Twin photons from different quantum dots

Twin photons from uneven sources

Basel researchers have different quantum dots, but they emit exactly the same light particles.Credits: University of Basel, Faculty of Physics

The same light particle (photon) is important for many technologies based on quantum physics. A team of researchers from Basel and Bochum produced the same photon with different quantum dots. This is an important step towards applications such as tap-proof communications and quantum internet.

Many techniques that utilize quantum effects are based on exactly equal photons. However, it is very difficult to generate such photons. Not only do they need to have exactly the same wavelength (color), but their shape and polarization also need to match.

A team of researchers led by Richard Warburton of the University of Basel has worked with colleagues at the University of Bochum to successfully create identical photons originating from different, widely isolated sources.

Single photon from quantum dot

In their experiments, physicists used so-called quantum dots, which are semiconductor structures that are only a few nanometers in size. At quantum dots, electrons are trapped so that they can only take very specific energy levels. When you move from one level to another, light is emitted. Therefore, with the help of a laser pulse that triggers such a transition, a single photon can be generated at the push of a button.

“In recent years, other researchers have already created identical photons with different quantum dots,” explains postdoctoral fellow Lian Zhai, the lead author of a recently published study. Nature nanotechnology.. “But in order to do so, they had to select and select the most similar one from a huge number of photons using an optical filter.” Thus, the available photons. There was very little left.

Warburton and his collaborators have opted for another, more ambitious approach. First, Bochum experts produced the very pure gallium arsenide from which quantum dots are made. Therefore, the natural variation between different quantum dots can be minimized. Basel physicists then used electrodes to expose the two QDs to a precisely tuned electric field. These fields have been adjusted to change the energy level of the quantum dots so that the photons emitted by the quantum dots have exactly the same wavelength.

93% identical

To show that the photons are actually indistinguishable, the researchers sent them into a semi-silver mirror. They have observed that in most cases light particles pass through the mirror as a pair or are reflected as a pair. From that observation, they could conclude that the photons are 93% identical. In other words, the photons formed twins, even though they were “born” completely independently of each other.

In addition, researchers have been able to realize key components of quantum computers, the so-called controlled NOT gates (or CNOT gates). Such gates can be used to implement quantum algorithms that can solve specific problems much faster than traditional computers.

“Currently, the yield of the same photon is still about 1 percent,” admits Ph.D. student Gian Nguyen. He was involved in running the experiment with his colleague Clemens Spindler. “But we already have a pretty good idea, but how can we increase its yield in the future?” This will allow the two-photon method to accommodate potential applications in a variety of quantum technologies. increase.

Researchers develop an ideal single photon source

For more information:
Liang Zhai et al, Quantum Interference of Same Photons from Remote GaAs Quantum Dots, Nature nanotechnology (2022). DOI: 10.1038 / s41565-022-01131-2

Courtesy of University of Basel

Quote: Twin photons from different quantum dots (June 13, 2022) get June 13, 2022 from https: // Did

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