The 2025 Nobel Prize in Physics was awarded to three scientists for their experimental discoveries on macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit. The laureates are:
- John Clarke — UK-born physicist, Professor Emeritus, University of California, Berkeley
- Michel H. Devoret — French physicist, Yale University and University of California, Santa Barbara
- John M. Martinis — American physicist, University of California, Santa Barbara
The Royal Swedish Academy of Sciences announced the prize on 7 October 2025. The trio share the SEK 11 million prize equally. Their work, conducted across the 1980s, established that quantum-mechanical behaviour — long understood as a feature of microscopic systems like atoms and electrons — could be observed in macroscopic electric circuits visible to the naked eye. This finding seeded the field of superconducting quantum computing, which today underpins the quantum processors of Google, IBM, Rigetti, and other industry players.
What the work showed
In the early 1980s, the prevailing assumption in solid-state physics was that quantum effects were confined to systems with very small numbers of particles. A wire carrying a current — even one made from a superconductor — was assumed to behave classically because of the vast number of electrons involved.
Clarke, Devoret, and Martinis showed otherwise. Working at UC Berkeley, they constructed an electrical circuit containing a Josephson junction — a thin insulating barrier between two superconductors — and demonstrated two distinctly quantum phenomena:
Macroscopic quantum tunnelling
In a classical picture, an electric current trapped in a superconducting loop cannot escape unless given enough energy to overcome a confining barrier. The Berkeley group showed that the macroscopic current state of the entire circuit could *tunnel* through the barrier without classical energy supply — exactly the way an individual electron can tunnel through a thin barrier in atomic physics. The tunnelling involved an effectively macroscopic quantum object, not a single particle.
Energy quantisation
The same Josephson-junction circuit exhibited discrete, quantised energy levels — like the discrete energy levels of an atom — rather than the continuum of states classical theory predicts for a macroscopic system. The Berkeley team measured the spacing between these levels and showed they conformed to quantum-mechanical predictions.
Together, these results demonstrated that the entire macroscopic electrical state of a circuit could behave as a quantum object: a *macroscopic quantum state* that could be prepared, manipulated, and measured.
Why the discovery matters
The macroscopic quantum tunnelling experiments turned out to be the experimental foundation of an entire subsequent field.
The qubit
A superconducting circuit with quantised energy levels can serve as a quantum bit (qubit) — the basic unit of a quantum computer. The two lowest energy levels can encode the |0⟩ and |1⟩ states of a qubit, while the wavefunction’s phase encodes quantum superposition and entanglement. The Berkeley experiments established that such states could be reliably prepared and read out in a circuit.
Quantum computing platforms
Google’s Sycamore processor (which demonstrated quantum supremacy in 2019), IBM’s Eagle and Condor processors, and Rigetti Computing’s quantum chips are all built around the transmon — a particular type of superconducting qubit derived from the Josephson-junction architecture Clarke, Devoret, and Martinis first explored.
Quantum sensing
Beyond computing, the same macroscopic quantum behaviour underpins ultra-sensitive SQUID magnetometers (Superconducting Quantum Interference Devices) used in neuroscience, geological exploration, and dark-matter detection. Clarke himself has been a long-standing contributor to SQUID research.
The laureates’ subsequent careers
John Clarke
Born 1942 in Cambridge, UK. BA in physics (1964) and PhD (1968) from Cambridge. He joined UC Berkeley as a postdoctoral researcher in 1968 and became a faculty member, retiring as the Karl A. van Bibber Professor Emeritus of Physics. Clarke’s later work on SQUIDs, magnetic resonance imaging at ultra-low fields, and dark-matter axion searches has been continuously influential. He was awarded the Royal Society’s Hughes Medal (2004) and the Comstock Prize in Physics (1999).
Michel H. Devoret
Born 1953 in Paris. Trained at École Normale Supérieure and Paris-Sud University. After collaboration with Clarke at Berkeley, Devoret returned to France to establish the Quantronics group at CEA Saclay, which built some of the most precise superconducting-qubit experiments of the 1990s. He moved to Yale University in 2002 and subsequently to UC Santa Barbara. He is widely credited as one of the chief architects of the transmon qubit.
