When the Impossible Becomes Possible: Quantum Tunnelling Wins the 2025 Nobel Prize in Physics

 

How three scientists proved quantum mechanics works on a scale we can see—and changed computing forever

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Imagine throwing a ball at a wall. In our everyday world, the ball bounces back. But what if, occasionally, the ball passed straight through the wall as if it weren't even there? Impossible, right? Not in the quantum world.

This bizarre phenomenon—called quantum tunneling—just earned three physicists the 2025 Nobel Prize in Physics. And their groundbreaking work didn't just prove that tunneling exists; it showed that quantum mechanics can operate on scales much larger than anyone thought possible.

The 2025 Nobel Laureates

On October 7, 2025, the Royal Swedish Academy of Sciences announced that John Clarke, Michel H. Devoret, and John M. Martinis would share this year's Nobel Prize in Physics for their discovery of macroscopic quantum mechanical tunneling and energy quantization in electric circuits.

Their experiments in the mid-1980s fundamentally changed our understanding of where quantum mechanics ends and classical physics begins—and opened the door to today's quantum computers.

What Is Quantum Tunneling?

At the heart of quantum mechanics is a strange truth: particles don't have definite positions. Instead, they exist as probability waves spread across space. This wave-like nature allows particles to do something classically impossible—pass through barriers they shouldn't be able to cross.

Think of it like this: if you roll a ball toward a hill but don't give it enough energy to reach the top, it rolls back down. But a quantum particle, behaving as a wave, has a small probability of appearing on the other side of the hill without ever going over it. It "tunnels" through.

Physicists had known about tunneling in individual atoms and electrons since the early days of quantum mechanics. But could entire systems—collections of billions upon billions of particles—exhibit this ghostly behavior?

The Breakthrough: Quantum on a Macro Scale

In 1984 and 1985, working independently, the three laureates conducted experiments that answered this question with a resounding yes.

Using superconducting circuits cooled to near absolute zero, they created systems where quantum effects could be observed not just in single particles, but in electrical circuits containing countless particles acting in concert. They demonstrated that these macroscopic systems could tunnel between different energy states—escaping from one configuration to another by passing through barriers that classical physics said should be impenetrable.

The laureates showed that their circuits behaved exactly as quantum mechanics predicted, exhibiting discrete energy levels (quantization) and the ability to tunnel between states. When the system tunneled to a new state, a voltage would suddenly appear—physical proof that quantum mechanics was operating on a scale we could measure and observe.

Why This Matters: The Quantum Computing Revolution

The laureates' work wasn't just theoretical—it laid the foundation for modern quantum computing.

Superconducting qubits, the building blocks of many of today's most advanced quantum computers, directly rely on the principles these scientists demonstrated. The Josephson junctions at the heart of these qubits use quantum tunneling to create the delicate quantum states that make computation possible.

Without understanding how to control and harness macroscopic quantum tunneling, the quantum computers being developed by companies like IBM, Google, and others simply wouldn't exist.

From the Lab to the Future

John Clarke, an emeritus professor at UC Berkeley who has been on the faculty since 1969, continues to inspire new generations of physicists. Michel Devoret, now at Yale University, and John Martinis, who led Google's quantum computing efforts before joining UC Santa Barbara, have spent decades building on their foundational discoveries.

Their work bridges the quantum and classical worlds in ways that were once thought impossible. They showed us that the weird rules of quantum mechanics don't just govern the invisible realm of atoms—they can be demonstrated, controlled, and harnessed in circuits we can hold in our hands.

The Big Picture

Quantum tunneling reminds us that reality is far stranger than our everyday experience suggests. A particle can be in two places at once. It can pass through solid barriers. And collections of trillions of particles can act as single quantum objects, following rules that seem to defy common sense.

The 2025 Nobel Prize in Physics celebrates not just a theoretical triumph, but a practical one. The laureates didn't just prove quantum mechanics works at larger scales—they showed us how to use it.

As quantum computers continue to develop, promising to solve problems beyond the reach of classical machines, we owe a debt to the three scientists who, forty years ago, demonstrated that the quantum world could be coaxed into revealing its secrets on our scale.

Sometimes, impossibility is just a barrier waiting to be tunneled through.