Persistent current formation in double-ring geometries (1911.12802v3)

Abstract: Quenching an ultracold bosonic gas in a ring across the Bose-Einstein condensation phase transition is known, and has been experimentally observed, to lead to the spontaneous emergence of persistent currents. The present work examines how these phenomena generalize to a system of two experimentally accessible explicitly two-dimensional co-planar rings with a common interface, or to the related lemniscate geometry, and demonstrates an emerging independence of winding numbers across the rings, which can exhibit flow both in the same and in opposite directions. The observed persistence of such findings in the presence of dissipative coupled evolution due to the local character of the domain formation across the phase transition and topological protection of the randomly emerging winding numbers should be within current experimental reach.

• The paper demonstrates that persistent currents form in double-ring geometries during the Bose-Einstein condensation phase transition, highlighting the independence of winding numbers across rings.
• It applies the stochastic projected Gross-Pitaevskii equation to model dynamics, showing that geometric variations like lemniscate configurations maintain robust supercurrent formation.
• The findings suggest promising atomtronic applications, as stable, isolated supercurrents could advance coherent circuit designs in quantum technologies.

Overview of "Persistent current formation in double-ring geometries"

The study conducted by T. Bland et al. explores the phenomenon of persistent current formation in ultracold bosonic gases when quenched across the Bose-Einstein condensation (BEC) phase transition. Unlike previous works that have been confined to single-ring geometries, this paper expands the investigation into more complex two-dimensional configurations, specifically focusing on double-ring geometries and lemniscate shapes which present unique potential applications in atomtronics.

Research Context and Methodology

In the context of a second-order phase transition and spontaneous symmetry breaking, this research utilizes the stochastic projected Gross-Pitaevskii equation (SPGPE) as the foundation for modeling the dynamics in the formation of persistent currents. Through a comprehensive exploration using simulations, the team has expanded the traditional understanding, often constrained to single-ring setups, into double-ring environments where two coplanar rings share a common interface. This configuration is akin to the Mooij-Harmans qubit model, a superconducting system of interest for quantum computing applications.

Key Findings

1. Independence of Winding Numbers: One of the noteworthy findings from this study is the emerging independence of the winding numbers across the rings. The results demonstrate that the supercurrents in each ring are largely unaffected by the proximity and interaction with the neighboring ring. This lack of correlation in the winding numbers across the rings suggests that the domain formation during the phase transition maintains local characteristics within each ring.
2. Robustness in Different Geometries: The observations hold robust across different two-ring geometries, including lemniscate configurations. This suggests that these geometric variations do not significantly alter the fundamental process of persistent current formation, but rather support the isolated development of winding numbers within each ring.
3. Experimental Realization and Applications: Given the theoretical simulations indicate that the persistent currents are strong and stable in these configurations, they are positioned as feasible candidates for experimental validation. The implications for atomtronics are particularly compelling, as the control over such currents can lead to advancements in coherent atomtronic circuits, which mirror electronic circuits using neutral atoms.

Practical and Theoretical Implications

The study's implications extend into multiple domains, notably quantum technology and information systems. The ability to generate and control supercurrents opens pathways for constructing robust atomtronic devices, which have the potential to outpace traditional electronic systems in terms of coherence and precision. On a theoretical level, understanding the dynamics of phase transition in more complex systems contributes significantly to the refinement of models governing critical phenomena and phase transition dynamics.

Future Developments

The findings invite further exploration on controlling the tunneling and coupling of supercurrent states between rings, paving the way for advanced atomtronic devices. This could ultimately lead to more sophisticated qubit designs influenced by this qubit-like behavior in atomic systems. Additionally, experimental verification remains a crucial step to validate the theoretical predictions and facilitate the transition of these insights into practical, empirically supported applications.

In conclusion, the paper by Bland et al. provides a significant contribution to the field of quantum gases, expanding current knowledge of supercurrent dynamics and offering a promising foundation for future advancements in atomtronics and quantum computing technologies.