view flux times number of views), and an analytic rule sets how to split that budget between flux and views. We illustrate the framework on a representative preclinical micro-CT scanner, with parametric sweeps over flux and projection count that show how each acquisition parameter reshapes the resolution map. An accompanying open-source web calculator implements these bounds for arbitrary scanner geometries.
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Materials Science
Surface Phase-Field-Crystal-Helfrich model for out-of-plane deformations in thin crystalline sheets with lattice mismatch
Emma Radice, Ingo Nitschke, Marco Salvalaglio et al. (+1 more)
Thin, flexible crystalline sheets exhibit unique elastic properties due to their ability to undergo out-of-plane deformations. Understanding this behavior requires a description that couples in-plane elasticity, out-of-plane deformation, and their coupling, taking the crystalline structure and its defects into account. We develop a multiscale description for these systems by extending the surface Phase-Field-
Crystal-Helfrich model. The extension permits a spatially varying
equilibrium lattice spacing, enabling the representation of localized
lattice eigenstrain to mimic
lattice mismatch in
heterostructures. We validate the extended model against analytical predictions from classical Föppl-von Kármán equations for uniaxial compression and from Eshelby's inclusion problem. Using this validated framework, we then show how locally induced compressive stresses drive out-of-plane deformation in the sheets.
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All authors Emma Radice, Ingo Nitschke, Marco Salvalaglio, Axel Voigt
Quantum Physics
Expressibility and trainability of a two-dimensional pairwise quantum-circuit ansatz
Shuai Zhang, Wei Liu and Ji-Chong Yang
Parameterized
quantum circuits~(PQCs) constitute a central building block of variational
quantum algorithms~(VQAs) and
quantum machine learning~(QML) methods. Existing ansatz designs often adopt hardware-agnostic or simplified 1D chain/ring
entanglement patterns. However, as
quantum hardware continues to develop, native 2D connectivity patterns, such as planar superconducting-
qubit architectures, are becoming increasingly important. Inspired by this hardware structure, we construct a native 2D pairwise ansatz and compare its expressibility and trainability with representative 1D ansatze at identical layer depths, despite their different
circuit depths. For the fixed 16-
qubit system, the 2D ansatz has the smallest KL divergence at $L=1$ and $2$, and its second-order frame potential approaches the theoretical lower bound more rapidly at shallow layer counts than the frame potentials of the three 1D ansatze. We also evaluate the gradient variance of the Pauli-$Z$-string expectation value $\langle Z_0\otimes\cdots\otimes Z_{15}\rangle$ with respect to the first $R_y$ angle. For this Pauli-$Z$ string and fixed parameter, the gradient variance is smaller for the 2D
circuit at $L=1$–$4$. The differences narrow at $L=5$, and the four ansatze yield statistically compatible variances at $L=6$.
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Chaotic Dynamics · Cross-listed from cs.CG
One Shot, Twenty-One Balls: A Computer-Assisted Proof of a Single-Stroke Total Clearance in an Idealized Model of Snooker
Avner Kantor
Snooker folklore holds that no single stroke can pocket all twenty-one object balls. We examine the claim in an explicit model: twenty-two equal disks on a rectangle with six pocket points, under constant rolling deceleration, frictionless collisions with normal restitution, and lossy specular cushions. We exhibit a configuration and a stroke, and prove in interval arithmetic that every stroke in an explicit box around it pockets all twenty-one object balls, so the set of successful strokes has positive measure. That set is a ribbon: every speed from 9.3213 to 12 m/s works, while the certified window of directions is 9.4813e-43 radians wide, a number explained by a first-order analysis of twenty near-grazing collisions. A second configuration, a near-frozen cluster, has a certified window 9.4e-4 radians wide, thirty-nine orders of magnitude wider; its certificate uses Taylor models of degree six. The strokes with a given list of events form a semialgebraic set, and the endpoints of the windows are algebraic numbers. For the regulation opening position we state the corresponding
conjecture, and show that if it holds with a regular witness then a finite certified search establishes it.
