UC Berkeley researchers use quantum light spectroscopy to better understand photosynthesis

Photo of green leaves of plant
Antonio Martin/Staff
Researchers at UC Berkeley are working to use quantum light spectroscopy to examine entangled photons to answer questions about how light is absorbed during the process of photosynthesis. The research team hopes to use this understanding to further progress in food and energy sectors.

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Researchers at UC Berkeley are using a technique called quantum light spectroscopy to help them better understand the process of photosynthesis.

Kaydren Orcutt, a campus graduate student on the team, said although scientists understand the general process of photosynthesis, they are working on finding out how, exactly, sunlight is absorbed into a plant. The project is a collaborative effort between campus College of Chemistry professor Graham Fleming’s lab and College of Chemistry professor Katharine Birgitta Whaley’s theory group.

“At the cellular level, plant biologists like myself have been able to tease apart the important puzzle pieces, the proteins and pigments, needed to accomplish this feat,” said Dhruv Patel, campus graduate student in the department of plant and microbial biology, in an email. “But we’ve learned that knowledge isn’t enough to mimic that process on our own.”

According to Orcutt, plants are “ridiculously good” at the process of photosynthesis, but humans have not been able to reach the same kind of efficiency in using light.

The team is currently examining photons, which are the smallest particles of light, to look at the smallest scale possible. According to Orcutt, the researchers send a short laser pulse into a special crystal in an attempt to split photons, a rare event that creates an “entangled” pair.

Fleming said the entanglement is what helps them identify photons, and when the researchers identify one photon in a pair, they know there is another somewhere else.

“When they’re entangled and you do something to one, it affects the other one, which is very strange because it doesn’t matter how far apart they are,” Fleming said.

Orcutt said the ultimate goal of the research is to find concrete proof of how individual photons are absorbed in photosynthesis.

“We’re under the assumption it’s going to work this way, and we think we’re going to see that,” Orcutt said. “If we don’t see that, that would be its own massive discovery.”

Fleming said the research could improve crop yields. Past research from Fleming’s lab found that a plant can become damaged if it absorbs too much sunlight, so it regulates the amount it receives. Orcutt added that plants also overregulate, so the team can find the minimum amount of sunlight a plant can absorb for photosynthesis to potentially see how less energy can be wasted.

According to Krishna Niyogi, campus plant and microbial biology professor, although it is too early to tell if the research could have an impact on crops, he would not rule out the possibility. Niyogi’s lab has been collaborating with Fleming’s to understand the regulation of light harvesting in photosynthesis.

COVID-19 has made the research more difficult. According to Fleming, only one-third of his students can be inside the lab at the same time. Orcutt said campus graduate student Quanwei Li has played an important role in the experiment, but they cannot be in the same room together.

Fleming added that the smoke in Berkeley has impacted research progress, as the lasers are shut down when smoke levels are high because burning smoke particles can damage the optics.

Despite this, those in the plant biology field find this project important in understanding the workings of photosynthesis. Niyogi said in an email that the research is “at the cutting-edge frontier of spectroscopy,” and Patel shared similar sentiments.

“Better understanding the biophysics behind photosynthesis, and more importantly how plants do it so well, is an important piece in designing machines that turn sunlight into electrochemical energy of our own,” Patel said in the email.

Contact Natalie Lu at [email protected] and follow her on Twitter at @natalie_c_lu.