John M. Martinis
Born 1958 in San Francisco. PhD from UC Berkeley in 1987 under Clarke’s supervision. After positions at CEA Saclay (with Devoret) and the National Institute of Standards and Technology (NIST), Martinis joined UC Santa Barbara and from 2014 led the Google Quantum AI hardware team. He oversaw the development of the Sycamore processor, which in 2019 carried out a calculation in 200 seconds that the team estimated would have taken the world’s fastest classical supercomputer thousands of years — the first claim of “quantum supremacy”.
How this fits the broader 2025 Nobel slate
The Royal Swedish Academy announced other 2025 Nobel laureates over the same week:
- Physiology or Medicine — Mary E. Brunkow, Fred Ramsdell, and Shimon Sakaguchi for discoveries on peripheral immune tolerance
- Chemistry — Susumu Kitagawa, Richard Robson, and Omar Yaghi for the development of metal-organic frameworks
- Literature — László Krasznahorkai
- Peace — María Corina Machado
- Economic Sciences — Joel Mokyr, Philippe Aghion, and Peter Howitt for innovation-driven economic growth
Both Clarke (Physics) and Robson (Chemistry) were UK-born. Joel Mokyr was Dutch-born but professor at Northwestern, an American university.
What it means for quantum computing
The 2025 Physics Nobel is the most direct recognition the quantum-computing field has received. With major investments from Google, IBM, Microsoft, Amazon, China’s national programmes, and India’s National Quantum Mission (₹6,000 crore), the field is now squarely industrial. The Berkeley experiments of the 1980s — laboratory-bench measurements involving microvolt signals at near-absolute-zero temperatures — turn out to be the cornerstone of a multi-billion-dollar global research and engineering enterprise.
FAQs
Who won the 2025 Nobel Prize in Physics?
John Clarke (UK-born, UC Berkeley), Michel H. Devoret (French-born, Yale and UC Santa Barbara), and John M. Martinis (American, UC Santa Barbara), for experimental discoveries on macroscopic quantum tunnelling and energy quantisation in an electric circuit.
What is macroscopic quantum tunnelling?
The phenomenon where the entire macroscopic electrical state of a circuit — typically a superconducting loop with a Josephson junction — can quantum-mechanically tunnel through a confining barrier, just as an individual electron can tunnel through a thin atomic barrier.
Why is this important for quantum computing?
Because the same superconducting circuits that exhibit macroscopic quantum tunnelling can be configured as qubits. The transmon — the dominant qubit architecture in Google, IBM, and Rigetti quantum processors — is a direct descendant of the Josephson-junction circuits Clarke, Devoret, and Martinis studied.
What is a Josephson junction?
A thin insulating barrier between two superconductors. It is a fundamental building block of superconducting electronics and the heart of both qubits and SQUID magnetometers.
Where did John Clarke study?
Cambridge University, UK — BA in 1964 and PhD in 1968. He moved to UC Berkeley as a postdoctoral researcher in 1968 and remained there as a faculty member until retirement.
What did John Martinis do after the Berkeley work?
He led the Google Quantum AI hardware team from 2014, overseeing the development of the Sycamore processor that claimed quantum supremacy in 2019. He has since continued quantum-hardware research at UC Santa Barbara.
Who else won Nobel Prizes in 2025?
Brunkow-Ramsdell-Sakaguchi (Medicine), Kitagawa-Robson-Yaghi (Chemistry), Krasznahorkai (Literature), Machado (Peace), and Mokyr-Aghion-Howitt (Economic Sciences).
How does this Nobel connect to India’s National Quantum Mission?
India’s NQM (launched 2023, ₹6,000 crore) targets intermediate-scale quantum computers with 50-1000 physical qubits — the precise computing platform the 2025 Nobel work enabled. Indian research at the Tata Institute of Fundamental Research, IISc Bengaluru, IIT Madras, and the Raman Research Institute uses superconducting qubit architectures derived from this foundational work.
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