It is rare for a director of a start-up in a nascent industry to worry about being too successful. But Ian Hogarth of Phasecraft, a UK quantum algorithms company, sees the day when quantum computing valuations will spiral like those of artificial intelligence companies: “There will be a moment of realisation and we will have to hold our nerve.”

That day may be coming, although quantum computing still remains more of a vision than a reality. Google’s claim to have demonstrated a case of “quantum advantage” — the technology outperforming classical computing — is part of a growing sense that it will shift from experiments to practical use within a few years.

If so, it will pose a challenge to the UK’s quantum computing industry, which has spun out of research at leading universities. Will its promising start-ups be acquired by US technology companies such as Google and IBM, which both have quantum operations, or can they become giants themselves?