From qubits to general-purpose computing: quantum advantage and its limits
Quantum computing has been championed as a ground-breaking technology due to its significant computational advantage over classical computing systems. At present, fault-tolerant, large-scale universal quantum computing remains elusive, and these issues remain central challenges in engineering, physics, and computer science. In theory, quantum advantage offers the potential to make many currently intractable computational problems practically solvable, with profound implications across science, industry, and computing. This paper examines the contemporary case for general-purpose quantum computing and the prevailing challenges that presently prevent its widespread adoption. It surveys the theoretical foundations of computation and quantum mechanics that underpin quantum computers, describes the quantum computational model and a working implementation on IBM's Qiskit platform, and evaluates the persistent barriers of noise, decoherence, and scalability that constrain quantum systems today. We conclude that quantum computing is best positioned, in the near term, as a specialized co-processor rather than a general-purpose replacement for classical computing.