Three American physicists received the 2025 Nobel Prize in Physics for a series of experiments in the 1980s that successfully demonstrated the strange rules of quantum mechanics on a scale large enough to be held. John Clarke, Michel H. Devoret, and John M. Martinis were honored for proving that engineered electrical circuits, when cooled to near absolute zero, could exhibit quantum behaviors previously thought to be confined to the microscopic realm of single atoms and particles.
Their groundbreaking work established the foundation for building the quantum machines that are central to modern research in the field. By creating what are effectively large, “artificial atoms” from superconducting materials, they showed it was possible to control and observe quantum phenomena like tunneling and discrete energy levels in a tangible system. This fundamental breakthrough directly enabled the development of the superconducting qubits that are the core processing units in today’s most powerful prototype quantum computers, transforming a theoretical curiosity into a practical technology.
The Laureates and a Shared History
The prize recognizes a collaboration that began at the University of California, Berkeley, during 1984 and 1985. John Clarke, now a professor of physics at the university, led the research group. The team included his doctoral student at the time, John M. Martinis, and a postdoctoral researcher, Michel H. Devoret. Martinis is now a professor of physics at the University of California, Santa Barbara, and previously led the quantum hardware division at Google’s Quantum AI lab. Devoret serves as a professor of applied physics at Yale University. Their combined efforts at Berkeley produced the foundational experiments cited by the Royal Swedish Academy of Sciences.
Observing the Quantum World at Scale
The central achievement of the laureates was demonstrating two distinctly quantum effects—macroscopic tunneling and energy quantization—in an engineered electrical circuit. Quantum mechanics predicts that particles can “tunnel” through an energy barrier that they classically should not be able to overcome. While this was understood for subatomic particles, the team showed that a collective system involving billions of electrons could perform the same feat. Their device behaved as a single entity, governed by a unified wave function, and could tunnel from one state to another as if passing through a solid wall.
Furthermore, their experiments confirmed that the energy of this macroscopic system was quantized, meaning it could only absorb or emit energy in discrete packets, or quanta. By exposing their circuit to microwaves, they observed that it jumped between distinct energy levels, much like a natural atom. This provided concrete evidence that the principles of quantum mechanics could be engineered and observed in a human-made object, bridging the gap between the bizarre microscopic world and the tangible macroscopic one.
From Experiment to Foundational Technology
The work of Clarke, Devoret, and Martinis effectively provided the blueprint for the superconducting qubit, the workhorse of modern quantum computing. A qubit, or quantum bit, is the basic unit of quantum information. While a classical bit is either a 0 or a 1, a qubit can exist in a superposition of both states simultaneously. The artificial atoms created by the laureates, with their distinct low-energy states, provided a perfect physical system to represent the 0 and 1 of a qubit.
Their findings, though conducted decades ago, laid the essential groundwork for the massive global effort to build powerful quantum computers. Companies like Google and IBM now rely on designs that are direct descendants of the laureates’ early circuits. Göran Johansson, a member of the Nobel Committee for Physics, stated that the discovery “paved the way to model quantum physics on electric chips, create artificial atoms and lay the groundwork for continued research into the construction of ultra powerful problem-solving quantum computers.”
The Josephson Junction’s Critical Role
The key component that enabled this breakthrough was the Josephson junction, a device named after physicist Brian Josephson, himself a Nobel laureate. A Josephson junction consists of two superconducting materials separated by a very thin insulating barrier. In the laureates’ experiments, this junction was integrated into a superconducting loop. This specific architecture is what allowed the entire circuit, with its billions of electrons, to behave as a single coherent quantum object. The junction facilitated the quantum tunneling effect, allowing the collective state of the electrons to pass through the insulating barrier in a measurable way. It was the precise control and construction of this device that made the observation of macroscopic quantum phenomena possible.
Implications for a Quantum Future
The impact of demonstrating quantum mechanics in electrical circuits extends far beyond building computers. These artificial atoms are now used as tools to simulate other complex quantum systems, helping scientists understand phenomena in materials science and chemistry that are impossible to model with classical supercomputers. The ability to engineer and control quantum states with precision opens the door to developing ultra-sensitive detectors, new types of sensors, and potentially novel materials.
The award affirms the long path from fundamental scientific discovery to revolutionary technology. By bringing the esoteric rules of the quantum world into the domain of electrical engineering, the laureates provided a vital spark. As Nobel committee chair Olle Eriksson noted, “It is wonderful to be able to celebrate the way that century-old quantum mechanics continually offers new surprises.” The work of Clarke, Devoret, and Martinis ensures that these surprises will continue to shape the future of technology for decades to come.
