Slovenian lab working with Google on more stable quantum chip technology

This year marks a century since the first laws of quantum mechanics, which is why the United Nations called this the International Year of Quantum Science and Technology. World Quantum Day will be celebrated on 14 April with the aim of fostering understanding of quantum science among the general public.

Quantum science is a standout field of scientific research in Slovenia and the Nanocenter, led by Dragan Mihailović, is working closely with the Google Quantum AI Lab to develop new types of quantum bits or qubits and to find materials for more stable quantum chips, the basic building blocks of future quantum computers.

Current processors, including those in smartphones, use classic bits that can be either in a 0 or 1 state. They are used to perform calculations in a sequence, one bit after another.

Quantum computers use qubits that can exist in multiple states at the same time and are quantum entangled with one another.

"Instead of a sequential processing, they allow for parallel processing of an enormous amount of data and solving extremely complex tasks that traditional computers cannot perform or would need too much time for," Mihailović said.

Sensitivity of qubits to environmental influences a challenge

The sensitivity of qubits poses a significant challenge in the development of quantum computers, Nanocenter post-doctoral researcher Anže Mraz said.

The smallest external influence can break the qubit's state and the precision of the calculation. "In the lab we are focusing on the stability of qubits or their coherence - their ability to maintain a quantum state through a longer time period," he said.

They are currently working with a compound called tantalum disulphide. "This material has long been interesting for basic research. Its advantage is that it can be applied in very thin layers, which is crucial for the production of quantum chips," Mihailović said.

Their lab was among the first in the world to develop thin layers of tantalum disulphide. "The material has a rare quality. It allows us to affect the electrons with an external electric impulse and create new electron states in the material, read them and delete them, which is one of the key steps towards applied quantum electronics," he said, adding that the process can be imagined as putting together a mosaic.

The processes currently in use for quantum chip production are still quite traditional and date back to when stability was not considered as a critical property, so there is still a lot of room for improvement, Mihailović said.

In December 2024 Google presented its new quantum chip Willow. With a special design of connections between the qubits and the use of an algorithm to correct mistakes they were able to maintain the quantum information for a significantly longer time than before. This is an important step in quantum chip stability and thus usability of quantum computers.

Quantum computers are already capable of surpassing traditional computers in some specific tasks but they do not have a direct application value, Mihailović said. Still, the progress shows a broad spectrum of possibilities in the future.

The most promising applications are in the pharmaceutical industry. Quantum computers could significantly speed up the development of new medicine and make it more affordable. In the future they could also improve transport and logistics systems, make communications more secure, develop better batteries, search for new materials and do tasks that cannot be imagined now.

Strong ties at home and abroad needed for breakthroughs in the quantum world

The cooperation of Slovenian researchers with Google's researchers is very dynamic. "Even though we are far apart physically, the communication is fluid and frequent," Mihailović said. The results of their work are published in prestigious scientific journals, "so we have a feeling that we are constantly in contact with a large, internationally connected research environment, which is especially important for young researchers," he said.

"It is important to be involved in an environment where something is happening constantly and we have insight into the latest challenges and directions in quantum science."

While the lab is already working with several Slovenian companies to develop machinery to produce prototypes of chips, Mihailović believes there are many more opportunities for cooperation. "It often happens that someone is already developing something very useful and we simply don't know about it. Slovenia's research and industry are still not connected enough," he said.

Nanocenter is in the process of joining Central European Research Infrastructure Consortium (CERIC), a consortium that brings together research infrastructure around Europe and provides access to research equipment and expertise in materials and nanotechnology to researchers around Europe and elsewhere.

"We are the only infrastructure centre in Slovenia that already allows open access to top research equipment to external users. Joining CERIC will open doors for Slovenia to new partnerships, opportunities for international cooperation and scientific progress," Mihailović said.