A groundbreaking technique called coherence maps has been developed by scientists to shed light on quantum phenomena. By employing these maps, researchers have gained valuable insights into the quantum mechanics underlying photosynthesis, the remarkable process utilized by plants and certain bacteria to convert sunlight into nourishment. This innovative technique, which provides a visual representation of a system’s quantum behavior, has enabled the scientific team to delve into the molecular structure responsible for capturing solar energy and transferring it to the site of a chemical reaction.
In the pursuit of comprehending the mechanisms at the core of photosynthesis, scientists have devised coherence maps—a visualization technique to unravel the enigmatic world of quantum mechanics. These maps have successfully elucidated the intricate process of energy transfer in photosynthesizing bacteria, offering a clear depiction of how solar energy is channeled from the external to the internal molecular ring of the light-harvesting complex.
Quantum systems have long been regarded as challenging to visualize, but researchers at the University of Illinois Urbana-Champaign have ingeniously developed an illustrative technique that presents quantum features in a user-friendly diagram known as a coherence map. These maps were employed by the researchers to investigate the quantum mechanisms underlying photosynthesis—the process through which plants and certain bacteria utilize sunlight to convert carbon dioxide and water into sustenance.
Nancy Makri, a chemistry professor at the University of Illinois Urbana-Champaign and the leader of the project, expressed her astonishment at the simplicity of coherence maps. She stated, “When dealing with nonintuitive quantum phenomena within complex processes like photosynthesis, interpreting theoretical calculations can be quite challenging. However, coherence maps provide a comprehensive snapshot that conveys all the necessary information.”
In a recent publication in The Journal of Physical Chemistry Letters, Makri’s research group applied coherence maps to reanalyze previous computer simulations of photosynthesizing bacteria, unveiling new insights. The researchers focused on studying the molecular complex responsible for “harvesting” sunlight, absorbing its energy, and transferring it to a site where carbon dioxide and water undergo chemical reactions. The coherence maps not only clearly depicted the transfer of energy to the reaction site but also provided a profound quantum explanation for this process.
The work of Makri’s group was featured on the cover of The Journal of Physical Chemistry Letters. The cover art displayed a diagram of the bacterial light-harvesting complex juxtaposed with a coherence map, showcasing the quantum behaviors of the complex.
Makri explained that coherence maps represent the reduced density matrix, a mathematical entity that encompasses all the information regarding a system’s quantum behavior. She emphasized, “Even for moderately sized systems, the reduced density matrix becomes quite large, with interconnected components that are challenging to analyze. However, coherence maps simplify this complexity, revealing a wealth of information at a glance.”
This wealth of information empowered the researchers to transparently identify the pathways of energy transfer within the bacterial light-harvesting complex, as stated by Makri. This complex comprises an outer ring and an inner ring of molecules. While the outer ring absorbs sunlight, the inner ring houses the chemical reaction site. Makri’s group demonstrated that the motion of atoms within the molecules connects these two rings, and coherence maps vividly illustrated how this motion focuses energy from the outer ring to the inner ring.
Looking towards the future, Makri firmly believes that coherence maps will prove to be invaluable tools for theoretical analyses rooted in quantum mechanics. She added, “Just in this study, coherence maps provided crucial insights into the mechanism of photosynthesis, which has long been one of biology’s greatest mysteries.”
Makri’s research group published their simulations of the energy transfer mechanism in photosynthesizing bacteria in Science Advances, and they introduced coherence maps in The Journal of Physical Chemistry B.
References:
- “Coherence Maps and Flow of Excitation Energy in the Bacterial Light Harvesting Complex 2” by Reshmi Dani, Sohang Kundu, and Nancy Makri, 17 April 2023, The Journal of Physical Chemistry Letters. DOI: 10.1021/acs.jpclett.3c00670
Makri is affiliated with the Illinois Quantum Information Science and Technology Center, the Computational Science and Engineering Program, and the Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign.
This work received support from the National Science Foundation.
