Seamless assembly of 2D clusters with more than 100 single-atom quantum systems

Researchers at the Technical University of Darmstadt have recently demonstrated the flawless assembly of versatile target models comprising up to 111 single-atom quantum systems. Their findings, described in an article published in Letters of physical examination, could lead atomic architectures assembled beyond the threshold of quantum advantage, paving the way for new breakthroughs in the field of quantum science and technology.

"Our research is motivated by the realization that the physical sciences are in the midst of a paradigm shift in which the application of quantum physics, that is quantum technologies, is becoming advanced technology in the near future, "said Gerhard Birkl, one of the researchers. who conducted the study, told Phys.org. "A vast list of apps is already predictable, but I'm confident we're not even aware of most apps."

The next step in the field of quantum science and technology is to develop experimental platforms with extensive extensibility, multisite quantum correlations, and efficient quantum error correction. In the last century or so, researchers have done a great deal of work on unique quantum systems, laying the groundwork for current developments. Atomic quantum systems have played a key role in these studies, particularly neutrals trapped by light, as they provide well – isolated quantum systems with favorable scaling.

"For future generations of quantum technologies, switching to multiple quantum systems, that is, increasing the size of the system is essential," Birkl said. "For this reason, we have set ourselves the direction of developing a new platform providing highly scalable architectures for atomic quantum systems, with full control over all relevant parameters to advance advanced quantum technologies."

In developing the technological bases for their experience, Birkl and his students in the study focused on laser-cooled neutral atoms in optical traps, as they benefit from the scientific advances of the last 25 years. These advances include laser cooling and trapping, Bose-Einstein condensation, handling of individual quantum systems and optical tweezers.

"Finally, we have realized that the combination of these scientific developments with advanced optical technologies such as large-scale microlensing network microfabrication generates an ideal platform for the development of scalable quantum technologies," said Birkl. "At the heart of our work, we apply a new experimental architecture in which we generate a 2D pattern of optical traps for neutral atoms based on 2D matrices of microlenses."

Using a large laser beam illuminating many lenses, the researchers were able to generate several laser traps simultaneously. They generated up to 400 of these traps in parallel and were then able to solve them individually.

Their experience has had several stages. Birkl and his colleagues began by creating a cloud of rubidium atoms in a vacuum system at room temperature, using a magneto-optical trap (MOT). This allowed them to generate several million rubidium atoms at a temperature of about 100 microKelvin. Subsequently, they activated the model of laser traps and transferred atoms into these traps, with a maximum of 1 atom per trap.

"We generated models with trapping sites with exactly one or zero atoms," said Birkl. "Then we took a picture of the pattern and this allowed us to identify busy sites (which did not require any additional action) and empty sites."

Once they determined which sites were occupied and which ones were vacant, the researchers filled in all the empty sites; recover a single atom from a filled site outside the target pattern and transport it to an empty site in the target pattern. This transport process was performed with the aid of a single-focus laser beam that can move in 2D throughout the trap network.

"It works like a tweezers made in the light.This is why they are called" optical tweezers. "It's the invention of Dr. Arthur Ashkin, who received a part Nobel Prize in Physics 2018 for this invention, "said Birkl. "After applying the tweezers to all the empty sites, we take another picture of the distribution of the atoms and determine the success of the process of generating fault-free patterns of atoms.If we still have empty sites, we repeat the assembly process once again.We can do it up to 80 times in one go, which is another reason for our ability to generate large flawless configurations with high probability. "

In their study, researchers exploited a large number of traps (361), placed in a 19×19 square grid, which corresponds to a significant number of single atoms (about 200), which allowed them to repeat the assembly process several times. All of these factors ultimately helped them break the previous record of assembling one atom quantum systems.

"The scalability of the physical systems used is essential to keep moving forward in this area," Birkl said. "We have been able to dramatically increase the size of the pattern and the probability of success of neutral-atom-based systems, and no related experiment has shown more than 72 qubits before, so it goes without saying more than 100, or even 111. Our platform has the explicit prospect of being scalable even well beyond these numbers. "

Quantum supremacy typically requires more than 50 qubits, but so far only a few quantum technology experiments have been able to exceed this threshold. In their experience, the researchers reached a total of 111 qubits with a clear plan on how to exceed that number. This is proof of the scalability of their experimental platform.

"In addition, we could enter the regime of quantum supremacy with high success rates because we have demonstrated a success rate of more than 60% for a model with 8 x 8 = 64 qubits," added Birkl. "With the duration of an experimental cycle of one second, this gives a new flawless configuration for quantum processing in the regime of quantum supremacy every two seconds."

The study by Birkl and his team could have important implications for several subdomains of quantum technology research, including quantum simulation and quantum computing. Researchers are now considering transforming their platform into 1000 quantum systems, adding the ability to initiate two qubit quantum gates between atoms to create a two-dimensional quantum processor based on Rydberg's interactions. In this way, they also hope to implement large-scale quantum computing and quantum simulation with the help of their experimental platform.

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