arXiv subjects

Alexander V. Balatsky

Publications and source records attributed to Alexander V. Balatsky.

At least 19 recordsLinked to original sources

arXiv2026

Automating detection of Two-Level Systems in Superconducting Qubits

Microscopic two-level system (TLS) defects remain a primary mechanism of decoherence and operational instability in superconducting transmon qubits, necessitating scalable and automated methods for their characterization. Here, we present and benchmark two complementary analysis pipelines for extracting TLS statistics directly from time-resolved SWAP spectroscopy: one-dimensional decay-rate fitting (1D-DRF), which detects defects via localized enhancements in the qubit relaxation rate, and a deterministic, non-parametric computer-vision framework (2D-CV) that achieves two-dimensional spectral localization by exploiting the temporal persistence of coherent population suppression. We deploy both methods on SWAP spectroscopy measurements from 52 flux-tunable transmon qubits on Rigetti processors with and without moderate ($\sim 10\%$) post-fabrication frequency trimming via Alternating-Bias Assisted Annealing (ABAA). We show that both pipelines converge on a consistent global characterization of the defect landscape while exhibiting complementary sensitivity across distinct coupling regimes. Crucially, both methods independently reveal a count--loss decoupling under moderate annealing: while the total detectable TLS defect density remains statistically unchanged, the span-integrated dielectric loss is reduced by approximately a factor of two, demonstrating selective suppression of the most strongly dissipative defect channels. These results establish an automated, non-parametric analysis framework for high-throughput hardware diagnostics and provide a statistical baseline for post-fabrication defect engineering in large-scale superconducting quantum processors.

quant-ph↗

arXiv2026

Light induced superconducting diode effect in patterned films

Structured light offers a route to control superconducting transport without permanently modifying the material or applying a static bias. Here we show that structured optical driving can generate a superconducting diode response in patterned superconducting films with asymmetric holes. Using generalized time-dependent Ginzburg Landau simulations, we find that optical driving produces rectified dc photovoltages and zero bias directional supercurrent imbalance in a junction free geometry, with continuous-drive diode efficiencies of order $10^{-3}$ and pulsed efficiencies reaching $10^{-2}$. The response is controlled by both the hole array and the optical mode. Increasing the number of asymmetric holes enhances rectification, reversing circular helicity reverses the diode polarity, and the optical spatial mode strongly modifies the magnitude and polarity of the directional response. Pulsed excitation enhances the zero bias line cut current imbalance to the percent level. For linearly polarized illumination, the asymmetric metacrystal converts the drive into local chiral supercurrent motion, inducing an inverse Faraday effect like mechanism for dynamical time reversal symmetry breaking. These results establish patterned superconducting films as a viable platform for light-tunable superconducting diode behavior.

cond-mat.supr-con↗

arXiv2026

Quantum turbulence in the many-body regime

We discuss phenomenology associated with turbulent hydrodynamics in quantum fluids from a condensed-matter perspective. We begin with weakly-interacting superfluids, often modeled by a mean-field theory governed by the Gross-Pitaevskii equation. Considering the effect of quantum fluctuations beyond the mean-field approximation, we propose a study of many-body quantum effects in turbulent hydrodynamics, especially near zero temperature. We motivate examples of quantum many-body systems where such effects may be uncovered. These include bosons confined in a periodic potential in low spatial dimensions (one and two), and the associated quantum critical point of the superfluid-insulator transition, realized in present-day ultracold-atom and quantum computing platforms. We conclude by listing a set of (open) questions that may be answered using modern quantum many-body techniques. This article is part of the theme issue 'Frontiers of turbulence and statistical physics'.

