During a series of experiments in the mid-80s, the three scientists demonstrated quantum mechanics on a circuit big enough to be held in one’s hand.
Three scientists from the UK, France and the US have been awarded the 2025 Nobel Prize in Physics today (7 October) for their macroscopic quantum mechanics experiments.
John Clarke, Michel H Devoret and John M Martinis were awarded the prestigious prize for their work on a series of 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.
In physics, quantum tunnelling is a phenomenon in which an object or particle such as an atom or electron can pass through an energy barrier that, according to classical mechanics, shouldn’t be passable due to the particle not having enough energy.
When large amounts of particles become involved, quantum mechanical effects usually become insignificant. What the new trio of laureates demonstrated, however, was that quantum mechanical properties can be made concrete on a macroscopic scale.
The experiments, conducted in 1984 and 1985, were performed using an electronic circuit built with two superconductors – components that can conduct a current with no electrical resistance.
In the circuit, the superconducting materials were separated by a thin layer of non-conductive material in a set-up known as a Josephson junction. By refining and measuring the circuit’s various properties, Clarke, Devoret and Martinis could control and observe phenomena that occurred when they passed a current through it.
The scientists observed a phenomenon in which all the charged particles in the superconductor behaved in unison, as if they were a single particle that filled the entire circuit.
This ‘particle-like’ system is initially in a state in which current flows without any voltage – a state that the system is trapped in, as if behind a ‘barrier’ that it cannot cross.
During the experiment, the system showed its quantum qualities by escaping the zero-voltage state through quantum tunnelling. The scientists were able to detect the system’s changed state by observing the appearance of voltage.
The trio also demonstrated how the system behaved in a manner predicted by quantum mechanics, by showing that the system is quantised, which means it only absorbs or emits energy in specific amounts.
“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.”
According to the Nobel Committee, the achievement of Clarke, Devoret and Martinis has provided opportunities for developing the next generation of quantum technology, including quantum cryptography, quantum computers and quantum sensors.
“To put it mildly, it was the surprise of my life,” said Clarke on receiving the award during the livestream of this morning’s announcement in Stockholm.
“Monsieur Devoret and John Martinis are brilliant people,” he added. “This discovery would never have happened without the two of them. Their contributions are just overwhelming.”
Last year, the Nobel Prize in Physics was awarded to John Hopfield and Geoffrey Hinton for their contributions towards AI and machine learning research.
Yesterday, the 2025 Nobel Prize awards kicked off with Mary E Brunkow, Fred Ramsdell and Shimon Sakaguchi receiving the Nobel Prize in Physiology or Medicine for their discoveries relating to peripheral immune tolerance.
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