arXiv subjects

Tomasz Sowiński

Publications and source records attributed to Tomasz Sowiński.

At least 19 recordsLinked to original sources

arXiv2026

Controlled dynamics of a multi-component discrete-time quantum walker

We investigate a discrete-time quantum walk of a three-component quantum particle on a one-dimensional lattice. As coin operators, we employ parameterized rotations generated by the Gell-Mann matrices, which enable systematic tuning of the couplings between the internal components. We analyze how these couplings influence and control the dynamics by systematically exploring the position-space probability distribution across a broad region of the parameter space. To quantify the impact of different inter-component couplings, we further examine the ratio of the mean position to the variance in each half of the lattice. Our results indicates that the system supports a rich variety of transport regimes, ranging from nearly symmetric, rapidly spreading walks to strongly anisotropic dynamics with partial localization. This framework thus provides a new avenue for engineering targeted spreading and trapping behavior in multicomponent discrete-time quantum walks.

quant-ph↗

arXiv2026

Quantum walker trapped by self-similarity of the Sierpiński carpet

We study the dynamics of a single quantum particle on a finite-size square lattice with a fractal structure resembling the Sierpiński carpet, and compare it to the dynamics on a uniform lattice of the same size. For a particle initially localized at a corner of the lattice, we monitor the probability of finding it near the initial and opposite corners using zone-integrated probabilities, allowing a consistent comparison across fractal orders. While on the uniform lattice the particle reaches the opposite corner ballistically, in a time proportional to the lattice size, on the Sierpiński lattice it becomes increasingly confined to the vicinity of its initial position. We show that this trapping builds up self-similarly across the whole hierarchy of corner zones of the lattice.

quant-ph↗

arXiv2026

Discrete time quantum walk of locally interacting walkers

In this work, we introduce a general form of a two-parameter family of local interactions between quantum walkers conditioned on the internal state of their coins. By choosing their particular case, we systematically study the impact of these interactions on the dynamics of two initially localized and noncorrelated walkers. Our general interaction framework, which reduces to several previously studied models as special cases, provides a versatile platform for engineering quantum correlations with applications in quantum simulation, state preparation, and sensing protocols. It also opens up the possibility of analyzing many-body interactions for larger numbers of walkers.

quant-ph↗

arXiv2026

Impurity immersed in a two-component few-fermion mixture in a one-dimensional harmonic trap

We investigate a one-dimensional three-component few-fermion mixture confined in a parabolic external trap, where one component contains a single particle acting as an impurity. Focusing on the many-body ground state, we analyze how the interactions between the impurity and the other components influence the system's structure. For fixed interaction strengths within the mixture, we identify a critical interaction strength with the impurity for which the system undergoes a structural transition characterized by a substantial change in its spatial features. We explore this transition from the point of view of correlations and ground-state susceptibility. We remarkably find that this transition exhibits unique universality features not previously observed in other systems, highlighting novel many-body properties existing in multi-component fermionic mixtures.

cond-mat.quant-gas↗

arXiv2025

Hierarchy of pairing in imbalanced three-component one-dimensional Fermi gas

We study a one-dimensional, three-component Fermi gas with population imbalance using the Bogoliubov-de Gennes mean-field approach. We specifically consider pairing in two channels while deliberately excluding the third by setting its interaction strength to zero. By systematically varying the interaction strength and population imbalance, we identify a rich set of spatially modulated superfluid states, including structures akin to the Larkin-Ovchinnikov phase and phase-separated domains. A clear hierarchy emerges in the pairing behavior, shaped by the competition between the local density of states and the Fermi momentum mismatch. A fidelity-based analysis of the density further distinguishes smooth crossovers from sharp spatial reorganizations. Our results shed light on how pairing symmetry and population imbalance determine the structure of spatially inhomogeneous superfluid phases in multicomponent systems with reduced dimensionality.

cond-mat.quant-gas↗

arXiv2025

Swinging small quantum systems out of available values of control parameters

When a quantum system is prepared in its many-body ground state, it can be adiabatically driven to another ground state by changing its control parameter. However, relying on adiabaticity is experimentally unjustified. Moreover, the target value of the control parameter may occur outside the experimentally accessible range. The indicated target state, however, can still be reached within a clever protocol of temporal changes of the control parameter provided its decomposition into some basis is known. It turns out that such a protocol can be obtained in the framework of the optimal control theory. In this paper, we show how to apply such an optimization scheme to small quantum systems treating interaction strength as the control parameter. We believe that the proposed approach can be creatively extended to various complex quantum systems.