cond-mat.quant-gas↗

arXiv2026

Eight-fold classification of superconducting orders

We present a symmetry-based classification for superconducting pairing states, organized by the exchange properties of the anomalous correlation function rather than by a specific microscopic pairing mechanism. The classification is built from the pairwise permutation of spin, orbital, spatial, and temporal indices, leading to the fermionic constraint ${\cal S} {\cal P}^\ast {\cal O} {\cal T}^\ast = -1$, and is further organized by separating relative and center-of-mass space-time coordinates. This construction defines what we call the Berezinskii--Abrahams hypercube, in which conventional Bardeen--Cooper--Schrieffer superconductivity, unconventional $p$- and $d$-wave pairing, odd-frequency superconductivity, Fulde--Ferrell--Larkin--Ovchinnikov states, pair-density-wave states, and time-modulated superconducting orders appear as different sectors of a unified framework. Beyond organizing known phases, the Berezinskii--Abrahams hypercube identifies symmetry-allowed hybrid orders that have received comparatively little attention, including odd-frequency Fulde--Ferrell--Larkin--Ovchinnikov or pair-density-wave states and odd-frequency time-modulated superconducting states. We discuss microscopic routes, candidate platforms, experimental signatures, and stability constraints for these sectors, emphasizing the distinction between symmetry allowance and physical realizability. We also present the proximity induced odd-frequency pair-density-wave state, and its driven analog as the two new examples of the states that naturally emerge in the Berezinskii--Abrahams hypercube. The resulting framework provides a guide for connecting established superconducting phenomena with unexplored symmetry-allowed forms of order.

cond-mat.supr-con↗

arXiv2026

Quantum Printing: Laguerre-Gaussian Beam Induced Topological Magnetic Textures

Structured light has become a practical tool for controlling matter by applying tailored, space- and time-dependent electromagnetic fields. We show that Laguerre-Gaussian pulses imprint non-collinear magnetic textures via the spatial structure of optical magnetic field. Our route offers a direct spatial selectivity determined by the optical features without relying on material anisotropic interactions. The proposed printing approach does not require interfacial anisotropy or bulk chirality, current-driven torques, or thermal quenching. We use micromagnetic simulations to demonstrate the potential to create topological charge density emerging during the pulse and reveal control through the optical topological properties and polarization. These results suggest structured-light quantum printing as a viable approach for magnonics and motivate studies toward reconfigurable topological textures enabled by ultrafast THz optics and non-thermal control.

cond-mat.mes-hall↗

arXiv2026

Generation of magnetic metal-organic frameworks

The potential to utilize metal-organic frameworks as a replacement for rare earth materials as well as in technological applications has prompted increased interested in this material class. The simulation of organic materials, including metal-organic frameworks (MOFs), represents a computational challenge due to an increased average number of atoms in the unit cell. Compounding this challenge, modern materials databases are generally limited to inorganic structures due to their utility in modern technologies such as batteries and integrated circuits. Machine-learning tools appear ideally suited to study these systems. However, organic materials are generally underrepresented in the training sets of foundational models. In this work we leverage the the Organic Materials Database (OMDB) to create a training dataset comprised of more than 15,000 single-point first-principles computations for finetuning machine learned interatomic potentials. Specifically, we fine tune CHGNet and implement a site substitution workflow to identify novel, highly magnetic, MOFs from structural prototypes within the QMOF database.

cond-mat.mtrl-sci↗

arXiv2026

Properties of topological insulators and superconductors under relativistic gravity

The interplay between the curved spacetimes of general relativity and quantum mechanical systems is an active field of research. However, analysis of relativistic gravitation on extended quantum systems remains understudied. To this end, we study here the effects of a general relativistic curved spacetime on the topological phases of the Su-Schrieffer-Heeger model and Kitaev superconducting wire. We find that the topological states remain robust and well localized. In the topological insulator we find that the energy level of the topological state becomes shifted away from zero according to the gravitational redshift, breaking the system's chiral symmetry. In contrast, the Majorana zero mode of the topological superconductor remains at zero energy. Furthermore, within the topological superconductor, we identify the possibility of a gravitationally induced topological phase transition leading to the formation of a domain wall, shifting one of the boundary Majorana zero modes into the bulk.

cond-mat.mes-hall↗

arXiv2025

Simulating alternating bias assisted annealing of amorphous oxide tunnel junctions

Amorphous oxide tunneling barriers, primarily formed from aluminum, represent one of the most widely adopted platforms for superconducting quantum bits (qubits). To overcome challenges associated with defects and sample variance among the tunneling barriers, the methodology of alternating bias assisted annealing (ABAA) was introduced in Pappas et. al[1]. The process of applying alternating bias to the barrier and subsequently aging before use was shown to reduce defects in the barrier. Namely, defects that give rise to two-level systems, coupling to the qubit and expediting decoherence. In this work we replicate an expedited ABAA process through a combination of ab-initio molecular dynamics and machine-learned potentials, illuminating how ABAA effects the energy landscape of the barrier.