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Quantum Physics
Fixed-Boost Wigner Noise: Strict Trace-Distance Contraction without Quantum Degradability
Maxim V. Churilov
A Lorentz boost acts on the canonical
spin of a massive particle through a momentum-dependent Wigner rotation. We show that, for one fixed observer boost, reducing over an uncertain momentum can strictly contract every pairwise
spin-state trace distance without producing a channel that is degradable from the less contracted one. For
spin $1/2$, we first characterize the exact inversion-symmetric channel cone generated by a fixed Wigner angle and transverse momentum directions. Inside this cone lies the Pauli family $M_\alpha=\operatorname{diag}(1-\alpha,1-\alpha,1-2\alpha)$, $0\leq\alpha<1/2$. For $0<\alpha<\beta<1/2$, all trace distances between distinct
spin states are strictly smaller after $M_\beta$ than after $M_\alpha$, yet the unique linear post-processing factor has a negative normalized Choi
eigenvalue. We solve the optimization over all physical converters exactly: $\frac{1}{2}\inf_{\Lambda\in\mathrm{CPTP}}\|\Phi_\beta-\Lambda\circ\Phi_\alpha\|_\diamond=\frac{\alpha(\beta-\alpha)}{2-3\alpha}$, whereas the reverse deficiency is $\beta-\alpha$. Thus the identity dominates the family, while all positive-noise members are pairwise incomparable under CPTP post-processing. The ideal construction is realized as the narrow-packet limit of pure, normalizable five-component momentum states, and explicit perturbation and finite-shot
tomography bounds certify an open set of examples. Separately, every nonidentity member fails
embedding in a time-homogeneous Pauli-diagonal Lindblad
semigroup. Hence ordering all unassisted
spin distinguishabilities does not determine the
quantum statistical post-processing order.
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Quantum Physics
A Noise-Aware Quantum Algorithm for Credit Valuation Adjustments on Real Quantum Hardware
Guillem Borràs Espert, Francisco Gómez Casanova, Luis de Pedro Sánchez et al. (+2 more)
Credit Valuation Adjustment (CVA) requires repeated risk-neutral expectation estimation, making it a natural test bed for
quantum amplitude estimation, whose coherent amplification can in principle reduce Monte Carlo sampling cost. Whether this advantage survives realistic financial encoding and noisy hardware remains open. We develop an end-to-end, noise-aware
quantum workflow for CVA, covering
market calibration, discretisation, oracle construction, hardware execution and error-budget analysis. The model combines a correlated two-asset exposure with discount and default factors, encoded through a QCBM-based joint time-
market distribution and controlled payoff rotations. We introduce contrast-aware
Bayesian iterative
quantum amplitude estimation (CABIQAE), which incorporates experimentally calibrated Grover-contrast loss into
Bayesian inference and
circuit-depth selection. Hardware-calibrated experiments show that CABIQAE exploits the limited amplification available on current devices more effectively than noise-agnostic alternatives and achieves a much lower classical post-processing runtime than the noise-aware BAE baseline. The analysis further decomposes the total CVA error into statistical, encoding, discretisation and hardware contributions. The full CVA oracle remains limited by
circuit depth and discretisation resolution.
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All authors Guillem Borràs Espert, Francisco Gómez Casanova, Luis de Pedro Sánchez, Senaida Hernández Santana, Pablo Serrano Molinero
High Energy Physics (Theory)
Enhanced Correlations in Hawking Radiation from Near-Extremal Collapse
Suzanne Bintanja, Seolhwa Kim and Per Kraus
We consider the formation of a near-extremal Reissner-Nordstrom black hole by collapse, and show how to compute correlations in the outgoing Hawking radiation due to enhanced gravitational backreaction effects in the near-horizon region. This is done by reducing to the s-wave and employing the
Hamiltonian formulation of Einstein-Maxwell theory coupled to a scalar field. Solving the constraints yields an action for the scalar field that incorporates gravitational backreaction effects at the
quantum level, governed by an effective coupling g = G/(\pi r_0^3 T_H) that grows at low temperature, as in recent Schwarzian-based analyses. This action produces corrections to the free field Hawking state which are imprinted on correlation functions of the Hawking radiation measured at null infinity. As part of our analysis, we show that this action evaluated in the AdS_2 region is equivalent, at the level of all tree-level boundary correlators, to the standard JT/Schwarzian description coupled to dressed bilocal operators. We also reproduce some one-loop results. In our approach, metric fluctuations are included
quantum mechanically through the reduced scalar action, rather than through a semiclassical expectation value, and our computation of the radiation manifestly reduces to Hawking's original treatment when metric fluctuations are neglected.
