On Tuesday, October 7, 2025, the Royal Swedish Academy of Sciences in Stockholm announced the recipients of the 2025 Nobel Prize in Physics: John Clarke, Michel H. Devoret, and John M. Martinis. The trio—a Briton, a Frenchman, and an American—were honored for their groundbreaking discovery of macroscopic quantum mechanical tunneling and energy quantization in an electrical circuit. Conducted in the 1980s at the University of California, Berkeley, their experiments demonstrated that the peculiar and counterintuitive phenomena of quantum mechanics, typically confined to the microscopic realm of atoms and subatomic particles, could be observed in a system large enough to be held in the hand. This achievement not only redefined the boundaries between the quantum and classical worlds but also laid the foundation for transformative technologies, including quantum computing and ultra-sensitive measurement devices.
The Nobel Prize in Physics, established by Alfred Nobel’s will in 1895, is one of the most prestigious awards in science, recognizing discoveries that have profoundly impacted our understanding of the universe. Since its inception in 1901, the prize has been awarded 119 times to 230 laureates, celebrating milestones from the discovery of X-rays to the detection of gravitational waves. The 2025 award to Clarke, Devoret, and Martinis underscores the enduring importance of quantum mechanics, a field that has revolutionized physics over the past century and continues to drive innovation in the 21st century. Their work, described by the Nobel Committee as making “the bizarre properties of the quantum world concrete in a system big enough to be held in the hand,” represents a pivotal moment in the history of physics, bridging fundamental science with practical applications.
Understanding Quantum Mechanics: A Primer
To appreciate the significance of the laureates’ discovery, it is essential to understand the principles of quantum mechanics, a branch of physics that governs the behavior of matter and energy at the smallest scales. Developed in the early 20th century through the work of pioneers like Max Planck, Albert Einstein, Niels Bohr, and Werner Heisenberg, quantum mechanics challenges our classical intuition about how the world works. Unlike classical physics, which describes the predictable motion of macroscopic objects like planets or pendulums, quantum mechanics reveals a probabilistic and often bizarre reality at the level of atoms and subatomic particles.
One of the hallmark phenomena of quantum mechanics is quantum tunneling, which allows a particle to pass through a barrier that, according to classical physics, it should not have the energy to surmount. To visualize this, imagine a ball rolling toward a hill. In the classical world, the ball would need enough kinetic energy to climb over the hill to reach the other side. If it lacks that energy, it would roll back. In the quantum world, however, the particle has a non-zero probability of “tunneling” through the barrier, appearing on the other side without ever crossing over it. This phenomenon is not just a theoretical curiosity; it underpins processes like nuclear fusion in stars, where protons tunnel through repulsive electrostatic barriers to fuse, releasing the energy that powers the sun.
Another key principle is energy quantization, which dictates that certain systems, such as electrons in an atom, can only occupy discrete energy levels rather than a continuous range. This concept explains why atoms emit or absorb light at specific wavelengths, leading to the development of technologies like lasers, semiconductors, and atomic clocks. For example, the electrons in an atom can only exist in specific orbits, each corresponding to a distinct energy level, much like the rungs of a ladder. Transitions between these levels result in the emission or absorption of photons, which form the basis of spectroscopy and many modern technologies.
Quantum mechanics, however, is typically observed at microscopic scales, where individual particles or small groups of particles exhibit these behaviors. In macroscopic systems—those involving large numbers of particles, such as everyday objects like tables, chairs, or electrical circuits—quantum effects tend to vanish. This disappearance is due to a phenomenon called decoherence, where interactions with the environment cause quantum behaviors to average out, leaving only classical physics to describe the system. For decades, scientists believed that quantum phenomena were inherently confined to the microscopic world, making it impossible to observe effects like tunneling or energy quantization in larger systems.
