The manipulation of neutral atoms by light is one of the most important scientific discoveries in the field of quantum physics in the last three decades. Researchers show that increasing the number of trapped atoms will enable solutions for more complex use cases, such as optimization problems and quantum simulations of intricate systems.

A Leap Towards Scalable Quantum Processors
Quantum computing has always been a field teeming with promises and challenges. Recently, Pasqal, a leading quantum computing company, made a significant stride by successfully loading over 1,000 atoms in a single shot within their quantum computing setup. This breakthrough is seen as a monumental leap towards creating scalable quantum processors capable of solving complex problems beyond the reach of classical computers.

Pasqal’s approach involves building quantum processors from ordered neutral atoms in 2D and 3D arrays. Their latest achievement included the successful trapping of 1,110 atoms within 2,000 traps and demonstrating atom-by-atom rearrangement of an 828-atom target array using optical tweezers. This large-scale trapping is crucial for developing quantum processors that can handle intricate optimization problems and quantum simulations efficiently.

The Science Behind the Feat
In Pasqal’s quantum computing architecture, atoms are confined and manipulated using electromagnetic fields. These atoms’ internal energy states serve as the quantum states of the qubits, which are manipulated to perform quantum operations and execute quantum algorithms. This technique relies on trapping single rubidium atoms in large arrays of optical tweezers, comprising up to 2,088 sites, within a cryogenic environment at a temperature of 6 Kelvin.

This method involves innovative optical designs that combine ultra-high-vacuum-compatible microscope objectives at room temperature with windowless thermal shields, ensuring efficient trapping at cryogenic temperatures. Notably, Pasqal demonstrated atom-by-atom rearrangement of an 828-atom target array using moving optical tweezers controlled by a field-programmable gate array (FPGA).

The Implications and Future Prospects
This achievement underscores the feasibility of large-scale neutral atom quantum computing, enhancing the potential to solve complex optimization problems and conduct quantum simulations. As the number of qubits increases, so does the computational power, allowing quantum processors to tackle problems that classical computers cannot handle.

The significance of this research lies in its scalability. With the successful trapping of over 1,000 atoms, Pasqal is paving the way for quantum processors with over 1,000 qubits, with future targets of 10,000 qubits by 2026-2027. The draft research paper detailing this work is titled “Rearrangement of single atoms in a 2000-site optical tweezers array at cryogenic temperatures.”

A Collaborative Breakthrough in Quantum Computing
Adding to the excitement in the quantum realm, researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have discovered a way to combine two powerful technologies—trapped atom arrays and photonic devices. This combination promises to yield advanced systems for quantum computing, simulation, and networking, enabling the construction of large quantum systems that can be easily scaled up.

“We have merged two technologies which, in the past, have really not had much to do with each other,” said Hannes Bernien, Assistant Professor of Molecular Engineering and senior author of the new work, published in Nature Communications. “It is not only fundamentally interesting to see how we can scale quantum systems in this way, but it also has a lot of practical applications.”

Arrays of neutral atoms trapped in optical tweezers—highly focused laser beams that can hold the atoms in place—are an increasingly popular way of building quantum processors. These grids of neutral atoms, when excited in a specific sequence, enable complex quantum computation that can be scaled up to thousands of qubits. However, their quantum states are fragile and can be easily disrupted—including by photonic devices that aim to collect their data in the form of photons.

Overcoming Challenges with Innovative Solutions
Connecting atom arrays to photonic devices has been challenging due to the fundamental differences in the technologies. Atom array technology relies on lasers for their generation and computation. “As soon as you expose the system to a semiconductor or a photonic chip, the lasers get scattered, causing problems with the trapping of atoms, their detection, and the computation,” explained Shankar Menon, a PME graduate student and co-first author of the new work.

To overcome these challenges, Bernien’s group developed a new semi-open chip geometry that allows atom arrays to interface with photonic chips. This new platform enables quantum computations to be carried out in a computation region, after which a small portion of the atoms containing desired data are moved to a new interconnect region for photonic chip integration.

“We have two separate regions that the atoms can move between, one away from the photonic chip for computation and another near the photonic chip for interconnecting multiple atom arrays,” explained co-first author Noah Glachman, a PME graduate student. “The way this chip is designed, it has minimal interaction with the computational region of the atom array.”

A Future of Interconnected Quantum Systems
In the interconnect region, the qubit interacts with a microscopic photonic device, which can extract a photon. The photon can then be transmitted to other systems through optical fibers. This innovation means that many atom arrays could be interconnected to form a larger quantum computing platform than is possible with a single array.

An additional strength of the new system—which could lead to especially speedy computation abilities—is that many nanophotonic cavities can be simultaneously connected to one single atom array. “We can have hundreds of these cavities at once, and they can all be transmitting quantum information at the same time,” said Menon. “This leads to a massive increase in the speed with which information can be shared between interconnected modules.”

While the team demonstrated the feasibility of trapping an atom and moving it between regions, they plan future studies to look at other steps in the process, including the collection of photons from the nanophotonic cavities and the generation of entanglement over long distances.

Conclusion
The advancements by Pasqal and the University of Chicago’s PME are pushing the boundaries of quantum computing. With the successful large-scale trapping of atoms and the innovative integration of atom arrays with photonic devices, the future of quantum computing looks promising. These breakthroughs not only enhance our understanding of quantum mechanics but also bring us closer to realizing practical and scalable quantum systems.