Physicists have built a device that allows them to measure the movement of single photons and could lead to advances in medical imaging and quantum computing.

March 21, 2023

Scientists are a step closer to harnessing quantum light energy to turbo charge medical imaging and bolster the power of supercomputers.

An international team of physicists, including Australians, have for the first time identified small numbers of photons – packets of light energy – interacting.

“This fundamental science opens the pathway for advances in quantum-enhanced measurement techniques and photonic quantum computing,” University of Sydney quantum optics expert Sahand Mahmoodian said.

The research team built a hyper-sensitive light-measuring device that allowed them to observe a single photon as it scattered off a quantum dot, which is a type of artificially created atom.

“By demonstrating that we can identify and manipulate photon-bound states, we have taken a vital first step towards harnessing quantum light for practical use,” Dr Mahmoodian said.

University of Basel physicist Natasha Tomm said the delay between photons moving was also recorded.

“With this really strong photon-photon interaction, the two photons become entangled in the form of what is called a two-photon bound state,” she said.

“This is very promising for applications in a wide range of areas from biology to advanced manufacturing and quantum information processing.”

Quantum light could, in principle, make more sensitive measurements with better resolution using fewer photons.

This can be important for applications in biological microscopy when large light intensities can damage samples and where the features to be observed are particularly small.

It builds on the research that led to the invention of the laser, optic fibre and modern medical imaging.

One advantage of using light in communication – through optic fibres – is that packets of light energy, photons, do not easily interact with each other. This creates near distortion-free transfer of information at light speed.

The research was a collaboration between the University of Basel, Leibniz University Hannover, the University of Sydney and Ruhr University Bochum and was published in the journal Nature Physics.