Explorations of engineered bosonic systems in ultracold atoms, oscillator networks, quantum spin chains, and space

Rhyno, Brendan Douglas

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https://hdl.handle.net/2142/127207 Copy

Description

Title

Explorations of engineered bosonic systems in ultracold atoms, oscillator networks, quantum spin chains, and space

Author(s)

Rhyno, Brendan Douglas

Issue Date

2024-11-22

Director of Research (if dissertation) or Advisor (if thesis)

Vishveshwara, Smitha

Doctoral Committee Chair(s)

Stone, Michael

Committee Member(s)

• Gadway, Bryce
• Witek, Helvi

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Bose-Einstein condensates
• ultracold bubbles
• Cold Atom Laboratory
• analog gravity
• analog cosmology
• synthetic mechanical lattices
• quantum computing
• quantum simulation
• Kibble-Zurek mechanism

Abstract

Bosons represent one of the fundamental building blocks of nature, and not surprisingly they are responsible for much of the rich phenomena observed in physics. In this thesis, we probe but a few aspects of bosonic many-body systems as we explore three highly engineered experimental platforms. We begin by studying atomic Bose-Einstein condensates confined in shell-shaped or "bubble" geometries. This system offers a unique setting to investigate the consequences of curved space on collective phenomena. This work was performed in collaboration with our experimental colleagues who recently made the first observations of ultracold bubbles using the Cold Atom Laboratory aboard the International Space Station. Unique to these experiments is the perpetual free-fall environment provided by orbital microgravity, which allows novel atom trapping methods to be utilized to engineer large ultracold closed shell-like structures. Here, we outline our role in studying the properties of these quantum bubbles. In particular, our efforts to model the thermodynamic and dynamic properties of shell-shaped Bose-Einstein condensates is discussed. We then investigate the prospect of using a system composed of highly tunable feedback-coupled mechanical oscillators to simulate aspects of scalar field theories relevant to inflationary cosmology. Our work adds to the growing body of literature in the field of analog gravity, wherein one finds tunable experimental systems to realize some aspect of Einstein's theory of gravity. There are well-known analogies to gravitational physics using both classical and quantum fluids. Here, we show that the equations of motion for quantum fluctuations about a Bose-condensed inflaton field in a background Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime can naturally be simulated with classical coupled harmonic oscillators, provided their interactions can be tuned via measurement based feedback. Utilizing such a synthetic mechanical lattice, we provide a proof-of-principle experimental demonstration of analog cosmology simulating different expanding background FLRW spacetimes. We finish with a discussion on the nontrivial spectral properties of a class of quadratic bosonic Hamiltonians that can arise in cosmological scenarios. Finally, we consider one-dimensional strongly interacting spinless lattice bosons and the emergent physical description in terms of pseudo spin-1/2 degrees of freedom. We then explore simulating the many-body dynamics of these quantum spin chains using digital quantum computers and outline a procedure to carry out such simulations. In particular, utilizing IBM Quantum hardware, we experimentally simulate the dynamics of more than 100 qubits initialized in the paramagnetic ground state of the one-dimensional transverse field Ising model and linearly quench the system towards its quantum critical point. Upon finding deviations from the universal scaling predictions of the quantum Kibble-Zurek mechanism, we consider quench dynamics in the presence of noise. As a concrete example, we examine decoherence brought about by quantum nondemolition measurements of the instantaneous Hamiltonian and find numeric evidence for modified critical scaling.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127207

Copyright and License Information

Copyright 2024 Brendan Rhyno

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