Practicality of training a quantum-classical machine in the noisy intermediate-scale quantum era

Advancements in classical computing have propelled machine learning applications, yet inherent limitations persist in terms of energy, resource, and speed. Quantum machine learning offers a promising avenue to overcome these limitations but poses its own hurdles. This experimental study investigates the training limits of a real quantum-classical hybrid system on an ion-trap platform using supervised protocols. It addresses the challenges of coupling ion-trap systems with classical processors and highlights the effectiveness of genetic algorithms for NISQ devices and complex binary classification tasks with many local minima. The analysis reveals why gradient-based methods may not be ideal in the NISQ era. Our results provide insights into optimizing hybrid quantum-classical systems, emphasizing the importance of training strategies and hardware design. This work not only enhances understanding of such systems but also illustrates their practical potential in solving real-world problems without relying on classical simulators, bridging the gap between quantum and classical computing paradigms.