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Atomic Physics
A cryogenic neutral-atom platform with full optical access and 2-hour trap lifetime
Akhil Kumar, Lorenzo Festa, Avishay Grinberg et al. (+10 more)
Neutral-atom
quantum processors are rapidly scaling toward system sizes of more than ten thousand
qubits, allowing for the realization of a new class of
quantum computing
algorithms and
quantum simulation experiments. However, current neutral-atom platforms generally have to find a compromise between the optical accessibility and the storage time of atoms in optical potentials, limiting the available
qubit numbers. Here we report on the operation of a novel, cryogenically enhanced, neutral-atom apparatus that overcomes these apparently conflicting requirements. We demonstrate
vacuum-limited trapping lifetimes of up to two hours of single $^{88}\mathrm{Sr}$ atoms in an optical tweezer array while preserving full optical access and without the need for complex cryogenic enclosures. Our measurements show that exceptionally long single-atom lifetimes can be achieved with a relatively simple cryostat design. Our architecture can be straightforwardly ported to other atomic species and shows a viable path for scaling up to sorted arrays of tens of thousands of atoms.
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All authors Akhil Kumar, Lorenzo Festa, Avishay Grinberg, Eran Reches, Dimitrios Tsevas, Kevin P. Mours, Zhao Zhang, Robin Eberhard, Sebastian Blatt, Andrea Alberti, Johannes Zeiher, Immanuel Bloch, Max Melchner
Plasma Physics
Single-Shot High-Energy Muon and Particle Radiography with a Multi-GeV Laser-Wakefield-Accelerator-Driven Source
Kaixin Zhu, G. Jackson Williams, Roberto Versaci et al. (+29 more)
We report the first demonstration of single-shot particle radiography using a 1-10 GeV
laser-wakefield-generated beam of
muons, pions, and
neutrons. The test objects were imaged ~15 m from the beam source, through dense lead shielding followed by the walls of a building and a truck. The
muon content of the beam was directly confirmed using large volume scintillator-based detectors, which recorded particle decay events with timing delays consistent with the
muon lifetime. Simulations confirm that the high energy component of the beam transmitted through the test object is nearly entirely composed of
muons, directly showing their highly penetrative nature, with a single-shot fluence equivalent to >8 hours of integration of
cosmic ray
muons near the horizon. Our work establishes single-shot high-energy particle radiography with a
laser-wakefield-accelerator-driven source.
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All authors Kaixin Zhu, G. Jackson Williams, Roberto Versaci, Ela Rockafellow, Anna Cimmino, Jaron E. Shrock, Reed Hollinger, Gabriele M. Grittani, Jiří Šišma, Ari Sloss, Nikola Durand, Nischal Tripathi, Jay Jablonski, James King, Gerardo Palma, Zach Rautio, Bryan Sullivan, Shoujun Wang, Frederica Sorkin, Sina Zahedpour, Ping Zhang, Bo Miao, Andrew Yandow, Mayank Gupta, Scott W. Hancock, Scott C. Wilks, Vincent Tang, David Warner, Jorge J. Rocca, John Harton, Howard M. Milchberg, Brendan A. Reagan
Quantum Physics
The log log jam in Gaussian state tomography
Sitan Chen, Weiyuan Gong, Qi Ye et al. (+1 more)
Unlike in finite dimensions,
quantum information in continuous-variable systems has the peculiar feature that without imposing physical constraints, the sample complexity of state
tomography can be unbounded. Remarkably, this is even the case for state-of-the-art protocols for learning Gaussian states, which have finite-dimensional descriptions: the best known rates scale with $\log \log E$, where $E$ is the energy of the system. We prove this is not an artifact of existing analyses, but a fundamental limitation of the measurements used. We show: (1) Any protocol that uses Gaussian measurements, even entangled or adaptively chosen ones, must incur a $\log \log E$ dependence. This answers an open question posed by a number of previous works. (2) There is a smooth tradeoff between the number of rounds of adaptivity and the energy dependence, and we give a matching protocol achieving this interpolated rate. (3) With highly entangled, non-Gaussian measurements, one can learn $n$-mode pure Gaussian states with $O(n^2 / \epsilon^2)$ samples, independent of $E$. This answers an open question posed by Chen et al. (4) A simple protocol based on the single-copy canonical phase POVM of Holevo and Helstrom learns single-mode pure Gaussian states with $O(1/\epsilon^2)$ samples, again independent of $E$. Our results clarify the role of energy in bosonic state
tomography and shed new light on the intriguing interplay between adaptivity,
entanglement, and magic in
quantum learning.
