Topological Optical Skyrmion Transfer to Matter

Quantum Physics Optics Condensed Matter Physics Physics
Topological Photonics Skyrmions Cold Atom Gas Data Storage Optical Topology

Academic Background

In recent years, structured light has demonstrated great potential in simulating topological skyrmion textures encountered in high-energy physics, cosmology, magnetic materials, and superfluids. Skyrmions are non-singular, localized topological structures initially proposed in nuclear physics and later extensively studied in superfluids, magnetic materials, and Bose-Einstein condensates. Although optical skyrmions hold potential applications in data encoding and storage, research on the transfer and storage of their topological structures to matter has been very limited. This paper aims to address this issue by experimentally demonstrating the high-fidelity mapping of skyrmion topology from a laser beam onto a gas of cold atoms, where it is detected in a new non-propagating form.

Source of the Paper

This paper is co-authored by Chirantan Mitra, Chetan Sriram Madasu, Lucas Gabardos, Chang Chi Kwong, Yijie Shen, Janne Ruostekoski, and David Wilkowski. The authors are affiliated with multiple research institutions, including Nanyang Technological University (Singapore), National University of Singapore (Singapore), Université Côte d’Azur (France), and Lancaster University (United Kingdom). The research was published on April 16, 2025, in the journal APL Photonics, titled “Topological Optical Skyrmion Transfer to Matter.”

Research Process

1. Preparation and Measurement of Optical Skyrmions

The first step of the research involved preparing and measuring the topological skyrmion texture in a laser beam. By superimposing a Gaussian beam with a Laguerre-Gaussian (LG) beam, a beam with a skyrmion topological structure was generated. The topological charge of the skyrmion was characterized using the Stokes vector, and the experimentally measured topological charge of the optical skyrmion was ( q \simeq 0.91 ).

2. Interaction of Optical Skyrmions with Cold Atoms

Next, the researchers allowed the optical skyrmion to interact with a gas of cold atoms. The experiment used a cold gas of strontium-87 atoms, controlled at a temperature of 6.9 microkelvin (μK). Through a λ-scheme energy level structure, the topological structure of the optical skyrmion was transferred to the atomic gas. Specifically, the Gaussian beam and the LG beam drove the transitions between two ground states and an excited state of the atoms, respectively, and the atoms were transferred from the initial state to a dark state via adiabatic passage.

3. Detection of Atomic Skyrmions

In the atomic gas, the topological structure of the skyrmion was characterized by detecting the population of the atomic dark state. The researchers used spin-sensitive shadow imaging techniques to measure the population distribution of the two ground states and extracted the topological charge density from it. The experimentally measured topological charge of the atomic skyrmion was ( q \simeq 0.84 ), slightly lower than that of the optical skyrmion, primarily due to the laser beam width being significantly larger than the size of the atomic cloud.

Main Results

  1. Topological Charge of the Optical Skyrmion: The experimentally measured topological charge of the optical skyrmion was ( q \simeq 0.91 ), indicating that its Stokes vector almost completely wrapped around the Poincaré sphere once.
  2. Topological Charge of the Atomic Skyrmion: In the atomic gas, the topological charge of the skyrmion was ( q \simeq 0.84 ), indicating that the topological structure maintained high fidelity during the transfer process.
  3. Difference in Topological Charges: The topological charge of the atomic skyrmion was slightly lower than that of the optical skyrmion, mainly due to the limited spatial overlap region between the laser beam and the atomic cloud, resulting in partial loss of topological information.

Conclusions and Significance

This study successfully achieved the high-fidelity transfer of optical skyrmion topology to a gas of cold atoms and, for the first time, detected the topological charge of skyrmions in atomic gas. This achievement provides new pathways for the storage and analysis of topological photonic states, particularly in the fields of data encoding and storage. Additionally, this research offers new experimental methods for studying more complex topologies in structured light.

Research Highlights

  1. High-Fidelity Topological Transfer: For the first time, the high-fidelity transfer of optical skyrmion topology to matter was achieved, and the topological charge of atomic skyrmions was successfully detected.
  2. Innovative Experimental Methods: The optical skyrmion was transferred to the atomic gas via adiabatic passage, and the topological structure was detected using spin-sensitive shadow imaging techniques.
  3. Potential Application Value: This research provides a new experimental foundation for the storage of topological photonic states and the analysis of complex topologies, holding significant scientific and application value.

Other Valuable Information

The experimental data from this study have been made publicly available on the Dataverse platform, and readers can access it via the DOI 10.21979/N9/EAVRTG. Additionally, the research team provided detailed descriptions of the atomic samples, beam generation, and measurement methods used in the experiment, offering important references for follow-up studies.

Through this research, scientists have not only demonstrated the feasibility of transferring optical skyrmions to matter but also opened new directions for future studies in topological photonics. This achievement is expected to have a profound impact in fields such as quantum information processing, data storage, and complex light field analysis.