Thomas Bilitewski

Oklahoma State University | Oklahoma State · Department of Physics

We experimentally and theoretically demonstrate spinor gases driven by spin-flopping fields are excellent platforms for investigating ergodicity breaking and quantum scarring. We observe that specific initial states remain nonthermal at weak driving despite the majority of states thermalizing, which constitutes clear evidence of quantum many-body s...

We investigate the quantum many-body dynamics of bosonic atoms hopping in a two-leg ladder with strong on-site contact interactions. We observe that when the atoms are prepared in a staggered pattern with pairs of atoms on every other rung, singlon defects, i.e.~rungs with only one atom, can localize due to an emergent topological model, even thoug...

Ultracold dipolar particles pinned in optical lattices or tweezers provide an excellent platform for the study of the intriguing equilibration dynamics of spin models with dipolar exchange. Starting with an initial state in which spins of opposite orientation are prepared in each of the legs of a ladder lattice, we show that spin relaxation display...

We study the non-equilibrium dynamics of a quantum spin 1/2 XXZ model confined in a two-dimensional bi-layer system, with couplings mediated by inverse power-law interactions, falling offwith distance r as 1/r^α, with spatio-temporal control of the spins enabled via local fields. An initial state of spins with opposite magnetization in the two laye...

We study the non-equilibrium dynamics of a quantum spin 1/2 XXZ model confined in a two-dimensional bi-layer system, with couplings mediated by inverse power-law interactions, falling off with distance r as 1/r α , and spatio-temporal control of the spins enabled via local fields. An initial state of spins with opposite magnetization in the two lay...

Entangled spin squeezed states generated via dipolar interactions in lattice models provide unique opportunities for quantum enhanced sensing and are now within reach of current experiments. A critical question in this context is which parameter regimes offer the best prospects under realistic conditions. Light scattering in deep lattices can induc...

The nonequilibrium dynamics of domain wall initial states in a classical anisotropic Heisenberg chain exhibits a striking coexistence of apparently linear and nonlinear behaviors: the propagation and spreading of the domain wall can be captured quantitatively by , i.e., noninteracting, spin wave theory absent its usual justifications; while, simult...

We study the nonequilibrium dynamics of dipoles confined in multiple stacked two-dimensional layers realizing a long-range interacting quantum spin 1/2 XXX model. We demonstrate that strong in-plane interactions can protect a manifold of collective layer dynamics. This then allows us to map the many-body spin dynamics to bosonic models. In a bilaye...

We study the temporal growth and spatial propagation of quantum correlations in a two-dimensional bilayer realizing a spin-1/2 quantum XXZ model with couplings mediated by long-range and anisotropic dipolar interactions. Starting with an initial state consisting of spins with opposite magnetization in each of the layers, we predict a dynamic instab...

The non-equilibrium dynamics of domain wall initial states in a classical anisotropic Heisenberg chain exhibits a striking coexistence of apparently linear and non-linear behaviours: the propagation and spreading of the domain wall can be captured quantitatively by \textit{linear}, i.e. non-interacting, spin wave theory absent its usual justificati...

We study the temporal growth and spatial propagation of quantum correlations in a two-dimensional bilayer realising a spin-1/2 quantum XXZ model with couplings mediated by long-range and anisotropic dipolar interactions. Starting with an initial state consisting of spins with opposite magnetization in each of the layers, we predict the emergence of...

Exchange-antisymmetric pair wavefunctions in fermionic systems can give rise to unconventional superconductors and superfluids1–3. The realization of these states in controllable quantum systems, such as ultracold gases, could enable new types of quantum simulations4–8, topological quantum gates9–11 and exotic few-body states12–15. However, p-wave...

Entangled spin squeezed states generated via dipolar interactions in lattice models provide unique opportunities for quantum enhanced sensing and are now within reach of current experiments. A critical question in this context is which parameter regimes offer the best prospects under realistic conditions. Light scattering in deep lattices can induc...

Motivated by the Kardar-Parisi-Zhang (KPZ) scaling recently observed in the classical ferromagnetic Heisenberg chain, we investigate the role of solitonic excitations in this model. We find that the Heisenberg chain, although well known to be nonintegrable, supports a two-parameter family of long-lived solitons. We connect these to the exact solito...

