arXiv subjects

Alexey Ilin

Publications and source records attributed to Alexey Ilin.

6 recordsLinked to original sources

arXiv2026

Selective braiding of different anyons in the even-denominator fractional quantum Hall effect

Even-denominator quantum Hall states can host several types of anyons with distinct exchange statistics. Depending on the anyon type, exchanging two quasiparticles can impart a phase to the many-body wave function or even transform it into a different state. Here, we realize a gate-tunable Fabry-P\'erot interferometer with an embedded antidot that provides local control over the number of anyons within the interference loop. By independently tuning the magnetic field, carrier densities across the device, and the antidot potential, we access regimes in which localized anyons form reproducibly and measure the associated statistical phases $e^{i \theta_\mathrm{braid}}$. We resolve braiding phases of $\theta_{\mathrm{braid}}=\pi$ and $\theta_{\mathrm{braid}}=\frac{\pi}{2}$, which we attribute to $e/2$ quasiparticles encircling either $e/2$ or $e/4$ quasiparticles, respectively. We further observe switching between different anyon occupancies of the antidot over time, directly resolving individual anyon tunnelling events into the interference loop. Similar behavior occurs at filling factor one third. Our work addresses one of the two key challenges in observing non-Abelian braiding, which requires control of both localized and interfering anyon types.

cond-mat.mes-hall↗

arXiv2025

Text-to-SQL for Enterprise Data Analytics

The introduction of large language models has brought rapid progress on Text-to-SQL benchmarks, but it is not yet easy to build a working enterprise solution. In this paper, we present insights from building an internal chatbot that enables LinkedIn's product managers, engineers, and operations teams to self-serve data insights from a large, dynamic data lake. Our approach features three components. First, we construct a knowledge graph that captures up-to-date semantics by indexing database metadata, historical query logs, wikis, and code. We apply clustering to identify relevant tables for each team or product area. Second, we build a Text-to-SQL agent that retrieves and ranks context from the knowledge graph, writes a query, and automatically corrects hallucinations and syntax errors. Third, we build an interactive chatbot that supports various user intents, from data discovery to query writing to debugging, and displays responses in rich UI elements to encourage follow-up chats. Our chatbot has over 300 weekly users. Expert review shows that 53% of its responses are correct or close to correct on an internal benchmark set. Through ablation studies, we identify the most important knowledge graph and modeling components, offering a practical path for developing enterprise Text-to-SQL solutions.

cs.CL↗

arXiv2024

Aharonov-Bohm Interference in Even-Denominator Fractional Quantum Hall States

Position exchange of non-Abelian anyons affects the quantum state of their system in a topologically-protected way. Their expected manifestations in even-denominator fractional quantum Hall (FQH) systems offer the opportunity to directly study their unique statistical properties in interference experiments. In this work, we present the observation of coherent Aharonov-Bohm interference at two even-denominator states in high-mobility bilayer graphene-based van der Waals heterostructures by employing the Fabry-P\'erot interferometry (FPI) technique. Operating the interferometer at a constant filling factor, we observe an oscillation period corresponding to two flux quanta inside the interference loop, $\Delta\Phi=2\Phi_0$, at which the interference does not carry signatures of non-Abelian statistics. The absence of the expected periodicity of $\Delta\Phi=4\Phi_0$ may indicate that the interfering quasiparticles carry the charge $e^* = \frac{1}{2}e$ or that interference of $e^* = \frac{1}{4}e$ quasiparticles is thermally smeared. Interestingly, at two hole-conjugate states, we also observe oscillation periods of half the expected value, indicating interference of $e^* = \frac{2}{3}e$ quasiparticles instead of $e^* = \frac{1}{3}e$. To probe statistical phase contributions, we operated the FPI with controlled deviations of the filling factor, thereby introducing fractional quasiparticles inside the interference loop. The resulting changes to the interference patterns at both half-filled states indicate that the additional bulk quasiparticles carry the fundamental charge $e^*=\frac{1}{4}e$, as expected for non-Abelian anyons.

