Scientists at the University of California, Riverside are making breakthroughs in understanding how quantum wave functions move across ultra-thin materials — research that could eventually improve solar energy technologies and help lay the groundwork for new forms of quantum computing.
The researchers are part of UCR’s Center for Quantum Vibronics in Energy and Time (QuVET), which was established two years ago and focuses on “vibronics,” the interaction between vibrations and electronic quantum states. The center examines both biological molecules and synthetic layered materials, where the same fundamental quantum processes emerge across vastly different systems. Its research brings together physicists, chemists, engineers, and biochemists from multiple institutions to better understand how vibrations shape quantum behavior.
Quantum mechanics is the branch of physics that describes how matter and energy behave at extremely small scales, such as atoms and electrons. A quantum wave function is the mathematical description of a particle’s possible states and locations — effectively describing the probability of where an electron might exist and how it behaves.
QuVET researchers recently published three papers exploring how quantum wave functions behave in atomically thin layered materials. The papers — all of which received special designation as Editors’ Suggestions — introduce new materials, device architectures, and measurement techniques that will allow QuVET researchers to probe those effects more deeply.
In one study published in Physical Review Letters, researchers showed that applying an electric field to a two-layer ultrathin device allowed them to precisely control where a positively charged quantum wave function resided.
“The wave function could be shifted into the first layer, the second layer, or exist in both layers simultaneously — a phenomenon known as quantum superposition,” said Nathaniel Gabor, a professor of physics and astronomy and the study’s senior author. “We found that this quantum ‘balancing act’ directly altered the optical properties of the material.”
The other two papers, co-authored by Gabor and led by his QuVET colleagues Xiaoyang Zhu and Eric Arsenault at Columbia University, explore related quantum behaviors in layered materials. They establish new ways to manipulate quantum states in materials only a few atoms thick, opening new possibilities for energy conversion and future quantum technologies.
“One of the important things we know from biology is that the electron wave function moves in unusual ways,” said Gabor, who serves as QuVET’s director. “That movement is what allows photosynthesis to work.”
Gabor explained that in photosynthesis, light creates a charge-neutral quantum excitation that moves from molecule to molecule in plant leaves until it reaches a reaction center, where it separates into an electron and a positive charge. That separation allows living systems to harvest energy from sunlight.
QuVET is studying how similar processes occur in atomically thin materials built in the lab. Center researchers are also manipulating how quantum mechanics allows wave functions to exist in multiple places simultaneously.
“In these layered materials, we can think about how a quantum wave function on one layer hops to another layer, and by using voltages and currents, we can experimentally control those transitions,” Gabor said. “We can even place the wave function on one layer or the other or distribute it across both at the same time — something that 20 years ago would have sounded impossible, but now it’s experimentally controllable.”
QuVET researchers want to be able to decide whether a wave function jumps across an interface or stays where it is.
“The idea is that vibrations may become the control knob, enabling future ‘quantum vibronic switches’ that use crystal vibrations to turn quantum transitions on and off,” Gabor said.
Understanding that process is essential for improving energy conversion technologies, including solar power generation. When light strikes a material, it creates a neutral excitation that must be separated into free charges before usable electricity can be produced.
“If you don’t get the energy out fast enough, it can be lost as heat or re-emitted as light,” Gabor said. “Biology has evolved systems that pull the energy out extremely quickly, and we’re trying to understand how to do the same thing in synthetic materials.”
To study these ultrafast processes, QuVET researchers use spectroscopy techniques that observe events on femtosecond and picosecond timescales — trillionths and quadrillionths of a second.
The implications may extend far beyond energy harvesting. The researchers believe the same physics could eventually enable new forms of quantum control and computation.
“We know vibrations can dramatically affect the efficiency of these systems,” Gabor said. “What we still need is a deeper understanding of why — and given how quickly the field is advancing, we’re likely to have answers soon. At the frontier of experimental science, we’re now routinely controlling quantum wave functions at incredibly small scales. That still amazes me.”
Tania Paskova, U.S. Army Combat Capabilities Development Command Army Research Office program manager, noted that scientists often look to nature to understand the mechanisms at work and to explore their translation into artificial systems.
“This research is answering critical scientific questions that could become instrumental in understanding and controlling vibronic effects in artificial biological systems,” she said. “By establishing roadmaps for using vibronic effects for novel quantum photonic and optoelectronic devices, this research has the potential to significantly advance future Army capabilities in quantum computing, secure communications, and sensing technologies.”
This research was supported by the Development Command Army Research Office through a Multidisciplinary University Research Initiative grant.
