Researchers at South Ural State University (SUSU) have made a significant advance in quantum metrology. A team led by Anna Paterova, Senior Research Fellow at the Quantum Light Engineering Laboratory and recipient of a Mega-Grant for Young Scientists in "IR Metrology Based on Quantum Interferometry," is developing and refining a nonlinear interferometry method that dramatically improves the signal-to-noise ratio in infrared (IR) measurements – turning quantum noise from an obstacle into a useful tool.
The Quantum Light Engineering Laboratory is headed by Dr. Sergei Kulik, Professor at Lomonosov Moscow State University, with Dr. Anna Paterova serving as Senior Research Fellow. Their work under the V.B. Khristenko Grant Programme is one of the laboratory's key research directions.
The main challenge in classical IR spectroscopy is that detectors for this range perform poorly. Thermal noise from objects and even the experimenter's movements can overwhelm weak useful signals.
"In quantum optics, our main enemies are not darkness, but movement, noise, and stray light," explains Anna Paterova. "To minimise these, all experiments are conducted under special conditions: windowless labs to block external noise, cooled detectors, vibration-damping optical tables, and even specific dress codes – light-coloured clothing can reflect light from laptop screens and distort data. When assembling a nonlinear interferometer, stabilisation is critical."
The key breakthrough came from using spontaneous parametric down-conversion (SPDC)- a quantum process resulting from the interaction of laser radiation with electromagnetic vacuum fluctuations. Paradoxically, these inevitable quantum fluctuations – usually associated with noise – actually assist the experiment by triggering the generation of correlated photon pairs.
Inside a nonlinear crystal, the laser generates pairs of correlated photons: one at a visible wavelength and the other in the infrared. The probability of such an event is extremely low (about 10⁻⁶), but it opens up entirely new possibilities. The more powerful the laser, the more precise the measurement.
"We propose a nonlinear interferometry method that enables measurements in the infrared range while detecting visible light," comments Anna Paterova. "Our experiment is called 'Nonlinear Interferometry for Infrared Imaging or Infrared Spectroscopy Applications.
We replace inefficient infrared detectors with visible-range detectors that are immune to thermal noise. Thanks to quantum correlation between photons, by measuring the visible photon's wavelength, we can infer what happened to its IR counterpart. This significantly improves the signal-to-noise ratio compared to classical analogues.
This approach could outperform classical metrology methods, paving the way for more informative measurements, particularly in biomedicine. The technique enables non-invasive analysis of biological tissues by studying characteristic absorption lines of proteins, fats, DNA, and RNA in the infrared range. In the future, this could allow detection of tissue changes at the earliest stages – for example, during drug exposure or pathology development – providing a deeper level of analysis than conventional methods.
The project's work is supported not only by experimental results but also by active personnel training. Research outcomes have been published in leading international journals, including Advanced Photonics Research and Laser Physics Letters.
Recent publications include E.S. Zatsepin et al., "Dispersion Analysis of Silver Thiogallate in a Broad Mid-Infrared Range," Advanced Photonics Research 7(1), e202500267 (2026), which has garnered significant attention, and E.S. Zatsepin et al., "Generation of Spontaneous Parametric Down Conversion from BaGa₂GeS₆ Crystal," Laser Physics Letters 23(1), 015201 (2026).
Within the V.B. Khristenko grant framework, students and postgraduates involved in the project regularly present their findings at conferences. In March 2026, three young researchers – Evgeny Zatsepin (postgraduate), Artem Sabanin (2nd-year Master's student, Department of Nanoelectronics), and Tikhon Leonovets (3rd-year Bachelor's student, Department of Nanoelectronics) – became laureates of the Interuniversity Quantum Network (MUQS) grant competition and successfully defended their work at the IX International School on Quantum Technologies in Sochi. In July 2026, another group of students – Sofia Orlova (4th-year Bachelor's student, Department of Nanoelectronics) and Andrey Shishkin (2nd-year Bachelor's student, Department of Optoinformatics) – will undertake an internship at the Kurchatov Institute in Moscow.
Looking ahead, the next major scientific event will be the VI Scientific and Practical Seminar "Modern Problems of Quantum Technologies: Applied Sensing," to be held at SUSU in late June 2026, bringing together experts in quantum sensing and related fields.
The project is implemented under the V.B. Khristenko Grant Programme "Step into the Future." This programme provides annual financial support for the University's development strategy under the national "Priority-2030" initiative. Grants are awarded for cutting-edge research, talent pipeline development, and the implementation of unique educational programmes that define the development trajectory of SUSU and the Chelyabinsk Region.