It is once again Nobel Prize season, and this year’s top prize in physics honours three quantum physicists for their discovery of “macroscopic quantum mechanical tunnelling and energy quantization in an electric circuit.” 

The winners

The prize was awarded jointly to a team of three researchers for work they conducted in the mid-1980s. 

John Clarke of the University of California, Berkeley, Michel H. Devoret of Yale University, and John M. Martinis of the University of California, Santa Barbara will take home this year’s Nobel at the prize ceremony on December 10, 2025, in Stockholm, Sweden. 

It’s not unusual for the Nobel Committee to wait 40 years after the research was initially published to award the team. Last year, the committee awarded John J. Hopfield and U of T’s own Geoffrey Hinton for foundational discoveries that enabled the current rise of machine learning and artificial intelligence — work that was done by him in the mid to late ’80s. 

In this case, the committee is now recognizing the researchers for their pioneering work in quantum computing. The work is reflected in current quantum computing advancements, including those by Google, Microsoft, and IBM. 

The science

Quantum mechanics is generally concerned with unconventional behaviours on a tiny scale — that of a single particle in a subatomic world. 

Imagine throwing a tennis ball at a wall. You could assume pretty confidently that it would bounce back. But a single particle might pass through an equivalent barrier in the quantum world and appear on the other side through a phenomenon called quantum tunnelling. These effects seem to disappear when looking at large-scale systems in the real world. 

In a series of experiments performed from 1984–1985, Clarke, Devoret, and Martinis demonstrated quantum behaviours at a macroscopic level — that trillions of particles bonded together could exhibit quantum tunnelling in unison.

To do this, they built an electrical circuit consisting of two superconducting wires — meaning that they are able to conduct electricity without any resistance or loss of energy through heat. The wires were separated by a thin layer of insulating material, which doesn’t conduct current. 

Because there’s no current in the insulating layer, charge is trapped inside that layer, and the classical laws of physics say that voltage should also measure zero. Just as a tennis ball thrown at a wall doesn’t have enough energy to break through it, the charge doesn’t have enough energy to leave the insulating layer. 

However, the researchers observed the system holding a nonzero voltage, which would only be possible if charge is able to leave the insulating layer through quantum tunnelling. The experiment essentially demonstrated the ability of billions of particles to exhibit quantum tunnelling on a scale previously unseen. 

In quantum mechanics, subatomic particles gain or lose energy in discrete or distinct whole amounts instead of continuously. 

For instance, an electron is a negatively charged subatomic particle that is found in layers, called orbitals, around the nucleus, or core, of an atom. It remains in a certain orbital unless it gets a specific quantity — a quantum — of energy. The electron cannot leave its specific orbital unless it gains or loses that specific quantum of energy. 

In the laureates’ experiments, they observed that the system only absorbed light at certain frequencies, which corresponded to particular quanta of energy. Since the system only responded to these specific quanta, the experiment demonstrated that the macroscopic scale also utilizes discrete quantities of energy, consistent with behaviours on the subatomic scale.

So what?

During the announcement of the award, the Nobel Committee highlighted the role of quantum mechanics in the continued development of advanced technology, including cellphones, cameras, and fibre optic cables — used to transmit signals quickly. 

The trio’s discoveries helped lay the groundwork for the quantum bit, also called the qubit, a fundamental part of the quantum computer. Where classical computers store information in bits, single-digit ones or zeroes, a qubit’s quantum properties allow the bit to be both one and zero at once, or to entangle or link with other qubits, opening up a new world of possibilities for processing speeds and applications. 

Quantum computing, which could process information at speeds much faster than existing classical computers, represents one of the current races in technological advancement. Although quantum computing remains largely impractical because of its high error rates and infrastructure costs, true quantum computers have the power to accelerate research in artificial intelligence, drug discovery, and countless other applications.

Martinis and Devoret have both worked for Google Quantum AI, which, in 2019, under Martinis, announced that they had created the first quantum computer able to perform a calculation that would be impossible for a classical computer to achieve. Devoret currently serves as Chief Scientist of Quantum Hardware at Google. 

Following the announcement, Clarke took the opportunity to criticize the Trump administration’s wide-ranging cuts to research funding in the United States. Speaking to Agence France-Presse (AFP) News, Clarke argued that reductions to research budgets and the dismissal of scientists from federal agencies “will cripple much of United States science research,” including fundamental research into quantum physics and computing. All three laureates currently live and work in the US, although Clarke is originally from England, and Devoret from France. 

Ultimately, the Nobel committee’s decision to highlight the work of Clarke, Devoret, and Martinis is a reminder of the yet untapped potential of quantum computing and applications of quantum physics. It is also a testament to the value of fundamental research and the scientific community. Congratulations to the laureates!