quant-ph↗

arXiv2025

Stability conditions for bound states in antiprotonic atoms

We study the stability of bound antiprotons in close proximity to the atomic nucleus. Using experimental data from X-ray spectroscopy measurements of antiprotonic atom transitions, we tune a minimal theoretical framework and estimate parameter ranges where the strong or electromagnetic decay channels govern the stability of the deepest bound states. In this way, we present an overview of the dominant decay mechanism of antiprotonic orbits for a given principle quantum number, to assist future spectroscopic experiments on antiprotonic atoms.

physics.atom-ph↗

arXiv2024

Lissajous dynamics of a quantum particle in a tilted two-dimensional discrete lattice

The quantum dynamics of a single particle in a discrete two-dimensional tilted lattice is analyzed from the perspective of the classical-quantum correspondence. Utilizing the fact that tilting the lattice results in oscillatory dynamics, we show how the parameters of the lattice and the initial state of the particle can be tuned so that during evolution the probability distribution does not change its shape while its center follows the trajectory known in classical mechanics as Lissajous curves.

quant-ph↗

arXiv2024

Exploring Many-body Interactions Through Quantum Fisher Information

The investigation of many-body interactions holds significant importance in both quantum foundations and information. Hamiltonians coupling multiple particles at once, beyond others, can lead to a faster entanglement generation, multiqubit gate implementation and improved error correction. As an increasing number of quantum platforms enable the realization of such physical settings, it becomes interesting to study the verification of many-body interaction resources. In this work, we explore the possibility of higher-order couplings detection through the quantum Fisher information. For a family of symmetric and translationally invariant $k$-body Ising-like Hamiltonians, we derive the bounds on the quantum Fisher information in product states. Due to its ordering with respect to the order of interaction, we demonstrate the possibility of detecting many-body couplings for a given Hamiltonian from the discussed family by observing violations of an appropriate bound. As a possible extension to these observations, we further analyse an example concerning the three-body interaction detection in the XY model.

quant-ph↗

arXiv2024

Exact dynamics of two ultra-cold bosons confined in a one-dimensional double-well potential

The dynamics of two ultra-cold bosons confined in a one-dimensional double-well potential is studied. We compare the exact dynamics governed by a full two-body Hamiltonian with the dynamics obtained in a two-mode model approximation. We show that for sufficiently large interactions the two-mode model breaks down and higher single-particle states have to be taken into account to describe the dynamical properties of the system correctly.

cond-mat.quant-gas↗

arXiv2024

The spin-flip-induced quadrupole resonance in odd-$A$ exotic atoms

We examine the possible existence of quadrupole resonances in exotic atoms containing odd-$A$ nuclei. We find that the spin-flip of the de-exciting exotic particle can induce a resonance, altering the orbital angular momentum of the nucleus by one quanta. This process results in an excited nucleus with a suppression in x-ray photon emissions during the exotic atom cascade. We provide specific cases of antiprotonic atoms of stable elements where this resonance effect is expected to occur. The study of this phenomena may provide insight into the strong interaction of deeply bound antiprotonic states in the proximity of the unpaired nucleon, and serve as a tool for probing short-lived excited nuclear states.

physics.atom-ph↗

arXiv2024

CIRCUS: an autonomous control system for antimatter, atomic and quantum physics experiments

A powerful and robust control system is a crucial, often neglected, pillar of any modern, complex physics experiment that requires the management of a multitude of different devices and their precise time synchronisation. The AEgIS collaboration presents CIRCUS, a novel, autonomous control system optimised for time-critical experiments such as those at CERN's Antiproton Decelerator and, more broadly, in atomic and quantum physics research. Its setup is based on Sinara/ARTIQ and TALOS, integrating the ALPACA analysis pipeline, the last two developed entirely in AEgIS. It is suitable for strict synchronicity requirements and repeatable, automated operation of experiments, culminating in autonomous parameter optimisation via feedback from real-time data analysis. CIRCUS has been successfully deployed and tested in AEgIS; being experiment-agnostic and released open-source, other experiments can leverage its capabilities.