cond-mat.mes-hall↗

arXiv2025

Kapitza-Dirac interference of Higgs waves in superconductors

We present a novel framework for controlling Higgs mode and vortex dynamics in superconductors using structured light. We propose a phenomenon analog of the Kapitza-Dirac effect in superconductors, where Higgs waves scatter off light-induced vortex lattices, generating interference patterns akin to matter wave diffraction. We also find that the vortices enable the linear coupling of Higgs mode to the electromagnetic field. This interplay between light-engineered Higgs excitations and emergent vortex textures opens a pathway to probe nonequilibrium superconductivity with unprecedented spatial and temporal resolution. Our results bridge quantum optics and condensed matter physics, offering new examples of quantum printing where one uses structured light to manipulate the collective modes in correlated quantum fluids.

cond-mat.str-el↗

arXiv2025

Tailoring Superconductivity with Two-Level Systems

We investigate the impact of two-level systems (TLSs) on superconductivity, treating them as soft modes localised in real space. We show that these defects can either enhance or suppress the superconducting critical temperature, depending on their surface density and average frequency. Using thin-film aluminium as a case study, we quantitatively describe how TLSs modify both the critical temperature and the zero-temperature superconducting gap. Our results thus highlight new opportunities for tailoring material properties through TLS engineering.

cond-mat.supr-con↗

arXiv2025

Accelerated characterization of two-level systems in superconducting qubits via machine learning

We introduce a data-driven approach for extracting two-level system (TLS) parameters-frequency $ω_{TLS}$, coupling strength $g$, dissipation time $T_{TLS, 1}$, and the pure dephasing time $T^ϕ_{TLS, 2}$, labelled as a 4-component vector $\vec{q}$, directly from simulated spectroscopy data generated for a single TLS by a form of two-tone spectroscopy. Specifically, we demonstrate that a custom convolutional neural network model(CNN) can simultaneously predict $ω_{TLS}$, $g$, $T_{TLS, 1}$ and $T^ϕ_{TLS, 2}$ from the spectroscopy data presented in the form of images. Our results show that the model achieves superior performance to perturbation theory methods in successfully extracting the TLS parameters. Although the model, initially trained on noise-free data, exhibits a decline in accuracy when evaluated on noisy images, retraining it on a noisy dataset leads to a substantial performance improvement, achieving results comparable to those obtained under noise-free conditions. Furthermore, the model exhibits higher predictive accuracy for parameters $ω_{TLS}$ and $g$ in comparison to $T_{TLS, 1}$ and $T^ϕ_{TLS, 2}$.

quant-ph↗

arXiv2025

Quantum Printing

We introduce the concept of quantum printing -- the imprinting of quantum states from photons and phonons onto quantum matter. The discussion is focusing on charged fluids (metals, superconductors, Hall fluids) and neutral systems (magnets, excitons). We demonstrate how structured light can generate topological excitations, including vortices in superconductors and skyrmions in magnets. We also discuss how quantum printing induces magnetization in quantum paraelectrics and strain-mediated magnetization in Dirac materials. Finally, we propose future applications, such as printing entangled photon states, creating entangled topological excitations, and discuss applications of quantum printing to light induced quantum turbulence in a charged fluid. This review represents the expanded version of the shorter review submitted to Nature Physics.

quant-ph↗

arXiv2025

Identification of soft modes in amorphous Al$_{2}$O$_{3}$ via first-principles

Amorphous Al$_{2}$O$_{3}$ is a fundamental component of modern superconducting qubits. While amphorphous oxides offer distinct advantages, such as directional isotropy and a consistent bulk electronic gap, in realistic systems these compounds support two-level systems (TLSs) which couple to the qubit, expediting decoherence. In this work, we perform a first-principles study of amorphous Al$_{2}$O$_{3}$ and identify low-energy modes in the electronic and phonon spectra as a possible origin for TLSs.

cond-mat.mes-hall↗

arXiv2025

Orbital Inverse Faraday and Cotton-Mouton Effects in Hall Fluids

We report two light-induced orbital magnetization effects in quantum Hall (QH) fluids, stemming from their transverse response. The first is a purely transverse contribution to the inverse Faraday effect (IFE), where circularly polarized light induces a DC magnetization by stirring the charged fluid. This contribution dominates the IFE in the QH regime. The second is the orbital inverse Cotton-Mouton effect (ICME), in which linearly polarized light generates a DC magnetization. Since the applied field in the ICME does not break time-reversal symmetry, the induced magnetization directly probes the chiral orbital response of the fluid at the driving frequency. We estimate that the resulting magnetization lies in the range of 0.5-10 Bohr magnetons per charge carrier in materials such as graphene and transition-metal dichalcogenides (TMDs) in the QH regime. Finally, we show that the induced magnetization is accompanied by a local correction to the static particle density, enabling optical quantum printing of density profiles into the QH fluid.

