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DTSTART:20250527T080000Z
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LOCATION:ICFO Auditorium and Online (Teams)
SUMMARY:ICFO | BARBARA ANDRADE DOS SANTOS
CLASS:PUBLIC
DESCRIPTION:This is a thesis in theoretical physics about analog quantum si
 mulations\, digital quantum simulations (quantum computing)\, and quantum 
 state preparation using different quantum platforms (neutral atoms\, trapp
 ed ions\, and superconducting circuits). We live in a quantum era with suc
 h a wide variety of platforms available\, however performing experiments o
 n existing quantum devices remains challenging due to limitations in contr
 ol\, scale\, and connectivity. Therefore\, innovative strategies must be d
 eveloped to achieve quantum advantage using current quantum technology. We
  are primarily interested in applications to high-energy physics\, as quan
 tum computing provides a natural framework for simulating the real-time ev
 olution of gauge theories. While the field of quantum simulations and quan
 tum computing is still in its infancy and may be far from uncovering relev
 ant insights about the Standard Model in regimes inaccessible to analytica
 l methods\, classical simulations\, or direct experiments\, interesting di
 scoveries are emerging. Significant developments include the observation o
 f quantum many-body scar states and the reformulation of quantum field the
 ories as quantum link models.&nbsp\;\nMost part of the thesis is dedicated
  to the quantum simulations of lattice gauge theories\, which we explore u
 nder different lenses. First\, we propose a scheme to effectively generate
  three body interactions in trapped-ion platforms which consists of a gene
 ralization of the M&oslash\;lmer-S&oslash\;rensen scheme for three spins. 
 In this project\, we envision the quantum simulation of the spin 1/2 quant
 um link model description of the massless Schwinger model\, which features
  a three-body interaction. Such interaction requires at least 12 two-qubit
  gates to be performed\, which in principle accumulates more errors than a
  single three-qubit gate. This is what makes analog quantum simulations so
  powerful: We can tailor the platform to generate interactions of a specif
 ic target model\, potentially reducing quantum errors.&nbsp\;\nNext\, assu
 ming the existence of a perfect three-body gate\, we study quantum many-bo
 dy scar states in the Schwinger model. We use a mapping from the spin 1/2 
 Schwinger quantum link model to the PXP model to identify the relevant phy
 sical configurations. Then\, we compare the evolution of thermal and non-t
 hermal states under sequential Trotterized quantum circuits to their evolu
 tion under randomized quantum circuits. Our results indicate that the non-
 thermal sector of the Hilbert space\, which includes the quantum many-body
  scars\, are more sensitive to randomization.&nbsp\;\nThen\, on a more rea
 listic note\, we use real quantum devices from IBMQ to perform digital qua
 ntum simulations of the Schwinger model. These quantum computers are based
  on superconducting circuits\, and we currently have access to up to 156-q
 ubits together with a basis of single and two-qubit gates. The devices imp
 ose strong limitations on connectivity and depth of the quantum circuits\,
  hence we propose using gauge invariance\, in the form of the Gauss' law\,
  for quantum error detection.\nIn the last part of this thesis\, we shift 
 focus to study an interesting many-body behavior that emerges from the pre
 sence of a static gauge field. Specifically\, we propose a protocol for th
 e quasi-adiabatic preparation of the 1/2-Laughlin state\, a fractional qua
 ntum Hall state\, using rotating ultracold atoms to create artificial gaug
 e fields. From the condensate phase to the Laughlin state there are three 
 points of closed gaps\, and we make trap largely anisotropic to cross thes
 e regions without losing fidelity. We improved the preparation times by a 
 factor of ten compared to previous studies.\nTuesday May 27\, 10:00 h. ICF
 O Auditorium \nThesis Directors: Prof. Dr. Maciej Lewenstein and Dr. Tobia
 s Daniel Grass.
DTSTAMP:20260407T073357Z
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