'X', born in the UK, was conferred the Nobel Prize in 2025. He was a professor in an American university when this prize was announced. Identify 'X':

John Clarke

John Clarke was born in Cambridge, UK, and was awarded the 2025 Nobel Prize in Physics for work involving macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit. At the time of the announcement, he was Professor Emeritus at the University of California, Berkeley. Michel H. Devoret was born in France, Richard Robson was affiliated with an Australian university, and Joel Mokyr was born in the Netherlands.