We study the non-equilibrium dynamics of dipoles confined in multiple stacked two-dimensional layers realising a long-range interacting quantum spin 1/2 XXZ model. We demonstrate that strong in-plane XXX interactions can protect a manifold of collective layer dynamics. This then allows us to map the many-body spin dynamics to bosonic models. In a b...

We theoretically study the dynamics of n-level spin-orbit coupled alkaline-earth fermionic atoms with SU(n) symmetric interactions. We consider three-dimensional lattices with tunneling along one dimension, and the internal levels treated as a synthetic dimension, realizing an n-leg flux ladder. Laser driving is used to couple the internal levels a...

Motivated by the KPZ scaling recently observed in the classical ferromagnetic Heisenberg chain, we investigate the role of solitonic excitations in this model. We find that the Heisenberg chain, although well-known to be non-integrable, supports a two-parameter family of long-lived solitons. We connect these to the exact soliton solutions of the in...

Exchange-antisymmetric pair wavefunctions in fermionic systems can give rise to unconventional superconductors and superfluids with non-trivial transport properties. The realisation of these states in controllable quantum systems, such as ultracold gases, could enable new types of quantum simulations, topological quantum gates, and exotic few-body...

We theoretically study the dynamics of $n$-level spin-orbit coupled alkaline-earth fermionic atoms with SU($n$) symmetric interactions. We consider three dimensional lattices with tunneling along one dimension, and the internal levels treated as a synthetic dimension, realizing an $n$-leg flux ladder. Laser driving is used to couple the internal le...

Microscopic control over polar molecules with tunable interactions enables the realization of distinct quantum phenomena. Using an electric field gradient, we demonstrated layer-resolved state preparation and imaging of ultracold potassium-rubidium molecules confined to two-dimensional planes in an optical lattice. The rotational coherence was maxi...

The observation of Pauli blocking of atomic spontaneous decay via direct measurements of the atomic population requires the use of long-lived atomic gases where quantum statistics, atom recoil, and cooperative radiative processes are all relevant. We develop a theoretical framework capable of simultaneously accounting for all these effects in the m...

The search for departures from standard hydrodynamics in many-body systems has yielded a number of promising leads, especially in low dimensions. Here, we study one of the simplest classical interacting lattice models, the nearest-neighbor Heisenberg chain, with temperature as the tuning parameter. Our numerics expose strikingly different spin dyna...

Microscopic control over polar molecules with tunable interactions would enable realization of novel quantum phenomena. Using an applied electric field gradient, we demonstrate layer-resolved state preparation and imaging of ultracold potassium-rubidium molecules confined to two-dimensional planes in an optical lattice. The coherence time of rotati...

We consider the nonequilibrium orbital dynamics of spin-polarized ultracold fermions in the first excited band of an optical lattice. A specific lattice depth and filling configuration is designed to allow the px and py excited orbital degrees of freedom to act as a pseudospin. Starting from the full Hamiltonian for p-wave interactions in a periodi...

The search for departures from standard hydrodynamics in many-body systems has yielded a number of promising leads, especially in low dimension. Here we study one of the simplest classical interacting lattice models, the nearest-neighbour Heisenberg chain, with temperature as tuning parameter. Our numerics expose strikingly different spin dynamics...

The observation of Pauli blocking of atomic spontaneous decay via direct measurements of the atomic population requires the use of long-lived atomic gases where quantum statistics, atom recoil and cooperative radiative processes are all relevant. We develop a theoretical framework capable of simultaneously accounting for all these effects in a regi...

We study correlations, transport, and chaos in a Heisenberg magnet as a classical model many-body system. By varying temperature and dimensionality, we can tune between settings with and without symmetry breaking and accompanying collective modes or quasiparticles (spin waves) which in the limit of low temperatures become increasingly long-lived. C...

We introduce a protocol to observe p-wave interactions in ultracold fermionic atoms loaded in a three-dimensional optical lattice. Our scheme uses specific motionally excited band states to form an orbital subspace immune to band relaxation. A laser dressing is applied to reduce the differential kinetic energy of the orbital states and make their d...

