Abstract
- A classical computer with N bits at any given moment is in one of its possible 2N states. - In contrast, the state of the hypothetical quantum computer with N qubits is defined by the values of 2N continuous parameters, the quantum amplitudes. - To beat your laptop in performing some special tasks, like factoring very large numbers, one needs ∼1000 qubits. - Accordingly, the number of continuous variables that should be under our control is at least 21000 ∼ 10300. - Thus the answer to the question in the title is: as soon as physicists and engineers will learn to control thus number of degrees of freedom, which means NEVER.