Optimization for configurable, parallel, error-robust entangling gates for trapped atomic ions

Schematic depiction of gate configurability and modulation technique.

The team of researchers (including people from Q-CTRL) has studied a class of entangling gates for trapped atomic ions and demonstrated the use of numeric optimization techniques to create a wide range of fast, error-robust gate constructions.

Their approach introduces a framework for numeric optimization using individually addressed, amplitude and phase modulated controls targeting maximally and partially entangling operations on ion pairs, complete multi-ion registers, multi-ion subsets of large registers, and parallel operations within a single register.

Their calculations and simulations demonstrated that the inclusion of modulation of the difference phase for the bichromatic drive used in the Mølmer-Sørensen gate permits approximately time-optimal control across a range of gate configurations, and when suitably combined with analytic constraints can also provide robustness against key experimental sources of error.

The team further demonstrated the impact of experimental constraints such as bounds on coupling rates or modulation band-limits on achievable performance. Using a custom optimization engine based on TensorFlow, they also demonstrated time-to-solution for optimizations on ion registers up to 20 ions of order tens of minutes using a local-instance laptop, allowing computational access to system-scales relevant to near-term trapped-ion devices.

The study is available here.