Publications

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Coupled dynamics of resource competition and constrained entrances in a multi-lane bidirectional exclusion process

Ashish Kumar Pandey, Arvind Kumar Gupta

SciPost Phys. Core 8, 089 (2025) · published 3 December 2025 | · pdf

Motivated by the role of limited particle resources in multi-species bidirectional transport processes observed in various biological and physical systems, we investigate a one-dimensional closed system consisting of two parallel lanes with narrow entrances, where each lane accommodates two oppositely directed particle species. Each particle species is linked to a separate finite reservoir, which is coupled to both lanes and regulates the entry rates of particle into the lanes. To analyze the effect of finite particle reservoirs on the stationary properties of the system, we employ a mean-field theoretical framework to characterize the density profiles, particle currents, and phase behavior, complemented by a boundary layer analysis based on fixed point methods to capture spatial variations near the boundaries. The impact of individual species population, quantified by species-specific filling factors, is systematically examined under both equal and unequal conditions. For equal filling factors, system undergoes spontaneous symmetry breaking and supports both symmetric and asymmetric phases. In contrast, for unequal filling factors, only asymmetric phases are realized, with the phase diagram exhibiting up to five distinct phases. A striking feature observed in both scenarios is the emergence of a back-and-forth transition, along with a non-monotonic dependence of the number of phases on the filling factors. All theoretical findings are extensively validated through stochastic simulations based on the Gillespie algorithm, confirming the robustness of the analytical results.
Classification of topological insulators and superconductors with multiple order-two point group symmetries

Ken Shiozaki

SciPost Phys. Core 8, 088 (2025) · published 28 November 2025 | · pdf

We present a method for computing the classification groups of topological insulators and superconductors in the presence of $\mathbb{Z}_2^{× n}$ point group symmetries, for arbitrary natural numbers $n$. Each symmetry class is characterized by four possible additional symmetry types for each generator of $\mathbb{Z}_2^{× n}$, together with bit values encoding whether pairs of generators commute or anticommute. We show that the classification is fully determined by the number of momentum- and real-space variables flipped by each generator, as well as the number of variables simultaneously flipped by any pair of generators. As a concrete illustration, we provide the complete classification table for the case of $\mathbb{Z}_2^{× 2}$ point group symmetry.
Inferring correlated distributions: Boosted top jets

Ezequiel Alvarez, Manuel Szewc, Alejandro Szynkman, Santiago Tanco, Tatiana Tarutina

SciPost Phys. Core 8, 087 (2025) · published 26 November 2025 | · pdf

Improving the understanding of signal and background distributions in signal-region is a valuable key to enhance any analysis in collider physics. This is usually a difficult task because –among others– signal and backgrounds are hard to discriminate in signal-region, simulations may reach a limit of reliability if they need to model non-perturbative QCD, and distributions are multi-dimensional and many times may be correlated within each class. Bayesian density estimation is a technique that leverages prior knowledge and data correlations to effectively extract information from data in signal-region. In this work we extend previous works on data-driven mixture models for meaningful unsupervised signal extraction in collider physics to incorporate correlations between features. Using a standard dataset of top and QCD jets, we show how simulators, despite having an expected bias, can be used to inject sufficient inductive nuance into an inference model in terms of priors to then be corrected by data and estimate the true correlated distributions between features within each class. We compare the model with and without correlations to show how the signal extraction is sensitive to their inclusion and we quantify the improvement due to the inclusion of correlations using both supervised and unsupervised metrics.
Digital quantum simulation of bosonic systems and quantum complementarity

Victor P. Brasil, Diego S. Starke, Jonas Maziero

SciPost Phys. Core 8, 086 (2025) · published 24 November 2025 | · pdf

Digital quantum simulation (DQS) has emerged as a powerful approach to investigate complex quantum systems using digital quantum computers. Such systems, like many-particle bosonic systems and intricate optical experimental setups, pose significant challenges for classical simulation methods. In this paper, we utilize a general formalism for the DQS of bosonic systems, which consists of mapping bosonic operators to Pauli operators using the Gray code, in order to simulate interferometric variants of Afshar's experiment—an intricate optical experiment—on IBM's quantum computers. We investigated experiments analogous to Afshar's double-slit experiment performed by Unruh and Pessoa Júnior, exploring discussions on the apparent violation of Bohr's complementarity principle when considering the entire experimental setup. Based on the aforementioned experiments, we construct a variation of a delayed-choice setup. We also explore another experiment starting with a two-photon initial state. Finally, we analyze these experiments within the framework of an updated quantum complementarity principle, which applies to specific quantum state preparations and remains consistent with the foundational principles of Quantum Mechanics.
A Fermi surface descriptor quantifying the correlations between anomalous Hall effect and Fermi surface geometry

Elena Derunova, Jacob Gayles, Yan Sun, Michael W. Gaultois, Mazhar N. Ali

SciPost Phys. Core 8, 085 (2025) · published 18 November 2025 | · pdf

In the last few decades, basic ideas of topology have completely transformed the prediction of quantum transport phenomena. Following this trend, we go deeper into the incorporation of modern mathematics into quantum material science focusing on geometry. Here we investigate the relation between the geometrical type of the Fermi surface and Anomalous and Spin Hall Effects. An index, $\mathbb{H}_F$, quantifying the hyperbolic geometry of the Fermi surface, shows a universal correlation (R$^2$ = 0.97) with the experimentally measured intrinsic anomalous Hall conductivity, of 16 different compounds spanning a wide variety of crystal, chemical, and electronic structure families, including those where topological methods give R$^2$ = 0.52. This raises a question about the predictive limits of topological physics and its transformation into a wider study of bandstructures' and Fermi surfaces' geometries and relating them to the quantum geometry theory of a more general metric of eigenstates, opening horizon for the prediction of phenomena beyond topological understanding.
Quantum adiabaticity in many-body systems and almost-orthogonality in complementary subspace