The Breakthrough: Quantum Effects in a Macroscopic Circuit
In the 1980s, John Clarke, Michel H. Devoret, and John M. Martinis shattered this assumption through a series of groundbreaking experiments conducted at the University of California, Berkeley. Working with superconducting electrical circuits known as Josephson junctions, they demonstrated that quantum tunneling and energy quantization could occur in a system that was macroscopic in scale—large enough to be seen with the naked eye or manipulated by hand. This discovery was a monumental leap, as it challenged the conventional wisdom that quantum mechanics was irrelevant to large systems and opened new possibilities for harnessing quantum effects in practical applications.
A Josephson junction is a device consisting of two superconductors separated by a thin insulating barrier, typically just a few nanometers thick. Superconductors are materials that, when cooled to extremely low temperatures (near absolute zero, or -273.15°C), conduct electricity with zero resistance due to the pairing of electrons into a collective quantum state. In a Josephson junction, a supercurrent—a current of paired electrons—can flow across the insulating barrier without resistance, a phenomenon predicted by British physicist Brian Josephson in 1962, for which he won the Nobel Prize in Physics in 1973.
The laureates’ experiments focused on the behavior of supercurrents in these junctions. They found that the current could “tunnel” through the insulating barrier in a manner consistent with quantum mechanics, rather than classical physics. In classical terms, the current would need sufficient energy to overcome the barrier, but in the quantum regime, the supercurrent could pass through it probabilistically, exhibiting quantum tunneling. Furthermore, the energy levels of the circuit itself were quantized, meaning the system could only exist in discrete energy states, much like an atom. This quantization was observed in the form of discrete voltage steps across the junction, a direct manifestation of quantum mechanics at a macroscopic scale.
What made these experiments extraordinary was the size of the system. Unlike previous studies of quantum phenomena, which involved individual particles or small atomic systems, the Josephson junctions used by Clarke, Devoret, and Martinis were macroscopic devices, measurable in millimeters or centimeters. To achieve this, the researchers had to carefully isolate the circuits from environmental noise—such as thermal fluctuations or electromagnetic interference—that could cause decoherence and suppress quantum effects. By maintaining the circuits at cryogenic temperatures and shielding them from external disturbances, they preserved the delicate quantum coherence necessary for tunneling and quantization to occur.
The Royal Swedish Academy of Sciences lauded the trio for demonstrating that “the bizarre properties of the quantum world can be made concrete in a system big enough to be held in the hand.” This achievement not only expanded the theoretical understanding of quantum mechanics but also had profound implications for technology, as it showed that quantum effects could be engineered and controlled in practical systems.
The Laureates: A Collaborative Triumph
The 2025 Nobel Prize recognizes the collaborative efforts of three exceptional physicists, each bringing unique expertise to the discovery.
John Clarke, a British physicist, has spent much of his career advancing the field of superconductivity and its applications. Born in the United Kingdom, Clarke earned his Ph.D. from the University of Cambridge before joining the faculty at UC Berkeley. His research focused on superconducting devices, particularly superconducting quantum interference devices (SQUIDs), which are among the most sensitive magnetometers known to science. Clarke’s expertise in low-temperature physics and precision measurement was critical to the design and execution of the experiments that demonstrated macroscopic quantum effects. His contributions extended beyond the laboratory, as he trained generations of physicists and fostered interdisciplinary collaborations in condensed matter physics.
Michel H. Devoret, a French physicist, is a leading figure in quantum electronics and quantum coherence. After earning his Ph.D. from the University of Paris-Sud, Devoret conducted postdoctoral research at UC Berkeley, where he collaborated with Clarke and Martinis. His work combines theoretical insights with experimental innovation, particularly in the study of superconducting circuits and their quantum properties. Devoret’s contributions to the field of quantum information science have been instrumental in advancing our understanding of how quantum coherence can be maintained in complex systems. Now a professor at Yale University, he continues to explore the frontiers of quantum mechanics and its applications in computing and sensing.
John M. Martinis, an American physicist, is renowned for his contributions to quantum computing and superconducting circuits. After completing his Ph.D. at UC Berkeley, Martinis remained at the institution as a researcher, where he played a key role in the Nobel Prize-winning experiments. In subsequent years, he joined the University of California, Santa Barbara, and later led Google’s quantum computing efforts, where he advanced the development of superconducting qubits—quantum bits that form the basis of quantum computers. Martinis’ work has bridged fundamental research and practical applications, making him a pivotal figure in the global race to build scalable quantum computers.
