Mikael Backlund, assistant professor of chemistry, has received a 2025 National Science Foundation CAREER Award for a research proposal combining theory and experiments to determine the quantum information limits of single-molecule spectroscopy which could lead to advancements in the areas of health, defense, and energy.

Backlund's proposal — "Quantum Information Limits of Single-molecule Microscopy" — combines theory and experiment to determine the speed limits that govern the measurement of molecular processes with light. Light-based chemical measurement and imaging is central to a vast array of technologies that are useful inside the laboratory and outside the lab setting, including technologies in the areas of health, defense, and energy. This work guides the design of optimal measurement schemes, which in turn will enable the development of powerful new devices that might be used, for example, to improve disease diagnoses or detection of chemical weapons, or to enhance the efficiency of solar energy capture.

The Backlund group will theoretically establish and experimentally realize the fundamental precision bounds of single-molecule spectroscopy within the framework of quantum metrology. Their approach probes the limits to single-molecule measurement set by quantum parameter estimation and detection theory. Specific measurement tasks they will address include:

• assessing the limits of spatial resolution of non-photo switching molecules
• discrimination of molecules based on the spectro-temporal properties of emission
• assessing the fundamental limits to single molecule chiroptical discrimination

Backlund said single-molecule microscopy and spectroscopy have been around for a few decades, and these measurements are powerful, because they can reveal information completely hidden by ensemble averaging. But they are also very resource intensive, he said.

"Namely, a molecule will only deliver so many photons before photobleaching, bringing about an abrupt and unwelcome end to the experiment. Because we are so starved for signal-to-noise, single-molecule folks like me often find it useful to formalize the various tasks of our measurements in terms of classical statistical inference theory," he explained. "My group is zooming out one more level to view these problems in the context of quantum statistical inference. Doing so allows us to evaluate and refine our experimental capabilities relative to the fundamental rules of measurement set by quantum mechanics."

In addition to scientific and technological advancements, another goal of the Backlund research group is to broaden participation in, and understanding of, quantum information science (QIS) in disciplines beyond physics and in communities beyond the university. The group will pursue educational initiatives that encourage undergraduate and graduate chemistry students to participate in QIS and broaden participation in QIS through engagement with the local community.

Backlund said Quantum Information Science (QIS) is a hot area of scientific research that will continue to grow into the foreseeable future, and currently, the disciplines of Physics, Electrical Engineering, and Computer Science own a much bigger piece of the QIS pie than does Chemistry.

"One of my goals is to help increase Chemistry's share going forward. In my estimation the biggest barrier to entry is the fact that Chemistry graduates tend to have varying levels of math background. One of the major educational goals of this grant will be to conduct a math bootcamp aimed at incoming Chemistry graduate students and senior undergraduates so that they are better equipped to pursue research in QIS," Backlund explained.