Jyong-Hao Chen, Vadim Cheianov

SciPost Phys. Core 8, 084 (2025) · published 12 November 2025 | · pdf

We investigate why, in quantum many-body systems, the adiabatic fidelity and the overlap between the initial state and instantaneous ground states often yield nearly identical values. Our analysis suggests that this phenomenon results from an interplay between two intrinsic limits of many-body systems: the limit of small evolution parameters and the limit of large system sizes. In the former case, conventional perturbation theory provides a straightforward explanation. In the latter case, a key insight is that pairs of vectors in the Hilbert space orthogonal to the initial state tend to become nearly orthogonal as the system size increases. We illustrate these general findings with two representative models of driven many-body systems: the driven Rice-Mele model and the driven interacting Kitaev chain model.
Exact solution for two $\delta$-interacting bosons on a ring in the presence of a $\delta$-barrier: Asymmetric Bethe Ansatz for spatially odd states

Maxim Olshanii, Mathias Albert, Gianni Aupetit-Diallo, Patrizia Vignolo, Steven G. Jackson

SciPost Phys. Core 8, 083 (2025) · published 12 November 2025 | · pdf

In this article, we apply the recently proposed Asymmetric Bethe Ansatz method to the problem of two one-dimensional, short-range-interacting bosons on a ring in the presence of a $\delta$-function barrier. Only half of the Hilbert space—namely, the two-body states that are odd under point inversion about the position of the barrier—is accessible to this method. The other half is presumably non-integrable. We consider benchmarking the recently proposed $1/g$ expansion about the hard-core boson point [D. Sen, Int. J. Mod. Phys. A 14, 1789 (1999); A. G. Volosniev et al., Nat. Commun. 5, 5300 (2014)] as one application of our results. Additionally, we find that when the $\delta$-barrier is converted to a $\delta$-well with strength equal to that of the particle-particle interaction, the system exhibits the spectrum of its non-interacting counterpart while its eigenstates display features of a strongly interacting system. We discuss this phenomenon in the "Summary and Future Research" section of our paper.
Spin-orbit photonics in a fixed cavity: Harnessing Bogoliubov modes of a Bose-Einstein condensate

Ghaisud Din, Muqaddar Abbas, Pei Zhang

SciPost Phys. Core 8, 082 (2025) · published 12 November 2025 | · pdf

We present a theoretical investigation of spin-orbit photonics within a fixed mirror cavity system containing a Bose-Einstein condensate (BEC), in which the Bogoliubov excitation modes of the condensate are treated as effective mechanical oscillators. By embedding the condensate in a single-mode optical cavity, we explore the emergence and modulation of the photonic spin Hall effect (PSHE) through the spin-dependent transverse shifts of a weak probe field. The optical response —encoded in the real and imaginary components of the output field susceptibility— is systematically analyzed as a function of the condensate-cavity coupling strength, revealing a controllable enhancement or suppression of the spin-orbit interaction. Our model captures how the interplay between collective BEC excitations and cavity photon dynamics induces nontrivial modifications in spin-dependent light propagation. Notably, we uncover that the Bogoliubov mode coupling acts as a tunable channel for mediating spin angular momentum transfer within the cavity, offering a novel route for engineering compact, quantum-coherent spin-orbit photonic devices.
A graph-theoretic approach to chaos and complexity in quantum systems

Maxwell West, Neil Dowling, Angus Southwell, Martin Sevior, Muhammad Usman, Kavan Modi, Thomas Quella

SciPost Phys. Core 8, 081 (2025) · published 10 November 2025 | · pdf

There has recently been considerable interest in studying quantum systems via dynamical Lie algebras (DLAs) – Lie algebras generated by the terms which appear in the Hamiltonian of the system. However, there are some important properties that are revealed only at a finer level of granularity than the DLA. In this work we explore, via the commutator graph, average notions of scrambling, chaos and complexity over ensembles of systems with DLAs that possess a basis consisting of Pauli strings. Unlike DLAs, commutator graphs are sensitive to short-time dynamics, and therefore constitute a finer probe to various characteristics of the corresponding ensemble. We link graph-theoretic properties of the commutator graph to the out-of-time-order correlator (OTOC), the frame potential, the frustration graph of the Hamiltonian of the system, and the Krylov complexity of operators evolving under the dynamics. For example, we reduce the calculation of average OTOCs to a counting problem on the graph; separately, we connect the Krylov complexity of an operator to the module structure of the adjoint action of the DLA on the space of operators in which it resides, and prove that its average over the ensemble is lower bounded by the average shortest path length between the initial operator and the other operators in the commutator graph.
Numerical study of disordered noninteracting chains coupled to a local Lindblad bath

Viktor Berger, Andrea Nava, Jens Hjorleifur Bardarson, Claudia Artiaco

SciPost Phys. Core 8, 080 (2025) · published 10 November 2025 | · pdf

Disorder can prevent many-body quantum systems from reaching thermal equilibrium, leading to a many-body localized phase. Recent works suggest that nonperturbative effects caused by rare regions of low disorder may destabilize the localized phase. However, numerical simulations of interacting systems are generically possible only for small system sizes, where finite-size effects might dominate. Here we perform a numerical investigation of noninteracting disordered spin chains coupled to a local Lindblad bath at the boundary. Our results reveal strong finite-size effects in the Lindbladian gap in both bath-coupled Anderson and Aubry-André-Harper models, leading to a non-monotonic behavior with the system size. We discuss the relaxation properties of a simple toy model coupled to local Lindblad baths, connecting its features to those of noninteracting localized chains. We comment on the implications of our findings for many-body systems.

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