John Clarke Awarded 2025 Nobel Prize in Physics
John Clarke, a former scientist at Berkeley Lab, has been awarded a share of the 2025 Nobel Prize in Physics. The recognition is for his work on quantum tunneling within an electric chip. He shares the prize with co-laureates Michel Devoret and John Martinis.
Research on Quantum Tunneling
The research, conducted at Berkeley Lab in the 1980s, investigated whether quantum mechanical principles could apply to systems larger than atoms. Supported by the Department of Energy's Office of Science, their experiments demonstrated that quantum behavior could persist in such systems. This work led to the discovery of macroscopic quantum tunneling and energy quantization in electrical circuits, earning the researchers the 2025 Nobel Prize.
Clarke was a scientist at Lawrence Berkeley National Laboratory and a professor of physics at the University of California, Berkeley, during the time of the prize-winning research. He retired from Berkeley Lab in 2010.
Prior Work on Superconductors and SQUIDs
Prior to the Nobel-recognized studies, Clarke conducted research on superconductors. In the late 1960s, scientists developed the superconducting quantum interference device (SQUID), an instrument used for detecting small magnetic fields. After joining Berkeley Lab in 1969, Clarke contributed to the refinement and expansion of SQUID applications.
SQUIDs have been utilized across various disciplines, including:
- Geophysics, for mapping mineral deposits.
- Materials science.
- Particle physics, in the search for dark matter.
- Neuroscience, for imaging brain activity.
Clarke's group also developed high-temperature SQUID technology, which broadened their operational environments beyond specialized cryogenic settings. This research received support from the DOE’s Basic Energy Sciences program over several decades.
Development of Superconducting Circuits
In the mid-1980s, Clarke’s group focused on the Josephson junction, a SQUID component that facilitates electron tunneling through an insulating barrier between two superconductors. Clarke, Devoret, and Martinis designed a superconducting circuit that could be cooled and controlled. Measurements of current flow in this circuit indicated behavior consistent with a single quantum particle, despite the circuit's atomic composition. The circuit exhibited discrete energy levels and quantum tunneling through an energy barrier, aligning with quantum mechanics predictions.
The 1984-85 experiments demonstrated macroscopic quantum tunneling and energy quantization in a manufactured object. The Josephson circuits from these experiments served as precursors to modern superconducting qubits, which are foundational components of many quantum computers. Clarke's subsequent research contributed to methods for measuring and controlling these quantum systems while minimizing noise.
Beyond quantum computing, Clarke's SQUID research influenced experimental techniques. Derivatives of his devices are currently employed for detecting magnetic signals from biological systems, analyzing geological samples, and searching for dark matter particles.
DOE Support and Future Quantum Research
The DOE’s Basic Energy Sciences program supported the fundamental studies of superconductivity and quantum materials conducted by Clarke and his collaborators. This long-term investment facilitated discoveries that inform current technologies.
Following the 1985 findings, DOE-supported investigations have advanced the field. A DOE Basic Energy Sciences Advisory Committee report identified these efforts as a basis for current quantum computing approaches, which often involve the same superconducting circuits and quantum effects initially observed by Clarke, Devoret, and Martinis.
Clarke’s experiments demonstrated the application of quantum effects at larger scales. This contributed to the development of what is known as the "second quantum revolution," characterized by the deliberate application of quantum effects for sensing, communication, and computation.
Berkeley Lab continues to advance quantum computing through its participation in the National Quantum Information Science (QIS) Research Centers, including the Berkeley Lab-led Quantum Systems Accelerator. The lab collaborates with industry and academia to fabricate and test quantum devices, develop software and algorithms, and construct prototype quantum computers and networks.
Lawrence Berkeley National Laboratory (Berkeley Lab) is a national laboratory managed by the University of California for the U.S. Department of Energy’s Office of Science. Founded in 1931, the lab has been associated with 17 Nobel Prizes.
DOE’s Office of Science supports basic research in the physical sciences in the United States.