Together, the trio’s collaboration at Berkeley in the 1980s marked a turning point in quantum physics. Their complementary skills—Clarke’s expertise in superconductivity, Devoret’s theoretical and experimental insights, and Martinis’ focus on scalable quantum systems—enabled them to achieve what was once thought impossible: observing quantum phenomena in a macroscopic system.
Implications for Science and Technology
The discovery of macroscopic quantum mechanical tunneling and energy quantization has had a transformative impact on both fundamental science and applied technology. By demonstrating that quantum effects could persist in larger systems, the laureates opened new avenues for research and innovation, with implications that continue to unfold decades later.
Superconducting Quantum Interference Devices (SQUIDs)
One of the most immediate applications of the laureates’ work was the development of superconducting quantum interference devices (SQUIDs). These devices, which rely on the quantum properties of Josephson junctions, are capable of detecting extremely weak magnetic fields with unprecedented sensitivity. SQUIDs operate by measuring changes in the magnetic flux through a superconducting loop containing one or more Josephson junctions. The quantum tunneling of supercurrents in these junctions allows SQUIDs to detect magnetic fields as small as a billionth of the Earth’s magnetic field.
SQUIDs have found applications in a wide range of fields. In medical imaging, they are used in magnetoencephalography (MEG), a technique for mapping brain activity by detecting the magnetic fields produced by neuronal activity. This non-invasive method has advanced our understanding of neurological disorders and improved diagnostic capabilities. In geophysics, SQUIDs are employed to study the Earth’s magnetic field, aiding in mineral exploration and earthquake prediction. They are also used in fundamental physics experiments, such as searches for dark matter and tests of gravitational theories.
The development of SQUIDs would not have been possible without the foundational insights provided by Clarke, Devoret, and Martinis. Their demonstration of macroscopic quantum effects provided the theoretical and experimental framework for designing these ultra-sensitive devices, which continue to play a critical role in science and technology.
Quantum Computing
Perhaps the most far-reaching impact of the laureates’ discovery lies in the field of quantum computing, a revolutionary approach to computation that harnesses the principles of quantum mechanics. Unlike classical computers, which process information using bits that represent either 0 or 1, quantum computers use quantum bits, or qubits, which can exist in a superposition of 0 and 1 simultaneously. This property, along with quantum entanglement and tunneling, allows quantum computers to perform certain calculations—such as factoring large numbers or simulating complex quantum systems—exponentially faster than classical computers.
The laureates’ work on superconducting circuits provided a critical foundation for the development of superconducting qubits, one of the leading platforms for quantum computing. In a superconducting qubit, the quantum state is encoded in the collective behavior of billions of electrons in a Josephson junction, which behaves as a macroscopic quantum system. The ability to observe and control quantum tunneling and energy quantization in these circuits, as demonstrated by Clarke, Devoret, and Martinis, was a key step in realizing practical qubits.
John Martinis, in particular, has been a pioneer in this field. During his tenure at Google, he led efforts to build a quantum computer capable of achieving quantum supremacy—the point at which a quantum computer can perform a task infeasible for classical computers. In 2019, Google announced that its 53-qubit quantum processor, named Sycamore, had performed a specific calculation in 200 seconds, a task that would have taken the world’s fastest supercomputer thousands of years. While this milestone was a proof of concept rather than a practical application, it underscored the potential of superconducting qubits and the enduring impact of the laureates’ work.
Today, companies like Google, IBM, Rigetti Computing, and others are racing to build scalable quantum computers, with superconducting circuits playing a central role. These efforts promise to revolutionize fields such as cryptography, materials science, drug discovery, and artificial intelligence. For example, quantum computers could simulate the behavior of molecules at the quantum level, enabling the design of new pharmaceuticals or catalysts for clean energy. They could also break current encryption standards, necessitating the development of quantum-resistant cryptography.