cond-mat.mes-hall↗

arXiv2025

Multipolar multiferroics in $4d^2$/$5d^2$ Mott insulators

We extend the concept of conventional multiferroicity \ -- where ferroelectric and ferromagnetic orders coexist \ -- to include multipolar degrees of freedom. Specifically, we explore how this phenomenon emerges in $4d^2/5d^2$ Mott insulators with strong spin-orbit and Hund's couplings. Our study uncovers the origin of magnetic multipolar interactions in these systems and demonstrates that a combination of quadrupolar and octupolar magnetic order can simultaneously induce both electrical quadrupolar moments and ferroelectric polarization. By expanding the multiferroic framework to higher-order multipoles, we reveal the possibility of coexisting multipolar orders of different or same ranks, paving the way for new functional properties in a large class of strongly correlated materials.

cond-mat.str-el↗

arXiv2025

Many-body effects of two-level systems in superconducting qubits

Superconducting qubits are often adversely affected by two-level systems (TLSs) within the Josephson junction, which contribute to decoherence and subsequently limit the performance of the qubit. By treating the TLS as a soft (i.e., low-frequency) bosonic mode localized in real space, we find that a single TLS in either the amorphous oxide surface or the superconducting bulk may result in a localized "hot spot" of amplified Josephson energy. Such amplification is shown to have a non-negligible effect on the $T_1$ time of certain superconducting qubits, regardless of whether or not the TLS is on resonance with the qubit frequency. With this study, we identify sources of decoherence unique to the superconducting element of superconducting quantum devices.

cond-mat.supr-con↗

arXiv2025

Quantum Sensing from Gravity as Universal Dephasing Channel for Qubits

We investigate the interaction of a transmon qubit with a classical gravitational field. Exploiting the generic phenomena of the gravitational redshift and Aharonov-Bohm phase, we show that entangled quantum states dephase with a universal rate. The gravitational phase shift is expressed in terms of a quantum computing noise channel. We give a measurement protocol based on a modified phase estimation algorithm which is linear in the phase drift, which is optimal for measuring the small phase that is acquired from the gravitation channel. Additionally, we propose qubit-based platforms as quantum sensors for precision gravitometers and mechanical strain gauges as an example of this phenomenon's utility. We estimate a sensitivity for measuring the local gravitational acceleration to be $δg/g \sim 10^{-7}$. This paper demonstrates that classical gravitation has a non-trivial influence on quantum computing hardware, and provides an illustration of how quantum computing hardware may be utilized for purposes other than computation. While we focus on superconducting qubits, we point the universal nature of gravitational phase effects for all quantum platforms.

quant-ph↗

arXiv2025

Large inverse Faraday effect for Rydberg states of free atoms and isolated donors in semiconductors

We report on the induction of magnetization in Rydberg systems by means of the inverse Faraday effect, and propose the appearance of the effect in two such systems, Rydberg atoms proper and shallow dopants in semiconductors. Rydberg atoms are characterized by a large orbital radius. This large radius gives such excited states a large angular moment, which when driven with circularly polarized light, translates to a large effective magnetic field ${B}_{\text{eff}}$. We calculate this effect to generate effective magnetic fields of $O(1\,μ\text{T})\times\left( \fracω{1\,\text{THz}} \right)^{-1} \left( \frac{I}{10\,\text{W cm}^{-2}} \right) n^4$ in the Rydberg states of atoms such as Rb and Cs for off-resonant photon beams with frequency omega and intensity ${I}$ expressed in units of the denominators and $n$ the principal quantum number. Additionally, terahertz spectroscopy of phosphorus doped silicon reveals a large cross-section for excitation of shallow dopants to Rydberg-like states, which even for small $n$ have the potential to be driven similarly with circularly polarized light to produce an even larger magnetization. Our theoretical calculations estimate ${B}_{\text{eff}}$ as $O(10^2\,\text{T})$ for Si:P with a beam intensity of $10^8\,\text{W cm}^{-2}$.

physics.atom-ph↗