Can Elementary Particles Create Light-Based Atoms?

Introduction

For centuries, the atom has been the fundamental unit of matter, with its nucleus and electrons defining its unique properties. However, the field of quantum physics has opened new possibilities, leading researchers to consider if elementary particles can mimic this structure. Specifically, the concept of photonic atoms, where photons form a bound state, has emerged as a fascinating area of study. Can photons, which have zero rest mass, be made to behave like atoms, potentially leading to the creation of light-based matter? This article explores this exciting frontier in quantum physics, focusing on recent research in the form of attractive photons in a quantum nonlinear medium.

Can Anything Similar to Atoms Be Created?

Traditionally, the structure of an atom relies on its nucleus and electrons to maintain stability. Without a nucleus, an electron-like particle cannot orbit around a stable core, leading to instability. Additionally, balancing the strong nuclear force, which holds nucleons together, is not applicable in the absence of mass. Therefore, creating something similar to an atom with elementary particles alone remains challenging.

Theoretical and Experimental Advancements

A groundbreaking paper published in Nature in September 2013 validates the concept of building things with light. Photons, being massless particles, can be induced to behave as if they have mass through strong nonlinear interactions. This phenomenon, which has profound implications for quantum computing and photonics, relies on creating a bound state of photons.

The researchers achieved this in a fascinating experiment. They used linearly polarized, weak laser beams, near a transition frequency, to interact with a cold rubidium gas. By driving a control laser near a different transition, they generated strong nonlinear interactions between σ-polarized photons. These interactions are detected using photon-photon correlation functions, providing insights into the formation of a structured state. The transmission spectra and phase shifts were analyzed under different polarization bases, confirming the creation of a two-photon bound state.

Key Results

Photon bunching: The photon-photon correlation functions showed evidence of photon bunching, indicative of a two-photon bound state. Theoretical vs. Experimental Comparison: The experiment's results were compared with theoretical predictions, showing a close match for a bound state width of 2rB. Initial Wavefunction: The initial wavefunction, formψ 1, consisted of a bound state and superimposed scattering states, forming a coherent wavefunction.

This experiment confirms that photons can indeed form a bound state, reminiscent of an atom, albeit in a quantum nonlinear medium. The formation of this structured state is a significant step toward the creation of photonic atoms.

Further Exploration: Attractive Photons

The paper titled "Attractive Photons in a Quantum Nonlinear Medium" further investigates the phenomenon of photons forming a bound state. In this study, scientists from Harvard and MIT have created a novel form of matter by introducing attractive photons within a quantum nonlinear medium. These attractive photons exhibit behaviors analogous to atomic orbitals, suggesting the potential for creating light-based atom-like structures.

The creation of attractive photons is not merely an academic exercise. It opens up new avenues for quantum computing, enabling deterministic photonic quantum logic gates and all-optical switching. The ability to manipulate light particles in such a structured form could revolutionize data processing and communication technologies.

Conclusion

While traditional atoms rely on a nucleus and electrons for stability, recent research suggests that photons, through strong nonlinear interactions and quantum entanglement, can be made to behave as if they have mass. This has led to the concept of photonic atoms and the creation of new forms of matter through attractive photons in quantum nonlinear media. As this field continues to evolve, the implications for quantum information science and technology are vast and exciting.