The Nobel Prize in Medicine or Physiology is awarded by the Nobel Assembly at the Karolinska Institute in Stockholm.Credit: Beata Zawrzel/NurPhoto via Getty
Three physicists have been awarded the 2025 Nobel Prize in Physics for demonstrating quantum physics on the macroscopic scale.
The research, including into the bizarre phenomena of quantum tunnelling and quantum superposition, has helped to underpin some of today’s most advanced quantum computers.
John Clarke at the University of California, Berkeley, Michel Devoret at Yale University in New Haven, Connecticut, and the University of California, Santa Barbara (UCSB), and John Martinis, also of USCB will share the prize of 11-million Swedish kronor (US$1.2 million), announced by the Royal Swedish Academy of Sciences in Stockholm on 7 October.
“I am completely stunned; it had never occurred to me in any way that this might be the basis for a Nobel Prize,” said Clarke, speaking to journalists gathered for the announcement. “I think that our discovery in some ways is the basis of quantum computing,” he said, adding that although he led the trio’s work in the 1980s, the contributions of the other two were “overwhelming”.
“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,” said Olle Eriksson, a physicist at Uppsala University in Sweden and chair of the Nobel Committee for Physics.
Quantum tunnelling of electrons brings ultrafast optical microscopy to the atomic scale
Macroscopic quantum mechanics
The foundations of quantum mechanics were laid down 100 years ago. But many of its strange implications have taken decades to unravel.
One is the phenomenon of quantum tunnelling — the ability of particles to pass straight through a barrier that shouldn’t be possible according to classical physics, given its energy. Tunnelling explains radioactive decay, in which, despite being confined inside an atom, an alpha particle still has a small probability of escaping the nucleus. Another is quantum superposition, in which an object can exist simultaneously in two states.
Both tunneling and superposition were known at the atomic scale but hadn’t been observed in macroscopic systems. In the late 1970s, Anthony Leggett, who won the 2003 Nobel Prize in Physics for his theoretical work on superconductors, suggested that the phenomena should be observable at the macroscopic scale using superconducting circuits — loops of wire which, when chilled to a fraction of a degree above absolute zero, can conduct electricity without resistance1.
In the 1980s, Clarke, Devoret and Martinis, working at Berkeley, were among those exploring quantum effects in superconducting loops2. The trio set up an experiment in which two superconductors were separated by a thin barrier, known as a Josephson junction3. In this state, a supercurrent can flow with zero resistance, but also no voltage — like a river that runs without friction or a downhill gradient to give it a push. In classical physics, the system would stay stuck like this, unless given enough energy to escape.
