Quantum-led laser system measures distance with sub-mm accuracy

23 Mar 2026

Method from University of Bristol functions well against strong solar background.

A new laser range-finding technique, inspired by quantum physics, that can measure distances under strong solar background has been demonstrated by researchers at the University of Bristol, UK. The team has proved their hypothesis by testing out their new method on some of the university’s most iconic buildings.

In their study published in Nature Communications, the researchers have shown that ideas originally developed for quantum sensing can be translated into practical laser systems capable of operating in real-world environments.

Disruptive “noise” from sunlight and atmospheric conditions is one of the biggest challenges for long-distance optical sensing. By suppressing this noise while maintaining strong signals, the new technique could enable a wide range of applications such as improving sensing for autonomous vehicles, high-precision surveying and infrastructure monitoring, navigation and positioning systems, and even long-range measurements for space exploration.

To overcome this noise limitation, the team drew inspiration from a quantum effect known as “energy-time entanglement”. Instead of generating quantum light, they recreated its key noise-resistant features using a classical laser system.

Precise – and eye-safe

The system measured the distance on the university's campus between the Queens Building and the Wills Memorial Building with better than 0.1-millimeter accuracy over a distance of about 155 meters, despite changing sunlight and weather conditions. The measurements were made using laser power well below that of a common laser pointer and took only one-tenth of a second.

By shaping and rapidly switching the wavelength of laser pulses using optical fibers and electronic modulators, the researchers produced signals with engineered correlations that behave similarly to quantum ones when rejecting background noise. Crucially, these signals are millions of times brighter than typical quantum light sources.

Lead authors Dr. Weije Nie, Research Fellow and Prof. John Rarity FRS in the School of Electrical, Electronic and Mechanical Engineering at the University of Bristol, explained, “This work addresses a long-standing question in quantum sensing—whether the advantages seen in quantum experiments can be reproduced using more practical technologies.

“Our results show that strong noise reduction does not necessarily require true quantum entanglement. Carefully engineered classical correlations can deliver many of the same practical benefits while remaining scalable and robust.”

The team further validated their approach by performing distance measurements across the campus between the Queens Building and the nearby Cabot Tower at ranges beyond 400 meters. The experiments took place in full daylight and under changing weather conditions, demonstrating that the system can operate reliably outside controlled laboratory settings.

Co-author Dr. Alex Clark, Associate Professor in Quantum Technologies in the School of Physics, added, “The university has a long history of breakthroughs in quantum science and technology, and it was fitting that we were able to test our new technique using some of our most historic buildings. The next steps for this research are to increase the range over which the system can work and to miniaturize the fiber-optic system using integrated photonic devices to ease deployability.”