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All authors Sitan Chen, Weiyuan Gong, Qi Ye, Zhihan Zhang
Quantum Physics
An Agentic Formalization for Certified Quantum Neural Network Design
Mingrui Jing, Lei Zhang, Yusheng Zhao et al. (+2 more)
A central model in
quantum machine learning is the
quantum neural network (QNN), whose design requires balancing expressivity and trainability. Technically, expressivity is studied through
circuit-function analysis, such as
quantum signal processing, while trainability is analyzed using dynamical-Lie-
algebra (DLA) methods. To support certified QNN design, we formalize these major components of QNN theory in a connected lean 4 development checked by a proof kernel, where every analytic input is either proved or exposed as a named hypothesis. On the expressivity side, we prove exact if-and-only-if characterizations of single-
qubit QNNs, a resource-counted
quantum phase processing
theorem, and an overparameterization ceiling that bounds the
quantum Fisher information rank by the DLA dimension. On the trainability side, we derive the direct-sum loss-variance law through a de-circularized second-moment interface. A parameterized Casimir-uniqueness engine discharges the required inputs for fully controllable, orthogonal, and matchgate
circuit families, while single-
qubit and product-Clifford ensembles close the two-design assumptions directly. A capstone
theorem pairs the conditional variance law with exact loss reconstruction in DLA coordinates. The development record identifies eight corrections and clarifications that were not explicit in the informal arguments. We expect this work to provide a machine-checkable foundation for QNN theory and a step toward AI-assisted or automated design of
quantum machine learning
algorithms.
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All authors Mingrui Jing, Lei Zhang, Yusheng Zhao, Hongshun Yao, Xin Wang
Chemical Physics · Cross-listed from cs.HC
Sensing the properties of virtual objects without physical feedback
Rhoslyn Roebuck Williams, Harry J. Stroud, Luis E. Toledo et al. (+2 more)
People who have interacted with simulated worlds and simulated objects in extended reality (XR) often have a sense that they can 'feel' the objects being simulated despite them not being physical. Our sense of touch is essential for how we 'feel' the physical world, however, there is an open question as to what it means to 'feel' virtual objects when interacting with them in immersive digital environments. In prior research, we have reported that participants often describe a subjective experience of 'feeling' the properties of simulated molecular objects while using interactive molecular dynamics in extended reality (iMD-XR), a field-based interaction paradigm for manipulating real-time simulations of molecular objects without haptic feedback. To better understand these subjective reports of 'feeling', we used a psychophysics approach to quantify the threshold at which participants perceive differences in the
rigidity of simulated molecular objects (C$_{60}$ molecules) in iMD-XR. To evaluate this, we carried out experiments to compare the just-noticeable differences (JNDs) in two conditions: (1) via direct interaction with a real-time C$_{60}$ simulation, and (2) via observation-only$\unicode{x2013}$i.e. watching another person interacting with the simulations. Our findings show that direct interaction enabled participants to perceive more subtle
rigidity differences of 11.5%, compared to 18.5% for observation-only. Furthermore, participants who undertook interaction first were better able to distinguish
rigidity differences in the subsequent observation-only condition, suggesting that interaction trained participants to better perceive differences in molecular properties. These findings demonstrate a novel and flexible approach for sensing the properties of virtual objects in XR, and offer new insights into iMD-XR's potential in molecular research and education.
