Reviewed by Louis CastelFeb 5 2025
According to a study published in Science Advances, an international collaboration of engineers and physicists has developed a method to enhance the capabilities of advanced spectroscopy using quantum light. This innovative approach allows for infrared electric field measurements that are twice as sensitive compared to earlier techniques in time-domain spectroscopy.
Image Credit: University of Glasgow
The findings could pave the way for new applications in security and medical diagnostics.
Time-domain spectroscopy currently employs ultra-short laser light pulses that interact with material samples, enabling detailed analysis of their molecular composition over time—something other spectroscopy methods cannot achieve.
Recent work by the 2023 Nobel Prize laureate Ferenc Krausz's team indicated that this technique could identify early disease markers, such as cancer, in blood samples.
However, the use of classical light sources in time-domain spectroscopy has constrained its resolution due to a phenomenon known as 'shot noise.' This limitation means that, after a certain threshold, the noise obscures the signal, preventing further insights into the material's composition.
The new technique leverages quantum light to surpass the constraints of classical light.
The researchers utilized pairs of laser pulses that are entangled through quantum mechanics to investigate an infrared field.
Both beams experience shot noise and the content of the noise is identical in both. By subtracting the measurements from one beam from the other, signals that would typically be masked by shot noise in classical light can be detected, resulting in more sensitive measurements. The team reports that their method is approximately half as noisy as classical time-domain spectroscopy, effectively doubling its sensitivity.
Although the technology is still developing, in the future time-domain spectroscopy could help us better understand what materials are made of, detect contaminants or traces of dangerous material like explosives in the atmosphere, or probe the concentration of molecules of serious diseases in patients’ blood samples. We have been working for several years now to apply quantum measurement techniques to time-domain spectroscopy, and this paper demonstrates the effectiveness of quantum radiation for increasing the sensitivity of the technique.
Matteo Clerici, Study Corresponding Author and Professor, James Watt School of Engineering, University of Glasgow
He added, “Glasgow PhD students Dionysis Adamou and Lennart Hirsch worked hard to make this happen, and the next steps for us are to look at ways to enhance the technique beyond what we’ve been able to achieve so far. That will likely involve adapting interferometry techniques like those used in gravitational wave detectors to improve the sensitivity of the process.”
Researchers from Loughborough University and the University of Strathclyde also played a role in developing this new technique.
Funding from Innovate UK; UK Research and Innovation (UKRI); the Engineering and Physical Sciences Research Council (EPSRC); the University of Glasgow Impact Acceleration Account; the Defence Science and Technology Laboratory (DStl); the Royal Academy of Engineering; the Leverhulme Trust; the devcOM US Army Research Office and the European Commission supported the study.
Journal Reference:
Adamou, D., et. al. (2025) Quantum-enhanced time-domain spectroscopy. Science Advances. doi.org/10.1126/sciadv.adt2187