How big is a quantum computer?
Sascha Wallentowitz, Ian A. Walmsley, Joseph H. Eberly · arXiv (Cornell University) · 2000
Accounting for resources is the central issue in computational efficiency. We point out physical constraints implicit in information readout that have been overlooked in classical computing. The basic particle-counting mode of read-out sets a lower bound on the resources needed to implement a quantum computer. As a consequence, computers based on classical waves are as efficient as those based on single quantum particles.