Precision Measurement and Quantum Sensors
Beyond quantum computing, the laureates’ discovery has implications for precision measurement and quantum sensors. The ability to control quantum coherence in macroscopic systems has led to the development of devices that can measure physical quantities—such as magnetic fields, electric currents, or gravitational forces—with unprecedented accuracy. These devices have applications in fundamental physics, where they are used to test theories like general relativity, and in practical fields like navigation and medical diagnostics.
For example, quantum sensors based on superconducting circuits can detect minute changes in physical parameters, making them ideal for applications like GPS-free navigation or detecting gravitational anomalies. These sensors could also be used in space exploration to measure the properties of distant planets or in environmental monitoring to track changes in the Earth’s magnetic field.
Fundamental Physics
The laureates’ work has also inspired fundamental research into the nature of quantum mechanics and the boundary between the quantum and classical worlds. One of the enduring questions in physics is why quantum effects are not observed in everyday objects. The phenomenon of decoherence explains this transition, but the precise mechanisms remain an active area of study. By demonstrating quantum coherence in a macroscopic system, Clarke, Devoret, and Martinis provided a platform for exploring these questions experimentally.
Their experiments have also contributed to tests of quantum mechanics itself. For instance, researchers have used superconducting circuits to investigate the Schrödinger’s cat paradox, a thought experiment that illustrates the strangeness of quantum superposition. In the paradox, a cat in a box is simultaneously alive and dead until observed. Superconducting circuits, which can exist in superpositions of macroscopically distinct states, serve as real-world analogs of Schrödinger’s cat, allowing scientists to probe the limits of quantum mechanics.
The Nobel Prize in Physics: A Historical Perspective
The Nobel Prize in Physics has a storied history, recognizing transformative contributions to our understanding of the universe. Since 1901, the prize has been awarded 119 times to 230 laureates, with only one individual, John Bardeen, receiving it twice. Bardeen, a condensed matter physicist, won in 1956 for the invention of the transistor, which revolutionized electronics, and in 1972 for the theory of superconductivity, which explained the zero-resistance behavior of certain materials at low temperatures. The 2025 award to Clarke, Devoret, and Martinis continues the tradition of honoring advances in condensed matter physics, a field that has produced numerous Nobel Prizes due to its profound impact on both science and technology.
The Nobel Prize has celebrated a wide range of discoveries, from Wilhelm Röntgen’s discovery of X-rays in 1901 to the 2017 award for the detection of gravitational waves, confirming a prediction of Einstein’s general relativity. Other notable awards include the 1918 prize to Max Planck for quantum theory, the 1933 prize to Erwin Schrödinger and Paul Dirac for their contributions to quantum mechanics, and the 2001 prize for the discovery of Bose-Einstein condensates, a state of matter where quantum effects become macroscopic under extreme conditions.
In 2024, the Nobel Prize in Physics was awarded to John J. Hopfield and Geoffrey Hinton for their foundational discoveries in machine learning with artificial neural networks. Their work, which has driven the artificial intelligence revolution, highlights the Nobel Prize’s role in recognizing diverse fields that shape modern science and technology. The 2025 award, by contrast, returns to the realm of fundamental physics, celebrating a discovery that bridges the microscopic and macroscopic worlds.
The Broader Impact: Quantum Mechanics in the 21st Century
The discovery of macroscopic quantum mechanical tunneling and energy quantization has had a lasting impact on the trajectory of physics and technology. It has inspired new generations of scientists to explore the quantum world, pushing the boundaries of what is possible. The laureates’ work has also highlighted the importance of interdisciplinary collaboration, as their success relied on combining expertise in superconductivity, quantum mechanics, and experimental physics.
In the broader context, their discovery underscores the transformative potential of fundamental research. Quantum mechanics, once a purely theoretical field, has given rise to technologies that define the modern world, from transistors to MRI machines. The work of Clarke, Devoret, and Martinis builds on this legacy, paving the way for innovations that could reshape society in the comin
