Quantum Computing and Digital Computing
Robert W. Keyes · IEEE Transactions on Electron Devices · 2010
Electronic systems that contain a large number of solid-state devices must deal with the fact that there are likely to be differences between nominally identical components. Methods for manufacturing solid-state devices do not produce highly reproducible products, and solid-state devices change with age and use. Quantum computing systems propose to use the same binary digital language to represent information and describe operations. However, quantum computing is not truly digital; each qubit supplies a signal that depends on its properties rather than being obtained from some standard that is known throughout the system to which it belongs. Quantum computing hardware does not form zeros and ones in some standard way that insures that a signal will be properly interpreted in another place in the system to which it belongs. This absence of a way to produce a truly digital signal leaves quantum logic at the mercy of variability in devices.