. Scientific Frontline: Researchers create exotic quantum light states

Tuesday, March 21, 2023

Researchers create exotic quantum light states

The graphic symbolizes how photons are coupled after they have been scattered on an artificial atom - a so-called quantum dot - in a cavity resonator.
Illustration Credit: © University of Basel

Coupled light particles could advance both medical imaging and quantum computing.

Light particles, also called photons, do not normally interact with each other. An international research team has now been able to show for the first time that a few photons can be manipulated in a controlled manner and brought into interaction. This opens up new opportunities in the development of quantum technologies. The results are described by a team from the University of Basel, the University of Sydney and the Ruhr University Bochum in the journal Nature Physics, published online on the 20th. March 2023.

Measure distances and transmit information using light

Photons do not interact with each other in a vacuum; they can fly through each other undisturbed. This makes them valuable for data transfer because information can be transported almost trouble-free at the speed of light. Light is helpful not only for data transmission, but also in certain measuring instruments, because it can be used to determine tiny distances, for example in medical imaging. The sensitivity of such measuring instruments depends on the average number of photons in the system.

Even if photons do not interact with each other, they still interact with other materials, for example when they fly through glass. This interaction is usually independent of the intensity of the light. Only when using very high-energy laser light does the intensity influence the interaction. In the current work, the researchers now showed such an intensity effect for only two photons. They demonstrated that a single photon flew through their measuring instrument a little slower than two photons.

The researchers also demonstrated the stimulated light emission postulated by Einstein in 1916 for the first time for individual photons. The effect was the basis for the invention of the laser and has previously only been observed in a large number of photons.

Quantum light generated using artificial atoms

In order to manipulate the light in the manner described, the team created a cavity in a semiconductor that held the light particles, as well as an artificial atom, a so-called quantum point. In this, the photons were connected to each other, and a new entangled state emerged - a kind of community of fate in which the double pack behaves differently than individual photons.

Better resolution and higher sensitivity with quantum light

Such entangled quantum light basically enables more sensitive measurements with higher resolution. Since the technology is based on a few photons, it would also be advantageous for light-sensitive samples, as are often the case in biological microscopy, where the structures to be dissolved are also very small.

The team around Dr. Arne Ludwig from the Ruhr University Bochum. The experiments led the group around Dr. Natasha Tomm and Prof. Dr. Richard Warburton from the University of Basel. Dr. laid the theoretical foundations. Sahand Mahmoodian from the University of Sydney and from Leibniz Universität Hannover.

The researchers hope that their experiments are the first step in making quantum light usable for applications.

Funding: The work was supported by the Swiss National Science Foundation, the European Union as part of the Horizon 2020 program, the Research Fund of the University of Basel, the German Research Foundation, the Federal Ministry of Education and Research as well as the Australian Research Council and ARC Center of Excellence in Engineered Quantum Systems.

Published in journalNature Physics

Additional information: Natasha Tomm, Sahand Mahmoodian, Nadia O. Antoniadis, Rüdiger Schott, Sascha R. Valentin, Andreas D. Wieck, Arne Ludwig, Alisa Javadi, Richard J. Warburton

Source/CreditRuhr University Bochum

Reference Number: qs032123_01

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