Southwest Quantum Information and Technology

Realization of robust, high-fidelity gates for single-ion qubits in a surface trap

Presenting Author: Daniel Lobser, Sandia National Labs
Contributing Author(s): Matthew G. Blain, Robin Blume-Kohout, Kevin Fortier, Jonathan Mizrahi, Erik Nielsen, Kenneth Rudinger, Jonathan D. Sterk, Daniel L. Stick, Peter Maunz

Single-ion qubits confined to microfabricated surface traps boast numerous advantages for a scalable quantum computer. The flexibility of modern chip traps supports a variety of exotic trapping geometries and unprecedented control over individual qubits. Since their inception, the viability of chip traps has met with skepticism owing to the fact that heating rates would presumably be dominated by surface interactions, which play a larger role as a result of the trap's close proximity to the ions. In order to debunk this misconception, we report on the realization of high-fidelity quantum information processing protocols in Sandia’s High Optical Access (HOA) surface trap. Through a number of technical improvements, such as drift control of classical control parameters and our development of a novel “gapless” pulse technique, we have achieved single-qubit gate fidelities, both laser- and microwave-based, comparable to those found in the best-of-breed electrode traps. Gate Set Tomography (GST) provides an extremely accurate characterization of our gates, including concrete measurements of diamond norm distances. We also demonstrate a realization of the Mølmer-Sørensen two-qubit gate that is stable for several hours. By virtue of this stability, we've performed the first GST measurements in a qutrit basis, which have yielded a two-qubit process fidelity of 99.58(6)%. 

(Session 5 : Thursday from 5:00 - 7:00 pm)