John Clarke

University of California, Berkeley


Primary Section: 13, Physics
Membership Type: International Member (elected 2012)

Biosketch

John Clarke was born in Cambridge, England in 1942. He received his degrees from Cambridge University: his B.A in 1964, M.A. and Ph.D. in 1968 and Sc.D. in 2003. In 1968 he moved to the Physics Department at the University of California, Berkeley as a postdoctoral scholar, and joined the faculty there in 1969. He also became a Faculty Senior Scientist at Lawrence Berkeley National Laboratory. He retired in 2010 to become a Professor of the Graduate School, and remains active in research.  Clarke’s research has mostly involved the fundamental science and applications of superconductivity. In particular, he has developed SQUIDs—Superconducting Quantum Interference Devices—which are ultrasensitive detectors of magnetic flux. Applications include condensed matter physics, geophysics, astrophysics, cosmology, medical physics—notably ultralow frequency magnetic resonance imaging—and quantum information. Clarke has had the privilege of advising over 100 graduate students and postdoctoral scholars, with whom he has published nearly 500 papers.  

Research Interests

Quantum Information: With Irfan Siddiqi, UC Berkeley. My main focus is on superconducting qubits based on Josephson junctions. I study limitations to the relaxation and decoherence times imposed by 1/f flux noise. Although it is generally accepted that the noise is generated by the reversal of spins on the surface of the superconductor, details of the mechanism and techniques to reduce the noise remain obscure.  Ultralow Field Magnetic Resonance Imaging: With Ben Inglis, UC Berkeley and Hui Dong, Shanghai. We are involved in several research topics, including imaging of the human brain, study of stroke in rat brains with potential application to the determination of the elapsed time since stroke in humans. and a detailed study of the relaxation and decoherence times in large molecules.   Searching for Axion Dark Matter: With the Axion Collaboration, based at the University of Washington, Seattle. The axion is a highly motivated candidate for the cold dark matter that comprises 85% of the mass of the Universe.  I have worked in this collaboration for 25 years since developing the high-frequency SQUID amplifier that enabled the use of the axion haloscope, a microwave cavity in a high magnetic field, to search for axions.

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