At the forefront of optical physics, Professor Vincenzo Tamma, head of the Quantum Science and Technology Hub at the University of Portsmouth, has led a collaborative research effort that redefines what is possible in quantum metrology. Working alongside colleagues from the University of Bari in Italy, Tamma’s team has developed a new quantum sensing method capable of measuring three distinct properties of light simultaneously with the highest precision permitted by nature; the Heisenberg limit.
Rai, A., Triggiani, D., Facchi, P., & Tamma, V. (2025). Simultaneous estimation of three parameters with Heisenberg scaling sensitivity in a two-channel optical network. The European Physical Journal Plus, 140(9), 858. https://doi.org/10.1140/epjp/s13360-025-06805-z
This breakthrough, demonstrates how a two-channel interferometric network can be used to estimate two unknown phase shifts and a beam splitter’s reflectivity all at once. Until now, each of these optical parameters would typically need to be measured separately, requiring multiple experimental setups or sequential procedures. The new approach combines them into a single measurement process that uses quantum states of light to achieve Heisenberg-scaling sensitivity.
Professor Vincenzo Tamma, head of the Quantum Science and Technology Hub at the University of Portsmouth stated,
“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.”
The principle behind this achievement lies in how quantum states of light, such as squeezed vacuum and squeezed-coherent states, interact within an optical interferometer. By exploiting the quantum properties of these states, the team managed to suppress noise below classical limits while enhancing sensitivity across multiple parameters simultaneously. The experiment employs homodyne detection, a well-established optical technique that measures the phase of light waves. When integrated with the quantum-enhanced input states, this method allows for the precise extraction of all three parameters in one run.
According to Professor Tamma, this development could significantly advance quantum sensing technologies that rely on optical networks. These include applications in biological imaging, precision medicine, and astronomical observation—areas where detecting several parameters simultaneously can greatly improve both efficiency and accuracy. The method could also be useful in gravitational wave detection, where the simultaneous monitoring of multiple optical variables plays a crucial role in signal interpretation.
In traditional optical metrology, researchers are often constrained by what is known as the shot-noise limit, where increasing the number of photons only improves measurement precision up to a certain point. However, by using quantum light, specifically squeezed states, this new scheme surpasses that limit. The measurement sensitivity scales with the square of the average photon number, a hallmark of Heisenberg scaling. This means that doubling the photon number leads to a fourfold increase in precision, making the method fundamentally more powerful than classical approaches.
The setup itself is conceptually elegant. Light is injected into an optical network consisting of two input channels, a beam splitter, and phase shifters that introduce small but measurable delays in the light’s path. The quantum states of light are carefully prepared and sent through the network, and the outputs are analyzed using homodyne detection. The data extracted allows for the reconstruction of both the phase delays and the reflectivity, giving a comprehensive snapshot of the optical system’s behavior.
The study is not only a theoretical contribution but also a step toward practical implementation. Since the proposed setup relies on standard optical components such as lasers, beam splitters, and detectors—tools already available in most optical laboratories—it paves the way for immediate experimental validation. The researchers emphasize that their method does not require exotic or difficult-to-produce quantum states, which often limit the feasibility of similar proposals. Instead, it relies on Gaussian states of light, which are more readily generated and controlled.
One of the key achievements of this work is that it does not compromise precision when measuring multiple parameters simultaneously. In most cases, attempting to measure several quantities at once results in trade-offs, where the accuracy of one measurement reduces the precision of another. The new interferometric design avoids this problem by mathematically structuring the system so that the quantum information corresponding to each parameter is extracted efficiently and independently.
Professor Tamma notes that this research could lay the groundwork for future developments in multiparameter quantum metrology. His team is already exploring how the approach can be expanded to measure more than three parameters within more complex optical networks. If successful, this would represent a major step toward building robust quantum sensors capable of performing real-time, high-precision monitoring across diverse environments.
From an engineering standpoint, the implications are substantial. Multi-parameter quantum sensors could transform fields such as navigation, imaging, and environmental monitoring by offering devices that are both highly sensitive and resource-efficient. In quantum communication, such sensors could be used to characterize optical channels more effectively, improving signal reliability and security.
The collaboration between the University of Portsmouth and the University of Bari highlights the importance of international research partnerships in advancing fundamental science. By combining theoretical insights with experimental feasibility, the team has taken a major stride toward integrating quantum-enhanced sensing into practical technology.
In the coming years, as quantum technologies move from theory into applied systems, methods like this will likely become foundational tools for next-generation measurement science. What began as an exploration of the limits of precision has now opened a new chapter in how we observe and understand light itself—a shift that could influence not only physics laboratories but also a wide range of industries that depend on accurate optical measurement.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
