Practical quantum computing requires engineered hardware able to manipulate quantum information encoded in physical systems like photons, electrons, or atoms. Building this functionality involves integrating components like qubits, controllers, amplifiers, modulators, cryogenics, and interconnects as represented in Fig. 14.1. Multiple qubit modalities and architectural approaches are being researched. This chapter discussed prominent quantum computing platforms today and compares their capabilities (Alexeev et al. in PRX Quant 2, 2021 [1]).