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• New research proposes a quantum sensing technique that, for the first time, can simultaneously examine multiple parameters of an optical network.
• For the task, researchers from the ����������, England, and the University of Bari, Italy, have developed a new tool.
• Latest development could help advances in a range of fields including medicine and astronomy.

A new method for measuring three different properties of light, at the same time, has been developed using an interferometry-based quantum sensing scheme capable of simultaneously estimating multiple parameters of an optical network.

The approach could help advances in the fields of medicine and astronomy, for example, to improve the precision and scope of quantum measurements across applications ranging from biological imaging to gravitational wave detection.

To date, it has only been possible to measure each parameter individually. However, research  has demonstrated, for the first time, that three independent optical parameters can be measured in a single ‘view' with ultimate quantum precision, without the need to examine each one of them individually.

Researchers from the  in England and  in Italy used available optical resources (such as lasers and squeezed light i.e. quantum light enabling a ‘squeezed noise’, and 'ad hoc’ detection techniques) to create a new instrument – an interferometer. It enables the precise and simultaneous measurement of two unknown phase shifts (small delays or changes in the timing of a light wave as it travels), and an unknown beam splitter reflectivity (the amount of light that is reflected versus how much passes through the beam splitter).

All three parameters could be estimated with a sensitivity which increased, proportionally, the average number of photons employed in the light sources, such as laser light and squeezed light. Such linear scaling in the number of photons is called Heisenberg scaling and is the ultimate scaling in sensitivity which can be achieved in nature thanks to quantum mechanics.

Principal Investigator, Professor Vincenzo Tamma, from the ����������’s Quantum Science and Technology Hub (QSTH), said: “This development can lead to important applications in quantum sensing technologies, based on the use of optical networks. We are currently working on extending our results to the estimation of more than three parameters in more general optical networks.”

This project is supported by   and the  and contributes to the broader work of the ����������’s Quantum Science and Technology Hub (QSTH), which explores how quantum theory can be applied to problems in sensing, imaging, and computation.

The QSTH has worked with several partners worldwide - including numerous academic institutions and industries, such as  and space quantum technology company,  - to achieve a deeper understanding of quantum science, develop novel quantum technologies, and to boost the industrial use of quantum technologies at the crossover between different disciplines.

The research hub has also contributed to the excellent UoP Excellence Framework 2021 results for Physics, ranking Portsmouth as the  across the UK and the top modern university.