Quantum optics may turn this rare visual phenomenon into an eye test
Engineered light transforms Boehm’s brushes from a faint visual pattern into a much brighter one that could help catch retinal disease
University at Buffalo
image:
Illustration of the enhanced Boehm's brush patterns observed during a University at Buffalo-led study. Researchers used a quantum optics technique to make the normally faint visual phenomenon easier to see.
view moreCredit: Dusan Sarenac/University at Buffalo
BUFFALO, N.Y. — Modern life depends on quantum physics. It makes technologies such as GPS navigation, MRI scanners and computer chips possible.
Now, the same science may also lead to a new way to test the health of our eyes.
A University at Buffalo-led team has used a technique from quantum optics to make a little-known visual pattern produced inside the eye easier to see — potentially opening the door to a new way to test retinal health.
Known as Boehm’s brushes, these faint, two-lobed, bowtie-shaped patterns sometimes appear in peripheral vision when polarized light scatters off structures in the retina. Because people with retinal disease may be less likely to perceive them, scientists have long wondered whether they could serve as a biomarker of retinal health.
However, Boehm’s brushes are often too hard to see, even for people with healthy eyes, to be useful in clinical practice.
In a study published today (July 9) in the Proceedings of the National Academy of Sciences (PNAS), researchers used a specially engineered form of polarized light to enhance the perception of Boehm's brushes in about a dozen healthy volunteers.
“Our structured light transformed the normally faint, two-lobed bowtie patterns into brighter, easier-to-see ones with a variable number of lobes,” says corresponding author Dusan Sarenac, PhD, assistant professor of physics in the UB College of Arts and Sciences. “The more complex patterns give us multiple ways to measure patients’ perception of the phenomenon and, potentially, the health of their retinas.”
The researchers used what's known as structured light, an engineered form of polarized light developed for quantum optics and used in microscopy and precision sensing. Unlike ordinary polarized light, its carefully arranged polarization pattern better matches the symmetry of structures in the retina.
When the structured light reached the retina, Boehm's brushes appear larger, brighter and more complex.
The experiments were done at the School of Optometry at the University of Waterloo. The participants viewed the structured light through an optical setup similar to a traditional eye exam and answered questions about what they saw. After each response, the system automatically adjusted the contrast, making the pattern easier or harder to see until it determined each participant's visual threshold.
“Instead of simply asking participants whether they saw Boehm’s brushes, we measured how many lobes they saw, the contrast they needed to detect them and where the patterns appeared in their visual field,” says first author Dmirtry Pushin, PhD, associate professor of physics at the University of Waterloo.
The researchers found that participants with healthy eyes detected the patterns more easily farther from the center of vision — an expected result that provides a baseline for future studies.
The next step, Sarenac says, is to test people with retinal diseases, such as macular degeneration. The goal would be to determine whether damaged areas of the retina change how they perceive the patterns.
The study was conducted in collaboration with the Centre for Eye and Vision Research (CEVR), a Hong Kong-based institute founded by Hong Kong Polytechnic University and the University of Waterloo. Before joining UB, Sarenac was a co-principal investigator at CEVR and a senior technical lead of transformative quantum technologies at the University of Waterloo’s Institute for Quantum Computing.
This work was supported by the Natural Sciences and Engineering Research Council of Canada and the Canada First Research Excellence Fund.
Journal
Proceedings of the National Academy of Sciences
Method of Research
Experimental study
Subject of Research
People
Article Title
Topological expansion of Boehm’s brushes via structured light
Article Publication Date
9-Jul-2026
Quantum material opens new path for studying unusual electronic behavior
Penn State
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A research team has developed a quantum material that could power devices capable of untraditional transport and grouping of electrical signals and quantum states, testing the material in an experimental device to measure how electricity moves through the material.
view moreCredit: Jaydyn Isiminger / Penn State
UNIVERSITY PARK, Pa. — By combining approaches from two rapidly growing fields of quantum physics, researchers at Penn State and Saint Louis University have demonstrated a novel specialized material can naturally enable a new way to study unusual physical phenomena known as non-Hermitian dynamics.
The work lays the foundation to build a new platform to explore phenomena that could power devices capable of transporting and grouping electrical signals and quantum states in ways not traditionally achievable without relying on optic or engineered systems. The team detailed their findings in a paper published in Science Advances.
Non-Hermitian physics refers to systems that exhibit behaviors not found in conventional physical models, explained Morteza Kayyalha, assistant professor of electrical engineering at Penn State and corresponding author on the paper. These systems can display unusual behaviors, such as enhanced responses to perturbations and external stimulus. They can also demonstrate the non-Hermitian skin effect, where quantum states — which researchers can use to predict the physical properties of a material — become concentrated near a specific boundary or point in the material, rather than spreading uniformly throughout.