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All authors Rhoslyn Roebuck Williams, Harry J. Stroud, Luis E. Toledo, Mark D. Wonnacott, David R. Glowacki
High Energy Physics (Theory)
Causality and realizability of local operations in quantum field theory
Jan Mandrysch, Robin Simmons and Miguel Navascues
As noted by Sorkin, regarding
quantum instruments whose Kraus operators are localizable within some spacetime region as operations accessible therein leads to superluminal communication. This so-called Sorkin paradox can be resolved by further constraining the set of allowed local operations in
quantum field theory (QFT). In this spirit, Fewster and Verch proposed a framework for local QFT operations that generalizes non-relativistic
quantum measurement theory and does not lead to Sorkin-like paradoxes. Shortly afterwards, Jubb (and later Oeckl) identified the minimal conditions that QFT instruments must satisfy to be compatible with Einstein's causality. In this work, we study both approaches in the
quantum field theory of the free scalar field. First, we prove that a very wide class of causal instruments is FV-realizable: namely, those whose measurement channels are random displacements of the field operators. As we show, this class allows implementing arbitrary instruments in a heralded, probabilistic way, as well as non-demolition measurements deterministically. Second, we construct examples of causal channels that do not admit an approximate FV realization. Some of such causal, not FV-realizable channels violate basic physical principles, so they should not be part of any measurement theory for QFT. Third, we investigate the difficulty of characterizing the set of QFT channels that can be generated through the composition of several FV schemes. In this regard, we find a countable family of simple QFT channels for which no Turing machine can discriminate between channels within or far away from the implementable set.
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Cosmology and Nongalactic Astrophysics
Models with Non-minimal Coupling in Primordial Universe and Cosmological Observations
Alireza Talebian, Hassan Firouzjahi and Fereshteh Felegary
A non-minimal coupling between
gravity and the inflaton field is a generic contribution in inflationary cosmology. In this work, we consider models of inflation with a non-minimal coupling $-\xi\phi^2 R$ and study their observational predictions for the tensor-to-scalar ratio $r$ and the spectral index $n_s$. Unlike the conventional approach of working in the Einstein frame, we perform the analysis in the Jordan frame where the underlying dynamics, particularly the competition between the potential force and the coupling-induced friction, are more transparent. For suitable values of $\xi$, the system exhibits an extended constant-roll regime, in which this friction counteracts the potential force. Focusing on monomial potentials $V(\phi) \propto \phi^n$, we find that negative $\xi$ systematically reduces $r$ in the $(n_s, r)$ plane, while the shift in $n_s$ depends on the power $n$: for $n \geq 4$, the spectral index increases with $|\xi|$, whereas for $n < 4$, it decreases. Notably, the quartic model $V(\phi) = \lambda \phi^4/4$ with $\xi \lesssim -0.1$ shows good agreement with the ACT DR6 data and exhibits a distinct $n_s(\xi)$ dependence compared to other monomial cases. Our results demonstrate that non-minimally coupled models can effectively reconcile Planck and ACT observations, providing a unified framework for interpreting current CMB constraints.
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High Energy Physics (Theory)
Recursion Relations for Classical Gravity
Poul H. Damgaard, Kwangeon Kim and Kanghoon Lee
We derive a set of recursion relations for the perturbative evaluation of the scattering of two black holes in Einstein
gravity. To illustrate, we solve the equations up to third post-Minkowskian order in the gravitational coupling constant G, recovering the correct result, including the back-reaction from gravitational radiation.
