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':

The correct answer is C, John Clarke. He was born in Cambridge, England, and is a professor at the University of California, Berkeley.

The 2025 Nobel Prize in Physics went to John Clarke, Michel H. Devoret and John M. Martinis for discovering macroscopic quantum tunnelling and energy quantisation in an electric circuit. Their experiments in the mid-1980s used superconducting circuits large enough to hold in the hand, and showed that such a circuit can behave as a single quantum object. This work laid the ground for the superconducting qubits used in today's quantum computers. Clarke, born in 1942, has spent most of his career at Berkeley, which fits both clues in the question.

A is wrong because Devoret, a co-winner in physics, was born in Paris, France. B is wrong because Richard Robson, a 2025 chemistry laureate for metal-organic frameworks, was born in England but works at the University of Melbourne in Australia. D is wrong because Joel Mokyr, a 2025 economics laureate, was born in the Netherlands.

Exam tip: Physics 2025: Clarke, Devoret, Martinis, quantum tunnelling in a circuit.