Team controls two quantum light sources

Illustration of chip comprising two entangled quantum light sources. (Credit: NBI)

Researchers report the ability to control two quantum light sources rather than one.

For years, researchers around the world have strived to develop stable quantum light sources and achieve the phenomenon known as quantum mechanical entanglement—a phenomenon, with nearly sci-fi-like properties, where two light sources can affect each other instantly and potentially across large geographic distances. Entanglement is the very basis of quantum networks and central to the development of an efficient quantum computer.

Researchers from the University of Copenhagen’s Niels Bohr Institute report the feat in the journal Science. According to professor Peter Lodahl, it is a crucial step in the effort to take the development of quantum technology to the next level and to “quantize” computers, encryption, and the internet.

“We can now control two quantum light sources and connect them to each other. It might not sound like much, but it’s a major advancement and builds upon the past 20 years of work. By doing so, we’ve revealed the key to scaling up the technology, which is crucial for the most ground-breaking of quantum hardware applications,” says Lodahl.

The magic all happens in a so-called nanochip not much larger than the diameter of a human hair.

Lodahl’s group has only been able to control one light source until now because light sources are extraordinarily sensitive to outside “noise,” making them very difficult to copy. In their new result, the research group succeeded in creating two identical quantum light sources rather than just one.

“Entanglement means that by controlling one light source, you immediately affect the other. This makes it possible to create a whole network of entangled quantum light sources, all of which interact with one another, and which you can get to perform quantum bit operations in the same way as bits in a regular computer, only much more powerfully,” explains postdoc Alexey Tiranov, the article’s lead author.

This is because a quantum bit can be both a 1 and 0 at the same time, which results in processing power that is unattainable using today’s computer technology. According to Lodahl, just 100 photons emitted from a single quantum light source will contain more information than the world’s largest supercomputer can process.

By using 20-30 entangled quantum light sources, there is the potential to build a universal error-corrected quantum computer—the ultimate “holy grail” for quantum technology, that large IT companies are now pumping many billions into.

With the new research breakthrough, the fundamental quantum physics research is now in place. Now it’s time for others to take the researchers’ work and use it in their quests to deploy quantum physics in a range of technologies.

“It is too expensive for a university to build a setup where we control 15-20 quantum light sources. So, now that we have contributed to understanding the fundamental quantum physics and taken the first step along the way, scaling up further is very much a technological task,” says Lodahl.

The research took place at the Danish National Research Foundation’s “Center of Excellence for Hybrid Quantum Networks (Hy-Q)” and is a collaboration with the Ruhr University Bochum in Germany.

Source: University of Copenhagen