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Earth and Planetary Astrophysics
When Stabilizing Feedbacks Wreak Havoc in Habitable Planets: Chaos at the Freezing Point in a Four-Feedback Climate Model
Chaucer Langbert, Dániel Apai and Renu Malhotra
The long-term habitability of Earth-like
planets is governed by the balance of positive and negative
climate feedbacks that regulate surface temperature and atmospheric composition. While some feedbacks, such as ice-albedo and silicate weathering, are thought to operate on many terrestrial
planets, the number and strength of additional
climate feedbacks may vary substantially from world to world. An important open question is whether and how the introduction of an additional
climate feedback influences long-term
climate evolution and complexity. To investigate this question, we extended a low-order
climate model including outgoing longwave radiation, ice–albedo, and carbonate–silicate weathering, with an additional generalized feedback. Across 35,864 simulations, we characterized dynamical behavior using the largest Lyapunov exponent (LLE). While 10.4% of explored parameter combinations exhibited positive LLEs, indicating chaos, the fraction rose to 25.6% within the stabilizing, near-freezing regime. This suggests that chaotic behavior is preferentially concentrated where a strong stabilizing feedback operates in the same temperature regime as a strong destabilizing feedback, contrary to the expectation that additional negative feedbacks should increase
climate stability. Increasing normalized volcanic outgassing shifts the chaotic regime toward lower
stellar flux and partially suppresses chaos at high instellation.
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High Energy Astrophysical Phenomena
A new model for the continuum spectra of AM CVn binaries and multi-messenger inference with normalizing flows
Nathan Steinle, Samar Safi-Harb, Austin MacMaster et al. (+5 more)
Future electromagnetic
telescopes, such as $\textit{NewAthena}$, $\textit{CASTOR}$, and an $\textit{AXIS}$-like mission, along with milli-Hz gravitational-wave (GW) detectors such as $\textit{LISA}$, are expected to unearth the population of
Galactic ultra-compact binaries (UCBs). Joint multi-messenger detections will probe the uncertain formation,
evolution, and observables of mass-transferring UCBs such as AM CVns, but theoretical tools need to be advanced to anticipate future data challenges. Motivated by this, we present a new forward model for the continuum emission of AM CVn binaries that connects source binary parameters to X-ray, optical, and ultraviolet observables. The model assumes GW-driven mass transfer with physically motivated prescriptions for
accretion energetics, emission geometry, absorption, and instrumental response. Combining this with $\textit{LISA}$ observations and the output of binary population synthesis enables exploration of the multi-messenger properties of AM CVns. Although uncertain, our model predicts that approximately one per $7000$ AM CVn binaries will permit a joint multi-messenger detection with $\textit{LISA}$, $\textit{CASTOR}$, and $\textit{AXIS}$. We also develop a framework for inferring binary parameters from the inverse model with a convolutional neural net and normalizing flows. Testing the trained flow with our synthetic AM CVn population, we find mean absolute fractional error on the inferred accretor mass of $0.05$, donor mass of $0.26$, orbital period of $0.1$, and distance of $0.2$, while Spearman's rank shows strongly correlated true and predicted distributions except for the donor mass. These efforts lay a foundation for follow-up studies that will explore detailed binary astrophysics and observational requirements for effective multi-messenger scientific discovery in the coming decade.
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All authors Nathan Steinle, Samar Safi-Harb, Austin MacMaster, Liliana Rivera Sandoval, Katelyn Breivik, Tyrone E. Woods, Tom Maccarone, Tom Wagg
Quantum Physics
Maximal Classicalization of Finite-Group Quantum Reference-Frame Noise
Maxim V. Churilov
A finite
quantum reference
token with group-valued misalignment induces a random-
unitary channel, but optimal degradation is generally an optimization over all
quantum post-processings. For a
unitary representation U of a finite group G, we prove that the following conditions are equivalent: U contains every irreducible type; one ancilla-assisted input has an orthonormal G-orbit; signed group measures embed isometrically into channels in diamond norm; and, for every pair of noise laws p,q, $\inf_{\Lambda\in\mathrm{CPTP}} \frac{1}{2}\|\Phi_q^U-\Lambda\circ\Phi_p^U\|_\diamond =\min_{r\in\mathcal{P}(G)}\frac{1}{2}\|q-r*p\|_1$. Thus representation completeness is the exact carrier condition for universal reduction of
quantum post-processing to classical convolution. We determine the minimum ancilla dimensions for an orthogonal orbit and for an invariant calibration seed. For an incomplete carrier, with visible Plancherel dimension S(U), we derive the exact conditional-expectation distance $\frac{1}{2}\|\operatorname{id}-\Phi_u^U\|_\diamond=1-1/S(U)$ and an explicit
quantum–classical deficiency gap. For irreducible carriers the deficiency is obtained in closed form; the faithful two-dimensional representation of $S_3$ yields an exact ten-percent reduction relative to classical convolution. We also characterize law identifiability through the conjugation representation, provide finite linear programs and decision witnesses, and establish both a finite-dimensional obstruction and stable visible-band reconstruction for infinite compact groups. Deterministic ancillary code reproduces the finite-group examples and numerical regression checks.
