Blog-6

‘Tunnelling’ Through Uncertainty: The 2025 Physics Nobel Prize
IBM and Google are already using the science behind this year’s Physics Nobel Prize to power quantum computers. The 2025 award bridged the microscopic and macroscopic worlds and showed why quantum uncertainty now matters to every technologist.

Over the last century, physicists have characterized quantum mechanics as a world that lives behind an invisible curtain – a world in which electrons dance, particles tunnel through walls, and all laws of physics are probabilistic. This year’s Nobel Prize in Physics cuts that curtain right down and puts that quantum weirdness quite literally in human hands.

John Clarke, Michel H. Devoret and John M. Martinis share the prestige of being 2025’s winners "for the discovery of macroscopic quantum mechanical tunnelling and energy quantisation in an electric circuit". Essentially, they were able to demonstrate that a huge, conspicuous object – a coin-sized electronic circuit - could act as an individual quantum particle.

Their experiments showed that the laws of the atomic world can be scaled up to the level of the mundane and that new technologies based on them will govern the next century of computation, sensing and encryption.

Tunnelling through

In quantum space, particles do what marbles and baseballs never could – pass directly through barriers i.e. tunnelling. Think of rolling a ball towards a hill: in classical physics, if it doesn’t have enough energy, it rolls back down. In quantum physics however, there’s a slight possibility it will tunnel through and come out the other side.

This ‘tunnelling’ explains radioactive decay, semiconductors, even nuclear reactions powering our sun. Until the mid-1980s tunnelling had only been observed between particles or atomic systems. But observing the same in a macroscopic environment – a setup with billions of particles acting together – remained elusive.

Clarke, Devoret and Martinis did just that. They built an electrical circuit using superconductors cooled to almost absolute zero and used a thin insulator called a Josephson junction to separate them. Within these superconductors, electrons formed ‘Cooper pairs’ – entangled structures that exist in perfect harmony, losing aspects of their individual identities – allowing the whole circuit to be considered as one ‘superparticle’.

When current was passed through the circuit it went into a trapped, zero-voltage state, like a marble caught in a valley. Sometimes, though, the current would break through the wall of this ‘valley’ and produce a measurable voltage spike. This was macroscopic quantum tunnelling (MQT) - quantum mechanics at human scale.

Source: The Royal Swedish Academy of Sciences

Quantised Energy and the Birth of Artificial Atoms

The researchers then directed microwaves of different frequencies onto the circuit and noted that it could absorb energy in certain quantities. The macroscopic system possessed discrete energy levels, like those of electrons within an atom. This was definite proof of the quantisation of energy in a visible, man-made object.

Their experiments, carefully insulated from heat and electricity, revealed that the phase difference across the Josephson junction could be described as a quantum particle trapped in ‘washboard’ potential. It was a masterpiece of theory leaping into engineering.

Martinis has built superconducting quantum bits, or qubits, to be used in quantum computing experiments at Google. Quantised energy levels and macroscopic tunnelling are now used as the foundations of circuit quantum electrodynamics (cQED) in which artificial atoms, constructed out of circuits, can be manipulated, coupled and read like the real thing.

From Lab to Market

This year’s Nobel might seem abstract to many, but its power is already being felt in quantum computing laboratories and cryogenic data centres all around the world.

Google and IBM are now directly in a race to quantum advantage based on their superconducting circuits. They form the basis of quantum sensors which are capable of detecting small magnetic fields, gravitational waves and vibrations of molecular particles. Ultra-sensitive medical imaging and navigation systems also widely use quantum tunnelling diodes and Josephson Junction arrays.

The laureates’ work effectively showed that we can engineer quantum behavior on demand.

The less obvious implication is how this discovery stretches past physics departments and into the ecosystem of technology and information.

Fundamentally, this Nobel is about trying to order chaos and harness uncertainty to generate measurable and repeatable results – the bread and butter of anyone involved with data models, predictive analytics or AI systems. Similar to quantum tunnelling, data science lives because of the tension between determinism and probability.

The experimentation rigor of Clarke, Devoret and Martinis, carefully isolating noise, quantifying randomness and turning statistical chaos into structured insight can be compared to the development of any robust machine learning system. Their success reminds us complexity is manageable provided we are aware of its probabilities.

The next quantum leap, be it in AI or finance or computation, will be initiated not by a formula, but by the desire to look at an insurmountable obstacle and say, ‘What if we tunnel through?’

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Further reading: Advanced information. NobelPrize.org. Nobel Prize Outreach 2025. Sat. 18 Oct 2025. https://www.nobelprize.org/prizes/physics/2025/advanced-information
 
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This year’s Nobel Prize in Physics is a masterclass in managing uncertainty. Quantum tunnelling now powers quantum computing and reshapes how we think about probability, prediction and precision.
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