Combining Trapped Atoms and Photonics to Create New Quantum Devices

Quantum information systems offer faster, more efficient computational methods than standard computers, helping to solve many of the world’s most difficult problems. But fulfilling this ultimate promise will require larger and more interconnected quantum computers than scientists have yet built. Scaling quantum systems to larger sizes and connecting multiple systems has proven challenging.

Now, researchers at the University of Chicago’s Pritzker School of Molecular Engineering (PME) have discovered how to combine two powerful technologies—trapped-atom systems and photonic devices—to create advanced systems for quantum computing, simulation, and cross-linking. The new combination will enable the construction of large quantum systems that can be easily scaled up by using photonics to connect individual systems of atoms.

“We have combined two technologies that have not had much in common in the past,” said Hannes Bernien, assistant professor of molecular engineering and senior author of the new paper published in Nature communication“It’s not only fundamentally interesting 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 to build quantum processors. These lattices of neutral atoms, when excited in a specific sequence, enable complex quantum computations that can scale to thousands of qubits. But their quantum states are fragile and can be easily disrupted—including by photonic devices that aim to collect data in the form of photons.

“Interfacing atomic systems with photonic devices has been quite difficult because of the fundamental differences in the technologies. Atomic system technology relies on lasers to generate and compute them,” says Shankar Menon, a PME graduate student and co-author of the first paper. “Once you expose the system to a semiconductor or photonic system, the lasers scatter, causing problems with atom trapping, detection and computation.”

In the new work, Bernien’s group has developed a new semi-open chip geometry that allows for the interface of atomic systems with photonic chips, which overcomes these challenges. With the new platform, quantum computations can be performed in the computational region, and then a small fraction of those atoms containing the desired data is transferred to a new interconnection region for integration onto the photonic chip.

“We have two separate regions between which atoms can move, one away from the photonic system to perform computations, and one near the photonic system to connect multiple atomic systems,” explains co-author Noah Glachman, a PME graduate student. “The way this system is designed minimizes its interaction with the computational region of the atomic system.”

In the interconnect region, a qubit interacts with a microscopic photonic device that can extract a photon. The photon can then be transmitted to other systems via optical fibers. Ultimately, this means that multiple atomic arrays can be connected to create a larger quantum computing platform than is possible with a single array.

An additional advantage of the new system — which could lead to exceptionally fast computing capabilities — is that multiple nanophoton cavities can be simultaneously attached to a single array of atoms.

“We can have hundreds of these cavities at once, and they can all transmit quantum information at the same time,” Menon said. “That leads to a huge increase in the speed at which information can be shared between connected modules.”

Although the team has demonstrated the feasibility of trapping an atom and moving it between regions, they plan to continue researching other steps in the process, including collecting photons from nanophotonic cavities and generating entanglement over long distances.