cond-mat.mes-hall↗

arXiv2024

Competing Orbital Magnetism and Superconductivity in electrostatically defined Josephson Junctions of Alternating Twisted Trilayer Graphene

The coexistence of superconductivity and magnetism within a single material system represents a long-standing goal in condensed matter physics. Van der Waals-based moir\'e superlattices provide an exceptional platform for exploring competing and coexisting broken symmetry states. Alternating twisted trilayer graphene (TTG) exhibits robust superconductivity at the magic angle of 1.57{\deg} and 1.3{\deg}, with suppression at intermediate twist angles. In this study, we investigate the intermediate regime and uncover evidence of orbital magnetism. As previously reported, superconductivity is suppressed near the charge neutrality point (CNP) and emerges at larger moir\'e fillings. Conversely, we find orbital magnetism most substantial near the CNP, diminishing as superconductivity develops. This complementary behavior is similarly observed in the displacement field phase space, highlighting a competitive interplay between the two phases. Utilizing gate-defined Josephson junctions, we probe orbital magnetism by electrostatically tuning the weak links into the magnetic phase, revealing an asymmetric Fraunhofer interference pattern. The estimated orbital ferromagnetic ordering temperature is approximately half the superconducting critical temperature, coinciding with the onset of Fraunhofer asymmetry. Our findings suggest that the observed orbital magnetism is driven by valley polarization and is distinct from the anomalous Hall effect reported at integer fillings in twisted graphene systems. These results offer insights into the interplay between superconductivity and magnetism in moir\'e superlattices.

cond-mat.str-el↗

arXiv2024

Quarter- and half-filled quantum Hall states and their topological orders revealed by daughter states in bilayer graphene

Even-denominator fractional quantum Hall states are promising candidates for fault-tolerant quantum computing due to their underlying non-Abelian topological orders. However, the topological order of these states remains hotly debated. Here, we report transport measurements on ultra-clean bilayer graphene heterostructures, where we observed four quarter-filled states and their corresponding Levin-Halperin daughter states, constraining their topological order. Moreover, we complete the sequence of half-filled plateaus by detecting states at v=-3/2 and v=1/2 whose daughters suggest an alternating sequence of non-Abelian orders. This pattern suggests a universal origin supporting their use in identifying topological order at even-denominator fillings, though further confirmation is needed via direct measurements. The observed quarter- and half-filled states appear in N=0 and N=1 Landau levels, respectively, and thus highlight a competition between interactions favoring paired states of either four- or two-flux composite fermions. Additionally, we observe several 'next-generation' quantum Hall states that require strong interactions between composite fermions.

cond-mat.mes-hall↗

arXiv2024

Aharonov-Bohm interference and the evolution of phase jumps in fractional quantum Hall Fabry-Perot interferometers based on bi-layer graphene

Quasi-particles in fractional quantum Hall states are collective excitations that carry fractional charge and anyonic statistics. While the fractional charge affects semi-classical characteristics such as shot noise and charging energies, the anyonic statistics is most notable in quantum interference phenomena. In this study, we utilize a versatile bilayer graphene-based Fabry-P\'erot Interferometer (FPI) that facilitates the study of a broad spectrum of operating regimes, from Coulomb-dominated to Aharonov-Bohm, for both integer and fractional quantum Hall states. Focusing on the $\nu$=$1 \over 3$ fractional quantum Hall state, we study the Aharonov-Bohm interference of quasi-particles when the magnetic flux through an interference loop and the charge density within the loop are independently varied. When their combined variation is such that the Landau filling remains $1 \over 3$ we observe pristine Aharonov-Bohm oscillations with a period of three flux quanta, as is expected from the interference of quasi-particles of one-third of the electron charge. When the combined variation is such that it leads to quasi-particles addition or removal from the loop, phase jumps emerge, and alter the phase evolution. Notably, across all cases, the average phase consistently increases by 2$\pi$ with each addition of one electron to the loop.

cond-mat.mes-hall↗