Patterns in chaos have been directly observed in the quantum realm by an international team of researchers, led in part by UC Santa Cruz physicist Jairo Velasco, Jr. In a groundbreaking experiment published in Nature on November 27, the team confirmed a 40-year-old theoretical prediction: electrons confined in quantum space move along specific paths called “quantum scars” rather than scattering randomly as expected in chaotic systems.
Electrons, exhibiting both particle and wave-like behaviors, defy intuitive motion. Instead of rolling predictably like a ball, their movement can interfere with itself under certain conditions. This interference results in the concentration of electron paths into specific, high-density trajectories—known as “unique closed orbits.” These patterns are rare phenomena in quantum systems, predicted theoretically in 1984 by physicist Eric Heller but only now observed directly.
To achieve this, Velasco’s team used graphene, a two-dimensional material renowned for its exceptional quantum properties. They employed a scanning tunneling microscope (STM) to trap electrons and observe their behavior without disturbing the system. The STM’s finely tipped probe created a quantum “stadium” on the graphene surface, approximately 400 nanometers long, mimicking a confined environment where electrons could be studied in detail.
The experiment confirmed that within this stadium, electrons moved predictably along closed orbits rather than chaotically filling the space. This discovery has profound implications for quantum physics and practical applications in nanoelectronics. Velasco highlighted how maintaining electrons on defined paths preserves their quantum properties as they travel, which could revolutionize information processing. By nudging these orbits slightly, it may become possible to direct electrons predictably across devices, enhancing efficiency in transistors and other components.
Heller, a co-author of the study, described quantum scarring as a unique phenomenon that contrasts with classical chaos. In classical systems, particles moving in a confined space, like a billiard ball in a stadium-shaped table, bounce randomly and unpredictably, eventually covering all possible paths. However, in the quantum world, these orbits remain localized and are “remembered” indefinitely due to interference effects.
The experimental results offer direct visualization of quantum scars for the first time. Graduate student Zhehao Ge, the study’s first author, expressed enthusiasm for this breakthrough, noting its potential to deepen our understanding of chaotic quantum systems. The images captured by Velasco’s team provide a window into the quantum world, where chaos and order intertwine in unexpected ways.
This discovery opens the door to numerous applications. Transistors, already operating at the nanoscale, could become even more efficient by incorporating quantum scar designs. This advancement could lead to faster, more energy-efficient electronics, impacting technologies like computers, smartphones, and other devices reliant on dense transistor arrays.
Velasco and his colleagues also see potential in leveraging quantum scars to manipulate chaotic quantum phenomena. By harnessing these unique states, it may be possible to selectively and flexibly direct electron motion at the nanoscale, paving the way for new methods of quantum control and innovative devices.
The study, titled “Direct Visualization of Relativistic Quantum Scars in Graphene Quantum Dots,” involved contributions from a global team of researchers. Besides Velasco and Ge, the authors include Peter Polizogopoulos, Ryan Van Haren, and David Lederman from UC Santa Cruz; Anton Graf and Joonas Keski-Rahkonen from Harvard University; Sergey Slizovskiy and Vladimir Fal’ko from the University of Manchester; and Takashi Taniguchi and Kenji Watanabe from Japan’s National Institute for Materials Science.
This collaborative effort marks a significant milestone in quantum physics, offering a deeper understanding of how chaos manifests at the quantum level and unlocking pathways for technological innovations grounded in the behavior of electrons in confined spaces.