Both IonQ and Quantinuum announced news highs in one qubit quality metric called SPAM. This measurement determines how accurately a quantum computer can set a qubit into its initial state and then measure the result at the end. This is one of several important measures that will determine the overall accuracy of the quantum calculations. Other critical measures include single qubit gate fidelity and two-qubit gate fidelities. All of these metrics need to be improved to levels exceeding 99.9% fidelity before error correction can be effectively implemented.

In today’s announcements, IonQ announced that it has achieved a SPAM fidelity level of 99.96% from a previous level of 99.5% which represents about a 13 times reduction in errors. (e.g. A reduction from 50 errors for every 10,000 operations to 4 errors in 10,000). And then a few hours later, Quantinuum announced that they had achieved a level of 99.9904% which is an improvement from the 99.70% level they cited in a news release in July 2021. For comparison, the best number for measurement error in a superconducting based machine that we track on our Qubit Quality page is 99.86%.

Both of these results have been produced on next generation machines that are using the element Barium for the ions. This is a switch from the Yterbium currently used in the production machines both companies are making available to users now. Quantinuum has indicated they are using the 137Ba+ isotype of Barium while IonQ has not specified which specific isotype they are using.

For more on these announcements, you can view a news release from IonQ about their results here and a blog post titled “Deep Dive: State Preparation & Measurement with Barium Qubits” that can be found here. Quantinuum’s press release has been posted on their website here and a technical preprint paper with their results can be seen here.

March 3, 2022