quant-ph↗

arXiv2023

Unconventional pairing in few-fermion systems at finite temperature

Attractively interacting two-component mixtures of fermionic particles confined in a one-dimensional harmonic trap are investigated. Properties of balanced and imbalanced systems are systematically explored with the exact diagonalization approach, focusing on the finite-temperature effects. Using single- and two-particle density distributions, specific non-classical pairing correlations are analyzed in terms of the noise correlations -- quantity directly accessible in state-of-the-art experiments with ultra-cold atoms. It is shown that along with increasing temperature, any imbalanced system hosting Fulde-Ferrel-Larkin-Ovchinnikov pairs crossovers to a standard Bardeen-Cooper-Schrieffer one characterized by zero net momentum of resulting pairs. By performing calculations for systems with different imbalances, the approximate boundary between the two phases on a phase diagram is determined.

cond-mat.quant-gas↗

arXiv2023

Universality of internal correlations of strongly interacting p-wave fermions in one-dimensional geometry

We consider the many-body ground state of polarized fermions interacting via zero-range $\mathfrak{p}$-wave forces in a one-dimensional geometry. We rigorously prove that in the limit of infinite attractions spectral properties of any-order reduced density matrix describing arbitrary subsystem are completely independent of the shape of an external potential. It means that quantum correlations between any two subsystems are in this limit insensitive to the confinement. In addition, we show that the purity of these matrices quantifying the amount of quantum correlations can be obtained analytically for any number of particles without diagonalizing them. This observation may serve as a rigorous benchmark for other models and methods describing strongly interacting p-wave fermions.

cond-mat.quant-gas↗

arXiv2022

Sudden quench of harmonically trapped mass-imbalanced fermions

Dynamical properties of two-component mass-imbalanced few-fermion systems confined in a one-dimensional harmonic trap following a sudden quench of interactions are studied. It is assumed that initially the system is prepared in the non-interacting ground state and then, after a sudden quench of interactions, the unitary evolution is governed by interacting many-body Hamiltonian. By careful analysis of the evolution of the Loschmidt echo, density distributions of the components, and entanglement entropy between them, the role of mass imbalance and particle number imbalance on the system's evolution stability are investigated. All the quantities studied manifest a dramatic dependence on the number of heavy and lighter fermions in each component at a given quench strength. The results may have implications for upcoming experiments on fermionic mixtures with a well-defined and small number of particles.

cond-mat.quant-gas↗

arXiv2022

Comment on "Do Bloch waves interfere with one another?"

We point out that argumentation presented in [Phys. Lett. A 417, 127699 (2021)], leading to the conclusion that in periodic systems there is a superselection principle forbidding two different Bloch states to form a coherent superposition of a fixed phase, is unjustified and false. As an example, we show that the operator projecting to the selected Wannier state can be experimentally utilized to determine relative phase between superposed Bloch states. In this way we argue that, in fact, the non-existence of the aforementioned superselection principle is manifested always when localized measurements are performed, for example in state-of-the-art experiments with ultracold atoms confined in optical lattices.

quant-ph↗

arXiv2022

Fundamental limitations of the eigenvalue continuation approach

In this work, we show that the eigenvalue continuation approach introduced recently in [Phys. Rev. Lett. {\bf 121}, 032501 (2018)], despite its many advantages, has some fundamental limitations which cannot be overcome when strongly correlated many-body systems are considered. Taking as a working example a very simple system of several fermionic particles confined in a harmonic trap we show that the eigenvector continuation is not able to go beyond the accuracy of the sampling states. We support this observation within a very simple three-level model capturing directly this obstacle. Since mentioned inaccuracy cannot be determined self-consistently within the eigenvalue continuation approach, support from other complementary methods is needed.

cond-mat.quant-gas↗

arXiv2022

Signatures of quantum chaos in low-energy mixtures of few fermions

The low energy dynamics of mesoscopic systems strongly depends on the presence of internal equilibration. For this reason, a better interpretation of ultracold atom experiments requires a more accurate understanding of how quantum chaos manifests itself in these systems. In this paper, we consider a simple but experimentally relevant one-dimensional system of a few ultracold fermions moving in a double-well potential. We analyze its many-body spectral properties, which are commonly used to trace quantum chaos. We observe some signatures of quantum chaos already in the system with three particles. Generally, these signatures become more pronounced when fermions are evenly added to both components. On the contrary, they become suppressed when the particle imbalance is increased.

cond-mat.quant-gas↗