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New quantum sensing method holds promise for improving greenhouse gas detection

Illustration of an optical frequency comb probing gas molecules. Alex Belsley

Press release issued: 4 April 2023

An innovative technique to detect and characterise molecules with greater precision has been proposed, paving the way for significant advances in environmental monitoring, medical diagnostics, and industrial processes.

The new quantum sensing method, put forward by a University of Bristol physicist, builds on the work of 2005 Nobel laureates in physics John Hall and Theodor Hänsch who developed a frequency comb technique to accurately measure optical frequencies. Frequency combs are deployed in many areas of science and industry to characterise matter based on the unique way light is absorbed.

However, the precision of optical comb spectroscopy is limited by a fundamental level of noise present in all lasers and other classical sources of light. A quantum state with reduced noise called ‘squeezed light’ can overcome this limitation and has been harnessed to improve the sensitivity of gravitational wave detectors.

In a paper published in Physical Review Letters, squeezed light is shown to significantly suppress noise over a broad set of comb frequencies used to probe an absorbing molecule.

Author Alex Belsley, Quantum Engineering PhD student, said: “This work proposes a new method for monitoring gas species in situ and with high precision. Quantum advantage in sensing can be realised today and I’m excited for the transformative impact quantum-enhanced sensors will have on our society in the coming years.”

This novel approach could potentially achieve more than a ten-fold improvement in detection limits. In addition to allowing different types of gases to be characterised at ultra-low concentrations, it can also determine important properties such as temperature and pressure with high sensitivity.

Professor Jonathan Matthews, co-director of the Quantum Engineering Technology Labs at the University of Bristol and Alex Belsley’s PhD advisor, said: “Better sensors are important to our future. Healthcare, manufacturing, environmental monitoring and new science itself, all benefit from advances in how we measure physical properties. Alex’s work shows how squeezed light can improve frequency comb spectroscopy – the next step is to explore further with experiments in the lab.”

The research was supported by funding from the UK National Quantum Technologies Programme, the EPSRC Centre for Doctoral Training in Quantum Engineering, and the European Research Council.


‘Quantum-Enhanced Absorption Spectroscopy with Bright Squeezed Frequency Combs’ in Physical Review Letters by Alexandre Belsley

Further information

The Quantum Engineering Technology Labs (QET Labs) has a mission to take quantum science discoveries out of the lab and engineer them into technologies for the benefit of society.  This includes novel routes to quantum computing hardware, quantum communications, enhanced sensing & imaging and new platforms to investigate fundamental quantum physics. QET Labs brings together over £25 million worth of activity and comprises over 100 academics, staff, and students in the Schools of Physics and Electrical and Electronic Engineering at the University of Bristol.

Bristol's EPSRC-funded Quantum Engineering Centre for Doctoral Training offers an exceptional training and development experience for those wishing to pursue a career in the emerging quantum technologies industry or in academia. It supports the understanding of sound fundamental scientific principles and their practical application to real-world challenges.

Quantum information and its translation into technologies is one of the most exciting research activities in science and technology today. Long at the forefront of the growing worldwide activity in this area, the Bristol Quantum Information Institute crystallises our research across the entire spectrum, from theory to technology. With our expert cross-disciplinary team, including founders of the field, we have expertise in all major areas of theoretical quantum information science and in experiment. We foster partnerships with the private sector and provide superb teaching and training for the future generation of quantum scientists and engineers and the prototypes of tomorrow.



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