Inspired by recent developments in the study of chaos in many-body systems, we construct a measure of local information spreading for a stochastic cellular automaton in the form of a spatiotemporally resolved Hamming distance. This decorrelator is a classical version of an out-of-time-order correlator studied in the context of quantum many-body sys...

We study a bulk fermionic dipolar molecular gas in the quantum degenerate regime confined in a two-dimensional geometry. Using two rotational states of the molecules, we encode a spin 1/2 degree of freedom. To describe the many-body spin dynamics of the molecules, we derive a long-range interacting XXZ model valid in the regime where motional degre...

Inspired by recent developments in the study of chaos in many-body systems, we construct a measure of local information spreading for a stochastic Cellular Automaton in the form of a spatiotemporally resolved Hamming distance. This decorrelator is a classical version of an Out-of-Time-Order Correlator studied in the context of quantum many-body sys...

A recent experiment [L. De Marco, G. Valtolina, K. Matsuda, W. G. Tobias, J. P. Covey, and J. Ye, A degenerate Fermi gas of polar molecules, Science 363, 853 (2019)] reported for the first time the preparation of a Fermi degenerate gas of polar molecules and observed a suppression of their chemical reaction rate compared to the one expected from a...

Many-body quantum systems can exhibit a striking degree of symmetry unparallelled in their classical counterparts. In real materials SU(N) symmetry is an idealization, but this symmetry is pristinely realized in fully controllable ultracold alkaline-earth atomic gases. Here, we study an SU(N)-symmetric Fermi liquid of 87Sr atoms, where N can be tun...

We study a bulk fermionic dipolar molecular gas in the quantum degenerate regime confined in a two-dimensional geometry. We consider two rotational states that encode a spin 1/2 degree of freedom. We derive a long-range interacting XXZ model describing the many-body spin dynamics of the molecules valid in the regime where motional degrees of freedo...

We study correlations, transport and chaos in a Heisenberg magnet as a classical model many-body system. By varying temperature and dimensionality, we can tune between settings with and without symmetry breaking and accompanying collective modes or quasiparticles. We analyse both conventional and out-of-time-ordered spin correlators (`decorrelators...

A recent experiment reported for the first time the preparation of a Fermi degenerate gas of polar molecules and observed a suppression of their chemical reaction rate compared to the one expected from a purely classical treatment. While it was hypothesized that the suppression in the ultracold regime had its roots in the Fermi statistics of the mo...

Many-body quantum systems can exhibit a striking degree of symmetry unparalleled by their classical counterparts. While in real materials SU($N$) symmetry is an idealization, this symmetry is pristinely realized in fully controllable ultracold alkaline-earth atomic gases. Here, we study an SU($N$)-symmetric Fermi liquid of $^{87}$Sr atoms, where $N...

We study the low temperature static and dynamical properties of the classical bond-disordered antiferromagnetic Heisenberg model on the kagome lattice. This model has recently been shown to host a new type of spin liquid exhibiting an exponentially large number of discrete ground states. Surprisingly, despite the rigidity of the ground states, we e...

We study the chaotic dynamics in a classical many-body system of interacting spins on the kagome lattice. We characterize many-body chaos via the butterfly effect as captured by an appropriate out-of-time-ordered commutator. Due to the emergence of a spin-liquid phase, the chaotic dynamics extends all the way to zero temperature. We thus determine...

We study two models of correlated bond and site disorder on the kagome lattice considering both translationally invariant and completely disordered systems. The models are shown to exhibit a perfectly flat ground-state band in the presence of disorder for which we provide exact analytic solutions. Whereas in one model the flat band remains gapped a...

We study the low temperature static and dynamical properties of the classical bond-disordered antiferromagnetic Heisenberg model on the kagome lattice. This model has recently been shown to host a new type of spin liquid exhibiting an exponentially large number of discrete ground states. Surprisingly, despite the rigidity of the groundstates, we es...

We study the low temperature static and dynamical properties of the classical bond-disordered antiferromagnetic Heisenberg model on the kagome lattice. This model has recently been shown to host a new type of spin liquid exhibiting an exponentially large number of discrete ground states. Surprisingly, despite the rigidity of the groundstates, we es...

