The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics 2025 to a trio of scientists for their work on quantum technology.

John Clarke from the University of California, Berkeley USA; Michel H. Devoret from Yale University, New Haven and University of California, Santa Barbara USA; and John M. Martinis from the University of California, Santa Barbara USA were awarded the prize “for the discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit.”

The Academy said the transistors in computer microchips are one example of the established quantum technology that surrounds us, adding that this year’s Nobel Prize in Physics has provided opportunities for developing the next generation of quantum technology, including quantum cryptography, quantum computers, and quantum sensors.

The Nobel Prize laureates conducted experiments with an electrical circuit in which they demonstrated both quantum mechanical tunnelling and quantised energy levels in a system big enough to be held in the hand.

Quantum mechanics allows a particle to move straight through a barrier, using a process called tunnelling, but as soon as large numbers of particles are involved, quantum mechanical effects usually become insignificant.

The Academy said the laureates’ research demonstrated that quantum mechanical properties can be made concrete on a macroscopic scale.

In 1984 and 1985, Clarke, Devoret and Martinis conducted a series of experiments with an electronic circuit built of superconductors, which are components that can conduct a current with no electrical resistance.

In the circuit, the superconducting components were separated by a thin layer of non-conductive material, a setup known as a Josephson junction.

By refining and measuring all the various properties of their circuit, they were able to control and explore the phenomena that arose when they passed a current through it.

Together, the charged particles moving through the superconductor comprised a system that behaved as if they were a single particle that filled the entire circuit.

This macroscopic particle-like system is initially in a state in which current flows without any voltage. The system is trapped in this state, as if behind a barrier that it cannot cross. In the experiment the system showed its quantum character by managing to escape the zero-voltage state through tunnelling.

The system’s changed state is detected through the appearance of a voltage.

The Academy said the laureates could also demonstrate that the system behaves in the manner predicted by quantum mechanics as it is quantised, meaning that it only absorbs or emits specific amounts of energy.

“It is wonderful to be able to celebrate the way that century-old quantum mechanics continually offers new surprises,” said Olle Eriksson, chair of the Nobel Committee for Physics. “It is also enormously useful, as quantum mechanics is the foundation of all digital technology.”

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