Physical-resource demands for scalable quantum computation
Carlton M. Caves, Ivan Deutsch, Robin Blume-Kohout · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2003
The primary resource for quantum computation is Hilbert-space dimension. Whereas Hilbert space itself is an abstract construction, the number of dimensions available to a system is a physical quantity that requires physical resources. Avoiding a demand for an exponential amount of these resources places a fundamental constraint on the systems that are suitable for scalable quantum computation. To be scalable, the number of degrees of freedom in the computer must grow nearly linearly with the number of qubits in an equivalent qubit-based quantum computer.