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Triptych of quantum matter in one dimension: Playful constructions in theoretical and computational physics
Stockholm University, Faculty of Science, Department of Physics.ORCID iD: 0000-0003-2038-3419
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this compilation thesis, three different quantum mechanical systems are presented. All three have in common that they are one-dimensional quantum systems which, each in their own way, can be seen as analogous to other quantum systems. Chapter 2 is an introduction which takes on the ambitious task to guide the reader from standard quantum mechanical theory to the theory of condensed matter physics. In chapter 3 I present a theory for creating co- herent oscillations in the adiabatic eigenstates of time-periodic quantum systems. These are directly analogous to so-called Bloch oscillations which appear for electrons in periodical potentials which are subjected to a constant force. Chapter 4 concerns how phonon physics, in particular the Peierls instability, can be mimicked in systems of interacting ultacold quantum mechanical gases. In chapter 5, I present quantum mechanical circuits (circuit QED). We propose a circuit where the low-energy physics is analogous to a strongly interacting generalized spin chain, where the so-called superradiance directly correspond to a polarized Ising phase. 

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2023. , p. 132
Keywords [en]
Bloch oscillations, Peierls, adiabatic, diabatic, ultracold atoms, Bose-Fermi mixtures, phonon, cQED, superradiance, polarons, DMRG, MPS, Kosterlitz-Thouless, Wannier, Bloch, quantum phase transitions
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Research subject
Theoretical Physics
Identifiers
URN: urn:nbn:se:su:diva-215403ISBN: 978-91-8014-234-2 (print)ISBN: 978-91-8014-235-9 (electronic)OAI: oai:DiVA.org:su-215403DiVA, id: diva2:1742928
Public defence
2023-04-27, sal FB42, AlbaNova universitetscentrum, Roslagstullsbacken 21 and online via Zoom https://stockholmuniversity.zoom.us/j/62067309502, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Knut and Alice Wallenberg Foundation, 31001190Swedish Research Council, 31001189Available from: 2023-04-03 Created: 2023-03-13 Last updated: 2023-03-28Bibliographically approved
List of papers
1. Bloch-like energy oscillations
Open this publication in new window or tab >>Bloch-like energy oscillations
2018 (English)In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 98, no 5, article id 053820Article in journal (Refereed) Published
Abstract [en]

We identify a type of periodic evolution that appears in driven quantum systems. Provided that the instantaneous (adiabatic) energies are equidistant we show how such systems can be mapped to (time-dependent) tilted single-band lattice models. Having established this mapping, the dynamics can be understood in terms of Bloch oscillations in the instantaneous energy basis. In our lattice model the site-localized states are the adiabatic ones, and the Bloch oscillations manifest as a periodic repopulation among these states, or equivalently a periodic change in the system's instantaneous energy. Our predictions are confirmed by considering two different models: a driven harmonic oscillator and a Landau-Zener grid model. To strengthen the link between our energy Bloch oscillations and the original spatial Bloch oscillations we add a random disorder that breaks the translational invariance of the spectrum. This verifies that the oscillating evolution breaks down and instead turns into a diffusive spreading. Finally, we consider a trapped ion setup and demonstrate how the mechanism can be utilized to prepare motional cat state of the ion.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-162796 (URN)10.1103/PhysRevA.98.053820 (DOI)000450138600010 ()2-s2.0-85057049385 (Scopus ID)
Available from: 2018-12-27 Created: 2018-12-27 Last updated: 2023-03-13Bibliographically approved
2. Exploring phonon-like interactions in one-dimensional Bose-Fermi mixtures
Open this publication in new window or tab >>Exploring phonon-like interactions in one-dimensional Bose-Fermi mixtures
(English)Manuscript (preprint) (Other academic)
Abstract [en]

With the objective of simulating the physical behaviour of electrons moving in a dynamical background, we study a cold atomic Bose-Fermi mixture in an optical lattice potential felt only by the bosons. The bosons, assumed to be in the deep superfluid regime, inherit the periodicity of the optical lattice and subsequently act as a dynamical potential for the polarized fermions. Due to the atom-phonon interaction between the fermions and the condensate, the coupled system displays a Berezinskii-Kosterlitz-Thouless transition from a Luttinger liquid to a Peierls phase. For sufficiently strong Bose-Fermi interaction, however, the Peierls phase becomes unstable and is succeeded by either a collapsed or a separated phase. We find that the main role of the optical lattice amounts to stabilizing the Peierls phase. Furthermore, the presence of a confining harmonic trap leads to a rich physical behaviour beyond what is observed for either bosons or fermions separately trapped. In particular, for an attractive Bose-Fermi interaction, the insulating phase may develop a fermionic wedding-cake like configuration reflecting the dynamical nature of the underlying lattice potential. For repulsive interaction, on the other hand, we conclude that the trap destabilizes the Peierls phase and the two species separate. 

Keywords
ultracold atoms, optical lattices, Kosterlitz-Thouless, Bose-Fermi mixtures, Peierls
National Category
Condensed Matter Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:su:diva-215400 (URN)
Funder
Swedish Research Council, 31001189Knut and Alice Wallenberg Foundation, 31001190
Available from: 2023-03-13 Created: 2023-03-13 Last updated: 2023-03-13
3. Superradiance, bosonic Peierls distortion, and lattice gauge theory in a generalized Rabi-Hubbard chain
Open this publication in new window or tab >>Superradiance, bosonic Peierls distortion, and lattice gauge theory in a generalized Rabi-Hubbard chain
2020 (English)In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 102, no 6, article id 063711Article in journal (Refereed) Published
Abstract [en]

We investigate a one-dimensional Rabi-Hubbard type of model, arranged such that a quantum dot is sandwiched between every cavity. The role of the quantum dot is twofold, to transmit photons between neighboring cavities and simultaneously act as an effective photon nonlinearity. We consider three-level quantum dots in the A configuration, where the left and right leg couple exclusively to the left or right cavity. This noncommuting interaction leads to two highly entangled incompressible phases, separated by a second-order quantum phase transition; the degrees of freedom of the quantum dots can be viewed as a dynamical lattice for the photons which spontaneously breaks Z(2) symmetry due to a bosonic Peierls instability, leading to a phase with dimerized order. Additionally, we find a normal insulating phase and a superfluid phase that acts as a quantum many-body superradiant phase. In the superradiant phase, a Z(2) symmetry is broken and the phase transition falls within the universality class of the transverse-field Ising model. Finally, we show that the model can be interpreted as a Z(2) lattice gauge theory in the absence of a dipolar field on the lower qutrit levels.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-190664 (URN)10.1103/PhysRevA.102.063711 (DOI)000597808100012 ()
Available from: 2021-03-03 Created: 2021-03-03 Last updated: 2023-03-13Bibliographically approved

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