The 2025 Nobel Prize in Physics honors John Clarke, Michel Devoret, and John Martinis for their groundbreaking mid-1980s experiments demonstrating macroscopic quantum phenomena in superconducting circuits, fundamentally reshaping our understanding of quantum mechanics and laying the bedrock for advanced quantum technologies from powerful computers to ultra-sensitive sensors.
The Royal Swedish Academy of Sciences announced on October 7, 2025, that the Nobel Prize in Physics for 2025 has been awarded to three distinguished US-based scientists: John Clarke, Michel H. Devoret, and John M. Martinis. Their pioneering work, conducted in the mid-1980s, demonstrated that the enigmatic properties of quantum mechanics—traditionally thought to apply only to the subatomic realm—could be made concrete and observable on a much larger, macroscopic scale. This revelation has profoundly impacted our understanding of physics and opened vast opportunities for developing the next generation of quantum technology.
Olle Eriksson, chair of the Nobel Committee for Physics, lauded the laureates’ discoveries, stating, “It is wonderful to be able to celebrate the way that century-old quantum mechanics continually offers new surprises. It is also enormously useful, as quantum mechanics is the foundation of all digital technology.” Indeed, the committee highlighted that their experiments revealed “quantum physics in action,” providing measurable proof and a deeper understanding of phenomena crucial for modern advancements.
Bringing Quantum Mechanics to the Visible World
For decades, the bizarre, indeterminate, and inherently uncertain wave-like behaviors of quantum mechanics were largely confined to tiny, microscopic, even subatomic scales. Our classical world dictates that a ball thrown against a wall will always bounce back, never passing through. But in the quantum realm, a particle can exhibit quantum tunneling—a non-zero probability of passing through a barrier it classically shouldn’t have enough energy to overcome.
The core challenge was observing these effects not with individual electrons, but with systems large enough to see with the naked eye. This is where the work of Clarke, Devoret, and Martinis shone brightest. Their experiments in the mid-1980s centered around an electronic circuit built of superconductors. They conclusively demonstrated that quantum mechanical properties, such as tunneling and energy quantization, could manifest on a much larger, macroscopic scale.
Superconductors, materials that conduct electric current with no resistance at extremely low temperatures, were key to their success. The team leveraged a setup known as a Josephson junction, pioneered by Nobel laureate Brian Josephson in 1962. By separating two superconductors with a thin insulating layer, Clarke’s team created a system that behaved like a single quantum particle, effectively filling the entire circuit. As Steven Girvin, a physicist at Yale University, explains, their work showed “quantum mechanics all the way up.”
The Macroscopic Quantum Tunneling Breakthrough
The Berkeley group went to extraordinary lengths to isolate their system, cooling their centimeter-sized chip down to an astonishing 0.01 Kelvin (just one-hundredth of a degree above absolute zero). This meticulous isolation allowed them to drive a current and measure voltage in the circuit, repeatedly observing that electrons passed through the insulating barrier even when thermal noise was effectively eliminated. This provided conclusive proof of macroscopic quantum tunneling.
This phenomenon allows the system to spontaneously transition from a zero-voltage state to a “voltage-on” state without the classical input of energy needed to overcome a barrier. As Amir Caldeira, a theoretical physicist whose work with Tony Leggett helped inspire the experimental search, noted, this discovery demonstrated “a superposition of the ‘cat’ — dead or alive.” While Erwin Schrödinger’s famous thought experiment was meant to critique quantum paradoxes in the classical world, Clarke, Devoret, and Martinis showed that even macroscopic reality can indeed be “blurred” if sufficiently shielded from environmental noise, as described in a translation by physicist John D. Trimmer.
Quantized Energy Levels in Macroscopic Systems
Beyond tunneling, the Berkeley group made a second critical discovery: their superconducting circuit emitted and absorbed energy in discrete, quantized chunks—a hallmark of quantum systems. By shining microwaves at specific frequencies onto the circuit, they found it would only respond by absorbing or emitting energy in precise, distinct amounts, much like individual atoms. This demonstrated that an enormous macroscopic system, composed of quintillions of particles, could collectively behave as a single quantum system with quantized energy levels.
This was a remarkable advance, showing that the foundational principles of quantum mechanics extend far beyond the subatomic. While other quantum effects like lasers, superconductors, and superfluids had been observed on macroscopic scales, this was the first time vast numbers of particles were demonstrated to act cohesively as a single, controllable quantum entity.
Fueling the Next Generation of Quantum Technology
The implications of these mid-1980s breakthroughs are vast and continue to reshape modern technology. The Royal Swedish Academy of Sciences emphasized that the prize “has provided opportunities for developing the next generation of quantum technology, including quantum cryptography, quantum computers, and quantum sensors.”
Quantum Computing: The Grandfather of Qubits
Perhaps the most transformative impact has been on quantum computing. John Martinis, who later headed Google’s quantum artificial intelligence lab, was instrumental in applying these discoveries. The two lowest-energy states of these artificial, macroscopic atoms could be used as a solid-state qubit. According to Irfan Siddiqi, chair of UC Berkeley’s physics department, “This was the grandfather of qubits. Modern qubit circuits have more knobs and wires and things, but that’s just how to tune the levels, how to couple or entangle them. The basic idea that Josephson circuits could be quantized and were quantum was really shown in this experiment.”
Superconducting qubit circuits are now the foundation for many of the highest-performance quantum computers in existence, utilized by giants like Google and IBM. While the field has seen a “frenzy of research activity” and some “overstated claims” about quantum computing’s immediate capabilities, its foundational principles rest firmly on the work recognized by this Nobel Prize.
Beyond Computing: Broadening Quantum Applications
The laureates’ work extends far beyond quantum computers:
- Quantum Sensors: The circuits’ extreme sensitivity makes them ideal for detecting subtle phenomena. They are used in ultra-low-field MRI machines and enable ultra-precise measurements across various scientific disciplines, including neuroscience, geophysics, and meteorology.
- Dark Matter Search: These advanced circuits have been incorporated into the ongoing search for hypothetical dark matter particles called axions, demonstrating the unexpected reach of fundamental research into cosmic mysteries.
- Digital Technology Foundation: Even everyday technologies, from cell phones to computer microchips with their ubiquitous transistors, owe their underlying functionality to the principles of quantum mechanics, a field celebrating its 100th anniversary in 2025. This historical context is well-articulated by Scientific American, highlighting the enduring relevance of quantum physics.
The 2025 Nobel Prize in Physics not only celebrates a profound scientific achievement but also underscores the long-term, transformative power of fundamental research. John Clarke, Michel Devoret, and John Martinis have shown that the quantum world is not just a microscopic curiosity but a tangible, macroscopic reality, providing the bedrock for a future increasingly shaped by quantum ingenuity.
