Architectural Thinking for Hybrid Quantum–Classical Systems: A Decision Playbook and Reference Architecture for Practical Quantum Computing by Kedar Kulkarni

Quantum computing is entering a hybrid era. QPUs — quantum processing units — are starting to work alongside classical HPC infrastructure, not replace it. Think of it like how GPUs first showed up as specialized accelerators before becoming core parts of modern supercomputers. Quantum is following that same path. But here's the thing: today's quantum hardware is noisy, capacity-limited, and far from fault-tolerant. That reality shapes everything. You can't design a useful quantum system without acknowledging what the hardware can and can't do right now. This book is a merged reference that brings together two complementary views: a decision-framework playbook for making smart architectural choices under real constraints, and a technical reference architecture for deploying hybrid quantum-HPC systems in practice. Together, they give you both the 'why' and the 'how.'