Kayyalha and his collaborators’ work focuses on the development of a magnetic topological insulator, otherwise known as a quantum anomalous Hall (QAH) insulator, which can achieve this behavior. The interior of this material is insulating, stopping the flow of electricity, with electrical current instead passing along the material's edge in a single direction. These one-way edge paths, called chiral edge channels, offer a natural way to build an electronic network whose effective connections are direction dependent, Kayyalha said.
Ordinary electronic networks showcase reciprocal responses between two points, meaning the connection from one point in the system to another is balanced by the connection in the reverse direction, like a two-way highway into a city where cars can enter, but only if the same number of cars leaves. Non-reciprocal systems relax this symmetry — their effective connections can depend on direction, allowing states or electrical signals to accumulate in ways that would not occur in a conventional reciprocal system.
“We wanted to show that these phenomena can emerge naturally in a quantum material,” Kayyalha said. “Our work lays the groundwork for achieving scalable, non-Hermitian behavior with a quantum material platform rather than relying only on optical or circuit-based designs.”
The QAH devices used in the study were made from thin films of the topological insulator bismuth antimony telluride, synthesized in the two-dimensional crystal consortium (2DCC), a facility at Penn State funded by the U.S. National Science Foundation (NSF). The insulator is magnetically doped, a process that introduces magnetic atoms to a non-magnetic base material, creating a quantum state in which current travels along the device boundary through a chiral edge channel. According to Kayyalha, the QAH insulators do not require external magnetic fields, which are usually necessary to achieve non-Hermitian behavior in quantum Hall devices during operation.
“A key advantage of this QAH platform is that, after the material is magnetized, the chiral edge state can be studied at zero applied magnetic field,” Kayyalha said. “That makes it a promising platform for exploring non-Hermitian physics in electronic quantum materials.”
The team built ring-shaped devices from the QAH insulator, connecting multiple electrical contacts around the perimeter of each ring. By carefully measuring how electrical signals traveled between the contacts in one of the rings, the team reconstructed the system’s conductance network, a collection of measurements that visualize how electricity moves through a material. They then compared these measurements to theoretical models, specifically the Hatano-Nelson model, which is a standard model used to identify non-Hermitian behavior in systems.
“We can compare the measured conductance matrix directly with theoretical models of non-Hermitian physics,” Kayyalha said. “From there, we can identify signatures of non-Hermitian dynamics in the quantum material.”
The measurements showed that, in the QAH system, the chiral edge channel realizes a conductance matrix closely related to the Hatano-Nelson model. Furthermore, tuning the device boundary conditions allowed the team to observe the non-Hermitian skin effect, where the system's eigenstates, quantum states that can inform predictions of how a material will behave, become concentrated near one end of the effective chain rather than spreading uniformly.
“The non-Hermitian skin effect has been observed in several engineered platforms but realizing it in a topological quantum material provides a new route for studying these phenomena using electronic transport,” Kayyalha said.
The researchers also noted that the behavior of the system can be tuned by adjusting the gate voltage, an electrical signal that can power or dampen a stronger current, similar to a transistor in commercial electronics. Kayyalha said he believes this will allow researchers to more effectively explore how a material’s conductance impacts its non-Hermitian dynamics.
Beyond demonstrating a new experimental platform, Kayyalha said the work highlights an emerging connection between topological quantum materials and non-Hermitian physics. Although the two fields have largely developed independently, their combination could be key to developing sensors capable of unprecedented responsiveness to electric and magnetic signals, among a host of other stimuli.
“Magnetic topological insulators provide a versatile platform for exploring fundamental questions about non-Hermitian systems, topology and quantum transport,” Kayyalha said. “We know this technique is commercially scalable, but now we need to first demonstrate a use case and see what different types of sensing applications they could be used in.”
Additional Penn State-affiliated co-authors include Nitin Samarth, Verne M. Willaman professor of physics and of materials science and engineering, and associate director of the 2DCC; Le Yi, a physics doctoral candidate; Asmaul Smitha Rashid who received her doctorate in electrical engineering from Penn State; and Emma Steinebronn who received her doctorate in physics from Penn State. Other co-authors include Şahin K. Özdemir and Ramy El-Ganainy, both professors of electrical and computer engineering at Saint Louis University.
This research was supported by the Office of Naval Research, the U.S. National Science Foundation and the Air Force Office of Scientific Research.
Journal
Science Advances
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Non-Hermitian dynamics in quantum anomalous Hall insulators
The ring-shaped devices, magnified on the computer screen in this image, allow researchers to measure how electricity flows between the symmetrical contacts and visualize if there is a buildup of quantum states across the contacts, behavior indicative of the non-Hermitian skin effect. Although the team built multiple rings, they used only one to develop their conductance matrix.
Credit
Jaydyn Isiminger / Penn State
