Tunable cold-atom momentum space double wells for phase-sensitive measurements

As quantum technologies move from theoretical development to practical realization, experimental access to quantum nonlinearities and critical phenomena becomes essential for advancing applications in quantum sensing, computing, and networking. These capabilities are underpinned by the fundamental behaviors of quantum matter near phase transitions and as well as the nonlinear interactions associated with them. This work explores the interplay between tunable quantum criticality and nonlinear interactions in ultracold atomic momentum-state double wells engineered using a rubidium-87 Bose-Einstein condensate (BEC). We discuss the development of our single-cell BEC apparatus and the various techniques necessary for its construction. We then use it to experimentally investigate Bragg-coupled atomic momentum modes and observe signatures consistent with beyond-the-mean-field effects in a system exhibiting features characteristic of collective quantum magnetism. These results point toward the presence of tunable nonlinearities in momentum space and offer a pathway for exploring momentum-state squeezing as a tool for enhanced quantum sensing. In parallel, this work also identifies a conceptual correspondence between the momentum-space “double-well” structure observed in our BEC system and phase transitions in a distinct class of quantum materials: quantum critical crystals at cryogenic temperatures. This cross-platform analogy highlights the potential universality of quantum critical phenomena and underscores the broader relevance of our findings. The studies described in this work demonstrate that the controlled exploration of phase transitions and nonlinearities in cold atom systems not only provides insight into fundamental quantum many-body physics but also supports the development of quantum-enhanced technologies. The ability to engineer and probe phase-sensitive effects in a highly tunable and coherent systems opens new avenues for implementing precision sensors, robust quantum communication protocols, and complex computational operations. Ultimately, the synergy between quantum criticality and phase sensitive measurements facilitated by induced nonlinearities may serve as a foundational principle for the next generation of quantum devices.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Williams, Garrett R.

Contributors dc:contributor

• Gadway, Bryce
• DeMarco, Brian
• Cooper, Lance
• Goldschmidt, Elizabeth

• Lasers
• Atoms
• States
• Nonlinearities
• Quantum

Statement dc:rights

• Copyright 2025 Garrett Williams

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129926

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129926