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High Energy Astrophysical Phenomena
High-Resolution Numerical Calculations of GRB Afterglow Plateaus arising from Stratified Ejecta
Paul C. Duffell and Ranadeep Ghosh Dastidar
Since the discovery of plateaus in GRB afterglows by Swift, they have been modeled predominantly by late-time energy injection. However, many studies have suggested that the plateau may be modeled by an early phase before reverse shock crossing (either coasting with constant Lorentz factor or decelerating very slowly as the reverse shock crosses the ejecta). The slope of the early plateau provides some constraints the stratification of the fastest-moving ejecta, which could be the ejecta responsible for the
prompt emission. However, numerical studies typically do not model the jet as a stratified
outflow; the reason being the extremely high resolution required in order to accurately evolve this tiny amount of highly relativistic material. In this study, we perform high-resolution numerical calculations ($\Delta r/r \lesssim 10^{-5}$) verifying that a stratified ejecta structure can indeed produce an afterglow plateau in both wind ($k=2$) and ISM ($k=0$) environments, and computing break times explicitly. We evolve the relativistic hydrodynamics using the JET code, and post-process this to compute the afterglow using the Firefly code. Our results show that a stratified ejecta structure (which should generically be present in GRB jets) is sufficient to explain GRB afterglows, and the plateau slopes can be used to constrain the ejecta stratification. We additionally provide precise measured scalings for the plateau duration as a function of the characteristic Lorentz factor of the ejecta. The long duration of typical plateaus requires a very modest characteristic Lorentz factor for the ejecta ($\gamma_0 \sim 10-50$), in agreement with other afterglow plateau models.
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Quantum Physics
Nonreciprocal Quantum Mpemba Effect
Wei-Bin Yan, Ying-Jie Zhang, Yun-Jie Xia et al. (+2 more)
We demonstrate a nonreciprocal
quantum Mpemba effect. Consider a broad class of open
quantum systems, each coupled to two isomorphic reservoirs through symmetric ports. Interchanging the parameters of the two reservoirs – a discrete operation we call the swap – turns the
quantum Mpemba effect on or off without changing the initial states. The swap modifies the Liouvillian, yet a structural
symmetry pins the
eigenvalues while rotating only the eigenvectors. The nonreciprocity therefore leaves no trace in the spectrum and is carried entirely by the eigenvectors. Concretely, the swap alters the far state's projection onto the slowest mode, switching whether it bypasses the slowest relaxation channel. At a Liouvillian exceptional point, the far state's relaxation switches from bypassing the slowest mode to avoiding the critical slowing, with the on–off contrast intact. There the spectrum-independent mechanism takes its purest form.