We study two models of correlated bond-and site-disorder on the kagome lattice considering both translationally invariant and completely disordered systems. The models are shown to exhibit a perfectly flat ground state band in the presence of disorder for which we provide exact analytic solutions. Whereas in one model the flat band remains gapped a...

We study two models of correlated bond- and site-disorder on the kagome lattice considering both translationally invariant and completely disordered systems. The models are shown to exhibit a perfectly flat ground state band in the presence of disorder for which we provide exact analytic solutions. Whereas in one model the flat band remains gapped...

We study the chaotic dynamics in a classical many-body system of interacting spins on the kagome lattice. We characterise many-body chaos via the butterfly effect as captured by an appropriate out-of-time-ordered correlator. Due to the emergence of a spin liquid phase, the chaotic dynamics extends all the way to zero temperature. We thus determine...

We study the chaotic dynamics in a classical many-body system of interacting spins on the kagome lattice. We characterise many-body chaos via the butterfly effect as captured by an appropriate out-of-time-ordered correlator. Due to the emergence of a spin liquid phase, the chaotic dynamics extends all the way to zero temperature. We thus determine...

Magnetic remanence - found in bar magnets or magnetic storage devices - is probably the oldest and most ubiquitous phenomenon underpinning technological applications of magnetism. It is a macroscopic non-equilibrium phenomenon: a remanent magnetisation appears when a magnetic field is applied to an initially unmagnetised ferromagnet, and then taken...

We study a class of disordered continuous classical spin systems including the kagome Heisenberg magnet. While each term in its local Hamiltonian can be independently minimised, we find {\it discrete} degenerate ground states whose number grows exponentially with system size. These states do not exhibit zero-energy `excitations' characteristic of h...

We study a class of disordered continuous classical spin systems including the kagome Heisenberg magnet. While each term in its local Hamiltonian can be independently minimised, we find discrete degenerate ground states whose number grows exponentially with system size. These states do not exhibit zero-energy `excitations' characteristic of highly...

This thesis considers novel phenomena arising in the few and many-body physics of ultracold atomic gases. The specific models considered are motivated by recent experimental developments. A main focus will be the theoretical description of systems used in the simulation of artificial gauge fields via time-modulated tuning of system parameters and v...

There has been a long-standing goal to find ways to cause neutral atoms to experience synthetic gauge fields, extending the capabilities of ultracold gases as simulators of quantum many-body systems. Such gauge fields can mimic the effect of magnetic fields and generate topological energy bands. Recent proposals to generate synthetic gauge fields r...

We study the many-body phases of bosonic atoms with $\small \textit{N}$ internal states confined to a one-dimensional (1D) optical lattice under the influence of a synthetic magnetic field and strong repulsive interactions. The $\small \textit{N}$ internal states of the atoms are coupled via Raman transitions creating the synthetic magnetic field i...

We study the many-body phases of bosonic atoms with N internal states confined to a one-dimensional (1D) optical lattice under the influence of a synthetic magnetic field and strong repulsive interactions. The N internal states of the atoms are coupled via Raman transitions creating the synthetic magnetic field in the space of internal spin states...

We study the instabilities towards (exotic) superconductivity of mixtures of spin-$1/2$ fermions coupled to scalar bosons on a two-dimensional square lattice with the Dynamical-Cluster-Approximation (DCA) using a numerically exact continuous-time Monte-Carlo solver. The Bogoliubov bosons provide an effective phononic bath for the fermions and induc...

We study the recent Floquet-realisation of the Harper-Hofstadter model in a gas of cold bosonic atoms. We study in detail the scattering processes in this system in the weakly interacting regime due to the interplay of particle interactions and the explicit time dependence of the Floquet states that lead to band transitions and heating. We focus on...

Motivated by recent experimental implementations of artificial gauge fields for gases of cold atoms, we study the scattering properties of particles that are subjected to time-periodic Hamiltonians. Making use of Floquet theory, we focus on translationally invariant situations in which the single-particle dynamics can be described in terms of spati...

We study the effects of radial flows on Galactic chemical evolution. A simple analytic scheme is developed prescribing the coupling of infall from the intergalactic medium and radial flows within the disc based on angular momentum conservation. We show that model parameters are tightly constrained by the observed [Fe/H]-abundance gradient in the Ga...