In 1951, the renowned physicist Julian Schwinger proposed an extraordinary theoretical phenomenon that has captivated the imagination of physicists and science enthusiasts alike. Schwinger theorized that applying a sufficiently strong uniform electric field to a vacuum would cause the spontaneous generation of electron-positron pairs, effectively conjuring matter from “nothing.” This groundbreaking idea rests on the principles of quantum tunneling, where particles can traverse energy barriers that classical physics would consider impenetrable. Yet despite its profound implications for quantum field theory and the fabric of reality, this Schwinger effect remains experimentally elusive due to the extreme magnitude of electric fields required—far beyond the reach of contemporary laboratory apparatus.
The practical barriers to observing the Schwinger effect have long anchored it firmly in the realm of theory. Estimates suggest that electric fields on the order of 10^18 volts per meter or higher are necessary to induce such vacuum pair production—a scale that challenges the limits of current high-energy physics facilities. This absence of empirical verification sparked a new line of inquiry among theorists at the University of British Columbia (UBC), who sought to circumvent the towering technological hurdles by devising an analogous system more amenable to direct observation. Their innovative approach replaces the vacuum with a thin film of superfluid helium and substitutes the homogenous electric field with a background flow within the superfluid, creating a parallel effect that retains the fundamental physics but renders it experimentally accessible.
Superfluid Helium-4, a phase of helium cooled near absolute zero, displays remarkable quantum properties. When confined into films only a few atomic layers thick and cooled sufficiently, it essentially forms a frictionless quantum vacuum. Dr. Philip Stamp, a leading theorist at UBC, explains the significance of this state: “Superfluid Helium-4 is a wonder. At a few atomic layers thick, it can be cooled very easily to a temperature where it’s basically in a frictionless vacuum state.” This unique environment mimics key characteristics of the vacuum in quantum field theory, allowing the researchers to translate the Schwinger effect into the realm of condensed matter physics. Instead of electron-positron pairs emerging from nothingness, this superfluid system predicts the spontaneous formation of vortex/anti-vortex pairs—quantized whirlpools of superfluid circulation spinning in opposite directions.
The mathematics underlying these vortex phenomena is deeply intertwined with the physics of quantum tunneling. Dr. Stamp and his collaborator, Michael Desrochers, have formulated a robust theoretical framework describing how these vortex pairs form spontaneously as a result of the superfluid’s flow. Their model bridges abstract quantum field theory with tangible experimentation, allowing researchers to probe vacuum-like behavior without constructing unfeasible setups. Crucially, their paper, recently published in Proceedings of the National Academy of Sciences, outlines a detailed pathway for laboratory experiments that could conclusively detect and characterize these vortex tunneling events.
Quantum vacuum tunneling holds a central place in modern physics, offering insights into processes from particle physics to cosmology. Contrary to intuition, vacuum states in quantum theory are not empty voids but dynamic fields bubbling with transient virtual particles that flicker into and out of existence. Dr. Stamp articulates the profound analogy embodied in their work, stating, “We believe the Helium-4 film provides a nice analog to several cosmic phenomena.” This includes the quantum vacuum permeating deep space, the enigmatic quantum aspects of black holes, and even the nascent moments following the Big Bang—phenomena otherwise inaccessible due to insurmountable scale or energy requirements.
While analogies always carry caveats—no replica can capture every nuance of the original—this research emphasizes the dual utility of the experiment. Beyond serving as a proxy for inaccessible cosmic phenomena, it reshapes our fundamental understanding of superfluid dynamics and phase transitions in two-dimensional quantum systems. “These are real physical systems in their own right, not analogs. And we can do experiments on these,” Dr. Stamp stresses, highlighting the broad implications for condensed matter physics and quantum turbulence research.
One of the pivotal breakthroughs in Stamp and Desrochers’ theory stems from a revised understanding of vortex mass. Traditional approaches often treat the mass of vortices within superfluids as a fixed constant, simplifying their behavior. However, the UBC team reveals that this mass is in fact highly variable, fluctuating dramatically as vortices move through the superfluid film. This discovery challenges long-standing assumptions and compels a re-examination of how vortices interact with their environment, both in condensed matter physics and potentially in the context of the early universe’s quantum fields.
Michael Desrochers highlights the excitement surrounding this finding: “It’s exciting to understand how and why the mass varies, and how this affects our understanding of quantum tunneling processes, which are ubiquitous in physics, chemistry and biology.” This insight not only deepens our grasp of superfluid vortex dynamics but also suggests possible modifications to canonical models of quantum tunneling across disciplines. The mass variability could influence reaction rates, coherence phenomena, and transport properties in various quantum materials.
Intriguingly, Stamp posits that the variable vortex mass discovered in their superfluid analog may have direct implications for the original Schwinger effect involving electron-positron pairs. “The same mass variability will occur with electron-positron pairs in the Schwinger effect,” he argues, implying that Schwinger’s original theoretical framework might require refinement. This concept, whimsically dubbed the ‘revenge of the analog,’ underscores how insights gained from condensed matter systems can reverberate back into fundamental particle physics, fostering a virtuous cycle of discovery across disciplines.
The broader impact of this work extends beyond the immediate experimental ambitions. By providing a workable platform to study vacuum tunneling phenomena experimentally, the research opens new vistas for exploring non-equilibrium quantum phase transitions, topological excitations, and emergent quantum coherence. Moreover, it offers a promising bridge between quantum gravity concepts and laboratory physics, bringing abstract theoretical conjectures closer to empirical testing.
Support for this pioneering research came from the National Science and Engineering Research Council, underscoring the importance of foundational science in advancing both knowledge and technological capability. The collaboration and cross-pollination of ideas between condensed matter physics and high-energy theory exemplify the interdisciplinary spirit driving modern physics. As further experiments validate and extend these predictions, we may soon witness a radical expansion in our ability to manipulate and understand quantum vacuum phenomena in controlled settings.
In sum, the University of British Columbia team’s innovative reinterpretation of the Schwinger effect through the lens of superfluid helium films represents a milestone in quantum physics research. It transcends traditional boundaries by pairing elegant theoretical insights with practical experimental designs, unlocking new pathways to probe the elusive frontier where quantum mechanics, particle physics, and cosmology converge. These findings not only enrich our fundamental comprehension of the vacuum and quantum tunneling but also underscore the transformative potential of analog research systems in illuminating the mysteries of the universe.
Subject of Research: Not applicable
Article Title: Vacuum Tunneling of Vortices in 2-Dimensional 4He Superfluid Films
News Publication Date: 1-Sep-2025
Web References:
10.1073/pnas.2421273122
Keywords
Quantum tunneling, Quantum mechanics, Physics
