Researchers led by Rice University's Guido Pagano used a specialized quantum device to simulate a vibrating molecule and track how energy moves within it. The work, published Dec. 5 in Nature Communications , could improve understanding of basic mechanisms behind phenomena such as photosynthesis and solar energy conversion.
The researchers modeled a simple two-site molecule with one part supplying energy and the other receiving it, both shaped by vibrations and their environment. By tuning the system, they could directly observe energy moving from donor to acceptor and study how vibrations and energy loss influence that transfer, providing a controlled way to test theories of energy flow in complex materials.
"We can now observe how energy moves in a synthetic molecule while independently adjusting each variable to see what truly matters," said Pagano, assistant professor of physics and astronomy.
A programmable molecule with trapped ions
The experiment used a chain of trapped atoms made from two isotopes of the same element. One isotope encoded the molecular information, while the other formed the environment surrounding the molecule.
Along with two chosen natural vibrations of the trapped ions, this arrangement allowed a representation of a molecule with a donor site and an acceptor site linked to two types of molecular vibrations, a simplified representation of real molecular systems with many energy sites and vibrations.
The research team employed lasers to create and manipulate the energy states and vibrations within the molecule. Moreover, the team introduced a mechanism for the vibrations to lose energy, similar to how real molecules dissipate energy to their surrounding environment.
Earlier experiments either lacked multiple types of vibrations or could not control energy loss from the environment. In contrast, this setup included both, using two types of ions and 12 finely tuned laser frequencies to selectively drive or suppress specific changes in the system.
Once the apparatus was set up, the researchers created an energy surge at the donor site and followed its movement to the acceptor over time.
"By adjusting the interactions between the donor and acceptor, coupling to two types of vibrations and the character of those vibrations, we could see how each factor influenced the flow of energy," Pagano said.
Tracking energy flow under controlled conditions
When the researchers tested their hypothesis, they found that adding more vibrations sped up energy transfer and opened additional pathways for energy to move. In some cases, those pathways reinforced one another, allowing energy to flow more efficiently even as the system lost energy to its surroundings.
They also discovered that when the vibrations differed from one another, energy transfer became less sensitive to mismatches between donor and acceptor energies. This widened the range over which efficient transfer could occur.
"The results show that vibrations and their environment are not simply background noise but can actively steer energy flow in unexpected ways," Pagano said.
Unlike traditional chemical experiments, where multiple factors can be entangled and difficult to separate, the quantum simulator permits independent adjustment of each parameter. This clarity aids in disentangling competing effects and testing foundational concepts in a controlled environment, Pagano said.
Implications for practical devices
These findings could help inform the design of organic solar cells, molecular wires and other devices that depend on efficient energy or charge transfer. By understanding how vibrations influence this flow under various conditions, engineers might develop materials that leverage these quantum effects rather than being hindered by them.
"These are the kinds of phenomena that physical chemists have theorized exist but could not easily isolate experimentally, especially in a programmable manner, until now," said Visal So, a Rice doctoral student and first author of the study.
Co‑authors include Rice's Midhuna Duraisamy Suganthi, Mingjian Zhu, Abhishek Menon, George Tomaras and Roman Zhuravel along with Han Pu , professor of physics and astronomy, Peter Wolynes , the D.R. Bullard-Welch Foundation Professor of Chemistry, and Jose Onuchic , the Harry C. and Olga K. Wiess Chair of Physics.
The Welch Foundation, Office of Naval Research, National Science Foundation CAREER Award, Army Research Office and Department of Energy supported this study.
