Quantum sensing achieves unprecedented precision in light displacement detection

A study led by the University of Portsmouth has achieved unprecedented precision in detecting tiny shifts in light displacements at the nanoscale. This is relevant in the characterization of birefringent materials and in high-precision measurements of rotations.

The quantum sensing breakthrough is published in the journal Physical Review A, and has the potential to revolutionize many aspects of daily life, industry, and science.

Imagine two photons, massless particles of light, that are intertwined in a unique way, meaning their propagation is connected even when they are separated. When these photons pass through a device that splits the particles of light into two paths—known as a beam-splitter—they interfere with each other in special patterns. By analyzing these patterns, researchers have developed a highly precise method to detect even the tiniest initial spatial shifts between them.

The researchers have developed a technique that suggests quantum interference could enable the highest possible precision in detecting such displacements, surpassing traditional measurement techniques.

What makes this proposed method even more remarkable is its ability to maintain accuracy regardless of the size of the displacement, making it highly reliable for tracking changes over time.

The study’s Principal Investigator and co-author Professor Vincenzo Tamma, Director of the University of Portsmouth’s Quantum Science and Technology Hub, said, “This development in quantum sensing represents a significant step towards making high-precision measurement tools more practical and accessible, with far-reaching implications across multiple fields.

“By understanding the quantum nature of the world around us, we can go beyond classical physics and the capabilities of classical devices. This latest study helps us better exploit the quantum laws that govern our universe and, in particular, quantum interference and entanglement to develop quantum technologies.”

The study also found that even simple and inexpensive detectors—known as bucket detectors—can effectively estimate small displacements. This means that high-precision quantum measurements could be achieved without the need for costly, complex equipment, making advanced sensing technology more accessible across various industries.

Professor Tamma explained, “Currently, many quantum sensing technologies are limited to high-end laboratories due to their complexity and cost.

“By developing methods that achieve the ultimate quantum sensitivity with simpler, more affordable equipment, this research brings us closer to integrating quantum sensing into mainstream applications.”

The study, which was included in the journal’s Editors’ Suggestion, promises that the best precision possible in nature can be achieved in the near future in real world scenarios.

“We have shown this technique is feasible and efficient for real-world application,” added Professor Tamma. “Leading experimental groups have already been collaborating with us in putting the quantum sensing techniques developed in our Quantum Science and Technology Hub to the test and making such technologies a reality. I am also looking forward to seeing this more recent sensing scheme experimentally released in the near future.”

Quantum superposition (the ability of a particle to be in a superposition of two states at the same time), entanglement between two particles (the ability to instantaneously change the state of one particle by measuring its entangled counterpart, even at large distances), and quantum interference (in which particles interfere as waves) have puzzled scientists around the world for more than a century, including Einstein.

The Quantum Science and Technology Hub (QSTH) has worked with several partners worldwide—including numerous academic institutions and industries, such as IBM and space-based quantum technology company, Xairos—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 QSTH connects the University’s core quantum science and technology staff with experts in artificial intelligence (AI), biomedical engineering, medicine, computing, environmental science and gravitation—and with external collaborators on four continents.