In Industry First, IonQ to Use Barium Ions for Computation

IonQ has started the work to advance the technology of trapped ion quantum computing beyond the ytterbium ions that we and other researchers have used for years and towards using barium ions for computation in our forthcoming generation of quantum computers. Peter Chapman, IonQ's CEO and President, made the announcement during his keynote address at the 2021 Q2B Practical Quantum Computing Conference.

“IonQ builds the world’s most powerful quantum computers, and the ability to build systems with barium qubits will help us bring our customers even closer to realizing the commercial benefits of quantum,” said Chapman. “We believe the advanced architectures enabled by barium qubits will be even more powerful and more scalable than the systems we have been able to build so far, opening the door to broader applications of quantum computing.”

IonQ was founded in 2015 by physicists Chris Monroe and Jungsang Kim, who both foresaw the potential for trapped ions to serve as efficiently scalable error-corrected quantum computers with greater efficiency than other approaches to quantum computing. Most other types of quantum computing are expected to require hundreds of physical qubits in order to produce a single error-corrected qubit. We believe that trapped ion technology will have a fully-corrected ratio of tens of physical qubits to one logical qubit.

Announcements of quantum systems of over a hundred qubits that don't use trapped ions sound really impressive when nobody is talking about error correction. But at IonQ, we are more interested in making stable, accurate computers that are useful to end users as soon as possible. This is why we've always emphasized development of systems that can truly be optimized rather than race to tout a high, but ultimately meaningless number of physical qubits.

Ytterbium ions have taken us a long way and continue to be important for our systems. We've learned a lot of important techniques for working with ytterbium. Barium ions have an energy structure that is very similar to ytterbium, which will allow us to build on that previous work without reinventing the wheel. And as the world's first quantum computing company to use barium ions for quantum computing, we're going to build on that experience with some really powerful advantages.

One of ytterbium’s characteristics has been the fact that the lasers pointed at them to perform logical gates are ultraviolet. As anyone who has ever left a plastic toy in the backyard all summer has seen, UV rays wear out materials quickly. This happens within a quantum computer as well. Expensive materials like lens coatings are gradually destroyed by ultraviolet lasers.

Moving to barium allows us to use lasers that are not in the ultraviolet spectrum. This means less damage to components and greater use of off-the-shelf components that lower the cost of manufacturing and speed the rate of development. The wavelength of these lasers also allows us to build more compact quantum computers.

These lasers will enable faster speeds and higher gate fidelity in our forthcoming generation of quantum computers. The time taken to perform computations could become noticeably shorter for customers.

Barium and the wavelengths of light that we can use with it will also make it much easier for us to network multiple ion traps. Creating a modular system to link trapped ion processing units is a key component to our strategy for making much more powerful quantum computers.

“We believe that the addition of barium qubits to our systems opens up tremendous technical opportunities for making our systems more scalable, more reliable, and easier to build,” said Jungsang Kim, Co-Founder and CTO of IonQ. “By leveraging the inherent advantages of barium qubits, we are now able to access new features for building advanced quantum computers that will be relevant for solving critical societal problems.”

Most importantly to our customers, the use of barium and conventional lasers can provide better gate fidelity than was possible with ytterbium. With better gate fidelity, calculations will be more accurate and a wider range of applications will be possible. We will continue to work with ytterbium as well as with barium and it is possible that both types of ions could be part of our quantum systems in the future. Decisions about which ions to use will, as always, depend on what turns out to make practical quantum computing work best for our customers as quickly as possible.