Geometric Noise Suppression in Superconducting Qubits via Node-Synchronized Figure-8 Control with Adaptive Phase Tracking

We present experimental validation of a software-defined geometric noise suppression protocol on a commercial superconducting quantum processor (Rigetti Ankaa-3 via AWS Braket). The protocol combines three elements: (1) time-reversal symmetric Figure-8 control pulses that create closed trajectories in parameter space, (2) node-synchronized stroboscopic readout that gates measurements at loop-closure times, and (3) adaptive phase tracking that compensates for environmental drift. Key experimental results include: break-even threshold exceeded with +10 percentage point improvement over baseline idle; phase-dependent noise suppression achieving +82 percentage point improvement through optimal phase selection; and discovery of amplitude-phase coupling (APC) where optimal phase shifts by ≈ 0.9 rad per unit amplitude change. This coupling, interpretable as an environmentally-induced Berry connection in control parameter space, explains why conventional fixed-parameter calibration fails at varying drive strengths. The adaptive protocol successfully tracks environmental drift, recovering from 13% to 85% fidelity autonomously. These results demonstrate that geometric structure in quantum control can be exploited for robust, hardware-agnostic noise suppression without physical device modification.