In the rapidly evolving world of quantum computing, a groundbreaking study published in the IEEE Transactions on Quantum Engineering, or in English, IEEE Transactions on Quantum Engineering, is set to redefine how we train quantum neural networks (QNNs). Led by Subhadeep Mondal from the G.S. Sanyal School of Telecommunication at the Indian Institute of Technology Kharagpur, this research introduces a novel approach to training QNNs that could have significant implications for industries, including the energy sector.
Quantum neural networks are emerging as powerful tools for quantum machine learning, but their training has been a persistent challenge. Traditional methods, such as quantum multilayer perceptrons, rely on fidelity-based cost functions. While these work well for pure states, they fall short when dealing with mixed states—common in learning quantum channels. “Most existing approaches are not well-suited for mixed states, which are prevalent in real-world quantum systems,” explains Mondal. “This limitation can hinder the accuracy and efficiency of quantum learning.”
The study introduces a relative entropy-inspired cost function that quantifies the directional divergence between learned and target states. Relative entropy, or Kullback-Leibler divergence, provides a more informative and principled measure than linear fidelity, capturing both spectral and eigenvector differences in mixed states. This approach not only preserves the completely positive structure of the network but also supports efficient backpropagation in layered QNN configurations.
The implications of this research are far-reaching. In the energy sector, quantum machine learning can optimize complex systems, from grid management to renewable energy integration. “By improving the training of QNNs, we can enhance the robustness and scalability of quantum learning models,” says Mondal. “This could lead to more efficient and resilient energy systems, ultimately benefiting both consumers and the environment.”
The study also highlights the potential for entropy-based optimization to achieve improved accuracy and convergence over fidelity-based training. This could pave the way for more scalable and noise-resilient quantum learning, addressing one of the key challenges in the field.
As the energy sector continues to explore quantum technologies, this research offers a promising path forward. By leveraging the principles of quantum relative entropy, we can unlock new possibilities for quantum machine learning, driving innovation and efficiency in critical industries. The work published in the IEEE Transactions on Quantum Engineering, a leading journal in the field, underscores the importance of this research and its potential to shape the future of quantum computing.
In a world where quantum technologies are becoming increasingly integral, this study by Mondal and his team represents a significant step forward. It not only advances our understanding of quantum neural networks but also opens up new avenues for practical applications, particularly in the energy sector. As we continue to explore the potential of quantum computing, this research serves as a beacon of innovation and progress.

