The Royal Swedish Academy of Sciences has awarded the 2025 Nobel Prize in Physics to John Clarke, Michel H. Devoret and John M. Martinis. The award recognizes experiments that demonstrated quantum effects such as tunneling and quantized energies in an electronic circuit on a macroscopic scale.

This year's Nobel laureates conducted experiments with an electrical circuit large enough to be held in the hand, demonstrating both quantum mechanical tunnelling and quantized energy states. In quantum mechanics, a particle can pass through a barrier - an effect known as tunneling. In large systems, such quantum effects do not normally occur. However, the experiments made these properties visible on a macroscopic level.

Between 1984 and 1985, John Clarke, Michel H. Devoret and John M. Martinis investigated a circuit made of superconductors that conduct electrical current without resistance. In this circuit, the superconducting components were separated from each other by a thin non-conducting layer, a so-called Josephson junction. By precisely measuring and controlling the circuit properties, the researchers were able to investigate the phenomena that occur when current flows through the circuit.

The system of charged particles behaved like a single macroscopic particle that filled the entire circuit. Initially, the system was in a state with no voltage drop, comparable to a particle trapped behind a barrier. The quantum effect was demonstrated by the fact that the system was able to leave this zero-voltage state by tunneling. The change of state became visible through the occurrence of a voltage. In addition, the researchers were able to prove that the circuit reacted in a quantized manner and only absorbed or emitted certain amounts of energy.

"It is wonderful to be able to celebrate the way that century-old quantum mechanics continually offers new surprises. It is also enormously useful, as quantum mechanics is the foundation of all digital technology," says Olle Eriksson, Chairman of the Nobel Committee for Physics. Transistors in computer chips are an established example of the use of quantum mechanical effects.

The prizewinners' work also provides a basis for the further development of the next generation of quantum technologies, including quantum cryptography, quantum computers and quantum sensors.

The award winners

• John Clarke (b. 1942, Cambridge, UK), PhD 1968, University of Cambridge; Professor at the University of California, Berkeley, and University of California, Santa Barbara.
• Michel H. Devoret (b. 1953, Paris, France), PhD 1982, Paris-Sud University; Professor at Yale University and University of California, Santa Barbara.
• John M. Martinis (born 1958, USA), PhD 1987, University of California, Berkeley; Professor at the University of California, Santa Barbara.

Detailed information on the experiments, the quantum mechanical effects and the awards is provided by the Royal Swedish Academy of Sciences. You can download the PDFs below.