Unfortunately, there are no big, stable quantum computers yet, but there are several small, unstable quantum computers that do exist. Researchers call such machines NISQs—Noisy, Intermediate-Scale Quantum Computers. A growing number of These firms are searching for “quantum advantages”—ways in which even today’s limited machines can contribute to their bottom line.
Quantum computers are likely to be expensive machines operated and developed by a small number of companies. Google and IBM, for example, desire to double quantum computer capabilities every year, on Moore’s Law-like basis. Together with a small but significant cohort of promising start-ups, they will increase the number of qubits that can be handled by their computers.
Unfortunately for developers, quantum mechanics itself makes their task more difficult by depriving them of their most straightforward error-correcting tool, copying. In quantum mechanics, a no-cloning theorem says it’s not possible to copy the state of one qubit onto another without altering the state of the first one. “This means that it is not possible to directly translate our classical error correction codes to quantum error correction codes,”