Curator's Take
This article tackles a key challenge in trapped Rydberg ion quantum computing, where the promise of ultra-fast gates comes with the trade-off of technical complexity in controlling multiple simultaneous laser and microwave fields. The researchers discovered that running the STIRAP excitation and microwave dressing processes simultaneously creates unwanted interference that degrades gate performance, so they developed a sequential approach that separates these stages to dramatically improve fidelity to over 99.9%. What makes this particularly exciting is the demonstration of a non-adiabatic speed-up that compresses gate times to just 400 nanoseconds while maintaining high fidelity - a crucial combination for building fault-tolerant quantum computers where you need both speed and precision. This work represents the kind of careful pulse engineering that will be essential for translating the theoretical advantages of Rydberg ion systems into practical quantum computing platforms.
— Mark Eatherly
Summary
The strong dipole-dipole interaction of trapped Rydberg ions offers the possibility of sub-microsecond entanglement gates. For example a two-qubit Control-Phase gate in 88 Sr + ions can be realized, by simultaneous excitation to the Rydberg states via stimulated Raman adiabatic passage (STIRAP) with simultaneous microwave induced dipole-dipole interaction. We show that this excitation protocol distorts the dark-state of the STIRAP stage and is prone to decay from the intermediate state. Here, we propose a novel pulse ordering, in which the STIRAP and the microwave dressing of the Rydberg states occurs in separate stages, preventing mutual interference effects that are detrimental to the gate fidelity. We show that, for experimentally feasible parameters, the proposed excitation scheme can achieve a fidelity of 99.93%, surpassing the experimentally demonstrated gate. In addition, we demonstrate a non-adiabatic speed-up to 400 ns by employing asymmetric pulse shapes in the STIRAP stage. The entangling phase is then controlled solely through the interaction strength by nonresonant asymmetric chirping of the microwave field.