Nobel Prize in Physics 2025: quantum tunneling in a palm-sized circuit
The 2025 Nobel Prize in Physics goes to three researchers who literally put quantum mechanics on the lab bench. John Clarke, Michel H. Devoret and John M. Martinis are awarded “for the discovery of macroscopic quantum tunneling and energy quantization in an electrical circuit”.
Their experiments, performed in the mid-1980s at the University of California, Berkeley, showed that quantum effects do not occur only at the level of single atoms and electrons. By using superconducting elements, they built an electrical circuit roughly the size of a thumbnail that behaves like a single “artificial atom”.
What exactly did the laureates do?
Clarke, Devoret and Martinis worked with superconducting circuits cooled to temperatures close to absolute zero. In such a circuit, electrons pair up into Cooper pairs and behave like a single quantum “fluid”.
At the heart of the experiment is a Josephson junction – an ultrathin insulating barrier between two superconductors. Classical physics says that current should not pass through that barrier. Quantum mechanics, however, allows the electron wavefunction to leak through the wall – this is quantum tunneling.
The laureates demonstrated two key things:
- that an entire macroscopic system (a superconducting circuit containing billions of electrons) can tunnel from one energy state to another as if it were a single quantum particle;
- that the energy of the circuit is not continuous, but comes in discrete levels – the circuit absorbs and emits energy in well-defined “quanta”, exactly as quantum theory predicts.
In other words, they created an electrical circuit that behaves as a giant quantum oscillator – a system physically large enough to hold in your hand, but whose behaviour belongs to the world of quantum particles.
Why does it matter today?
When the experiments were done, they were primarily a fundamental test of quantum theory on a macroscopic scale. Today it is clear that these results laid the groundwork for superconducting qubits – the basic building blocks of many modern quantum computers.
Current quantum platforms (Google, IBM and others) use whole families of superconducting circuits that directly build on the pioneering work of Clarke, Devoret and Martinis. What was once an “exotic lab effect” has become core quantum-computing technology.
A Nobel that connects the micro and macro worlds
In its citation, the Nobel Committee highlighted that this prize recognizes “quantum behaviour on a human scale” – showing that the rules of quantum mechanics apply to systems that are:
- large enough to be handled in the lab by hand,
- made of an enormous number of particles,
- yet still display tunneling and discrete energy levels like an atom or molecule.
For readers, the takeaway is simple but powerful: quantum physics is no longer just an exotic theory from textbooks. It is now built into electronic chips, precision metrology, sensors and quantum computers – and that is why the 2025 Nobel Prize in Physics is one of those awards that quietly shifts how we think about the boundary between the “micro” and “macro” worlds.
Note: This article is for informational purposes only and is based on publicly available information from NobelPrize.org and the press release of the Royal Swedish Academy of Sciences.
