The Nobel prize in physics 2025 has been awarded to British, French and American scientists for pioneering experiments that paved the way for the next generation of quantum technologies.
John Clarke, a British physicist based at the University of California at Berkeley, Michel Devoret, a French physicist based at Yale University, and John Martinis, of the University of California Santa Barbara, shared the 11m Swedish kronor (about £871,400) prize announced by the Royal Swedish Academy of Sciences in Stockholm.
The trio led a series of experiments that demonstrated that the bizarre properties of the quantum world can translate into measurable effects in macroscopic electrical circuits. This included a demonstration that so-called quantum tunnelling – the equivalent of a ball passing straight through a brick wall – can occur in superconducting electrical circuits.
The scientists were honoured for the “discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit”, which paved the way for the development of quantum cryptography and quantum computers.
Speaking at a press conference, Prof Clarke, who had only learned of the award through a phone call, said it had never occurred to him that the breakthrough could be awarded the Nobel prize. He said: “To put it mildly, it was the surprise of my life. I’m completely stunned.”
“This is something that … led to the development of the quantum computer,” added Clarke, in whose lab at Berkeley the experiments took place in the 1980s. “It’s recognised that our discovery is, in many ways, the basis of this.”
Quantum theory was developed initially in the early 20th century to explain the physics of the atomic realm, an invisible world that operates on a scale too small to be observed through a microscope. In the quantum world, a particle trapped in an energetic well can “tunnel” its way to freedom, even if it does not have enough energy to climb out.
Working in Clarke’s Berkeley lab, where Devoret had joined as a postdoc and Martinis as a doctoral student, the team began investigating whether similar phenomena might occur at a macroscopic scale in superconductors. In superconductors, current flows with no resistance and this means the electrons are expected to behave in synchrony.
This means that, theoretically, the electrons in a superconductor can be thought of as a single, giant particle filling the entire circuit – but it was not known whether this would translate to them possessing the quantum behaviours seen in particles at an atomic scale.
The experiments focused on a component known as the Josephson junction, in which two superconductors are joined together with a thin insulating barrier between them. According to classical physics, the two sides of the junction are isolated from each other. However, the scientists found that the entire system was able to tunnel through the Josephson junction, causing a voltage to appear across the barrier.
By studying how long it took for the voltage blip to occur, they also showed that this macroscopic tunnelling followed the same probability-based rules as well-known quantum phenomenon such as the decay of radioactive nuclei.
“This work kickstarted the idea that we could get control over the quantum world,” said Dr Malcolm Connolly, who researches quantum behaviour of materials at Imperial College London. “Their discoveries of tunnelling and energy quantisation laid the foundation for today’s superconducting qubits, one of the leading platforms in the global race to build practical quantum computers.”
Superconducting circuits are one of the techniques being explored in attempts to construct a future quantum computer and, in 2014, Martinis and his team were hired by Google to build the first useful quantum computer (he resigned from his role at Google in 2020).
“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.”
