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Breakthrough paves way for photonic sensing at the ultimate quantum limit

Photonic chip with a microring resonator nanofabricated in a commercial foundry. Photo credit: Joel Tasker, QET Labs

Press release issued: 6 June 2022

A Bristol-led team of physicists has found a way to operate mass manufacturable photonic sensors at the quantum limit. This breakthrough paves the way for practical applications such as monitoring greenhouse gases and cancer detection.

Sensors are a constant feature of our everyday lives. Although they often go unperceived, sensors provide critical information essential to modern healthcare, security, and environmental monitoring. Modern cars alone contain over 100 sensors and this number will only increase. 

Quantum sensing is poised to revolutionise today's sensors, significantly boosting the performance they can achieve. More precise, faster, and reliable measurements of physical quantities can have a transformative effect on every area of science and technology, including our daily lives. 

However, the majority of quantum sensing schemes rely on special entangled or squeezed states of light or matter that are hard to generate and detect. This is a major obstacle to harnessing the full power of quantum-limited sensors and deploying them in real-world scenarios. 

In a paper published in Physical Review Letters, a team of physicists at the Universities of Bristol, Bath and Warwick have shown it is possible to perform high precision measurements of important physical properties without the need for sophisticated quantum states of light and detection schemes. 

The key to this breakthrough is the use of ring resonators – tiny racetrack structures that guide light in a loop and maximize its interaction with the sample under study. Importantly, ring resonators can be mass manufactured using the same processes as the chips in our computers and smartphones. 

Alex Belsley, Quantum Engineering Technology Labs (QET Labs) PhD student and lead author of the work, saidWe are one step closer to all integrated photonic sensors operating at the limits of detection imposed by quantum mechanics. 

Employing this technology to sense absorption or refractive index changes can be used to identify and characterise a wide range of materials and biochemical samples, with topical applications from monitoring greenhouse gases to cancer detection. 

Associate Professor Jonathan Matthews, co-Director of QETLabs and co-author of the work, stated: “We are really excited by the opportunities this result enables: we now know how to use mass manufacturable processes to engineer chip scale photonic sensors that operate at the quantum limit.” 


'Advantage of coherent states in ring resonators over any quantum probe single-pass absorption estimation strategy,' by Alexandre Belsley, Euan J. Allen, Animesh Datta, and Jonathan C. F. Matthews is published in Physical Review Letters. 

Further information

The Quantum Engineering Technology Labs (QET Labs)

QET Labs was launched in 2015, with the 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 £28 million worth of activity and comprises over 100 academics, staff, and students in the Schools of Physics and Electrical and Electronic Engineering. Read more: 

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. 

Bristol Quantum Information Institute

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.  

This research was supported by funds from the UK National Quantum Technologies Programme, the UK Quantum Technology Hub in Quantum Enhanced Imaging QUANTIC, the EPSRC Centre for Doctoral Training in Quantum Engineering, and the European Research Council. All the funding sources are outlined in full in the paper. 

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