Ultimate precision in measuring multiple light parameters with new quantum sensing approach

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 published in The European Physical Journal Plus 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 University of Portsmouth in England and the University of Bari 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 University of Portsmouth’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.”