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All authors Wei-Bin Yan, Ying-Jie Zhang, Yun-Jie Xia, Heng Fan, Zhong-Xiao Man
Astrophysics of Galaxies
Dynamical modelling of giant radio quasars in the HETDEX Spring Field
T. M. O. Franzen, J. Machalski, M. Jamrozy et al. (+4 more)
Giant radio sources are defined as extragalactic
radio sources, hosted by
galaxies or
quasars, with linear sizes $\geq 0.7$ Mpc. They are thought to represent the final stage of the
evolution of
radio galaxies whose sizes range from pc to Mpc scales. We analyse in detail the
radio morphology and spectra between 54 MHz and 4.85/15.5 GHz of 15
giant radio quasars (GRQs) in the HETDEX Spring Field, and fit dynamical
evolution models to the sources' observational properties to study their physical parameters (age of the lobes, jet power, ambient medium density etc.). We compare the physical parameters of the GRQs with published results for a compiled sample of Fanaroff-Riley type II
radio sources. We find that the GRQs evolve in significantly lower medium densities, both at the central core radius and in front of the lobes, than smaller-sized
radio quasars (RQs) with similar jet powers. The derived central core densities for both populations are, however, highly sensitive to the assumed ambient medium density profile. For both populations combined, the jet power, $Q_{\text{j}}$, is anti-correlated with the age of the lobes, $t_l$ ($R = -0.67$, where $R$ is the Pearson correlation coefficient), as well as the linear size, $D_l$ ($R=-0.32$), but $t_l$ is a much stronger indicator of $Q_{\text{j}}$ than $D_l$. Using a Spearman partial rank correlation analysis, we demonstrate that there is a fundamental relation between $Q_{\text{j}}$, $t_l$, and $D_l$, despite the strong underlying correlation between age and size.
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All authors T. M. O. Franzen, J. Machalski, M. Jamrozy, R. Morganti, D. A. Green, Y. C. Perrott, T. W. Shimwell
Soft Condensed Matter
Active Quantum Nematics: The First Quantization
Ghansham Chandel and Siddhartha Das
Nematic
symmetry entails conserved quantized quantities such as number of topological defects and vorticity
cells. Correspondingly, countless
quantum analogies have been found in Active Nematics. We formalize Active Nematics and
Liquid Crystal theory into the framework of
Quantum Mechanics by introducing a complex valued Nematic Wavefunction to the Beris Edward equations, thus splitting spatiotemporally varying nematic systems into quantized states. We obtain the Planck's energy-frequency relationship for active micro-swimmers such as peristaltic worms and bacterium as a consequence of local complex phase-
symmetry of the governing equations, similar to the gauge formulation of Electromagnetism. For organisms operating on diffusive chemotaxis, we obtain predator-prey dynamics that evolve to maximize/minimize pheromones field gradient overlap. Furthermore, when quantizing beating hearts, similar to the orbitals of hydrogen atoms, the state-function allows us to characterize hearts not only through the rhythm, but also the spaciotemporal distribution of contractile activity of various harmonics among healthy and unhealthy hearts.
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Materials Science
Decoupling Strain-Rate Sensitivity and Deformation Length Scale Effects in Neutron-Irradiated Tungsten: A Coupled Nano-Indentation, HR-EBSD and Crystal Plasticity Study
Prashil S. Joshi, Bethany Jim, Chris Hardie et al. (+3 more)
Strain-rate-dependent deformation in spherical nanoindentation couples material rate sensitivity effects with the evolving contact radius, penetration depth and plastic-zone size. A rate-sensitive model where loading rate and indentation depth are prescribed independently allows their contributions to be disentangled. We study this in unirradiated and
neutron-irradiated single-
crystal tungsten, indented to the same final indentation strain at nominal strain-rates of 3.2e-5 to 3.2e-3 per second and reaching different final depths. Surface pile-up, residual
lattice strain and dislocation distributions were measured by AFM and HR-EBSD. A rate-sensitive, strain-gradient
crystal plasticity framework, incorporating thermally activated slip and irradiation hardening derived from measured defect populations, was calibrated at the highest strain rate and reproduced all these observables at the two lower strain rates without further parameter adjustment. The framework was then used to vary strain rate and depth independently. At fixed depth, strain rate over the experimental range changes the predicted peak load by < 1% and the pile-up by < 2 nm. At fixed strain rate, the experimental depth differences alone produce pile-up increases of ~ 90% and 130%, comparable to the measured 66% and 150% for unirradiated and irradiated tungsten. The measured differences between strain rate conditions therefore predominantly reflect the different depths reached; a 10% difference in final depth mimics more than an order of magnitude change in strain rate. Irradiation is seen to promote localisation, with its effect on pile-up increasing with depth up to ~ 500 nm, while remaining consistent with a common thermally activated deformation mechanism.
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All authors Prashil S. Joshi, Bethany Jim, Chris Hardie, Angus Wilkinson, David EJ Armstrong, Suchandrima Das