2021 Nevill Mott Medal and Prize
Professor Richard J Warburton for pioneering work in semiconductor quantum dots and solid-state quantum optics, especially the invention and application of Coulomb blockade devices to create coherent spin-photon interfaces and quantum light sources.
One of Professor Richard J Warburton’s most significant achievements and contributions to science is pioneering the design, fundamental characterisation and exploitation of Coulomb blockade devices with optically active quantum dots.
His seminal 2000 report presented the first design and spectroscopy of a heterostructure device to enable Coulomb blockade: loading single electrons or holes one-by-one into a single quantum dot. Over the following two decades, Warburton has consistently been at the forefront of the field.
He has provided an in-depth fundamental understanding and techniques to engineer the particle interactions in single quantum dots. Warburton has made fundamental breakthroughs in our understanding of spin coherence and dephasing in semiconductors. He has also applied techniques from atom optics and nuclear magnetic resonance spectroscopy to coherently manipulate the light-matter interface for control of single spins in semiconductors.
Another significant achievement over the last two decades has been improving the purity and optical quality of III-V semiconductor materials. Via close collaborations and with constant feedback and sample iterations with growers, Warburton has pushed material quality to its utmost purity, reducing noise levels to their intrinsic limits.
To do this, Warburton has invented techniques to characterise noise sources in semiconductors and identified metrics to provide molecular-beam epitaxy growers with these insights.
Warburton has regularly invented new experimental designs that then permeate the field of low-temperature physics and optics. Three examples stand out. Warburton co-designed with Professor Khaled Karrai low-temperature microscope inserts and optics that went on to become the foundation of the spin-out attocube, now the world leader in cryogenic nanopositioners and low-vibration closed-cycle cryostats.
He also developed the dark-field confocal microscope used for resonance fluorescence that has been copied by many labs around the world. Finally, in 2019 Warburton reported a stunning advance in cavity quantum electrodynamics (cavity-QED) via a breakthrough in the design of an open-access, fully tuneable cavity.
While this provided access to regimes of cavity-QED never before probed experimentally, perhaps the most remarkable aspect was the engineering of the cavity and sample themselves. This was an exercise in persistence, perfection and insight.
While many groups around the world working in atom optics and solid-state optics pursued various types of optical cavities and achieved steady advances, Warburton persisted with a design discarded by many, steadily improving cavity stability and quality over the years in parallel to sample quality. This allowed him to demonstrate the world’s brightest source of on-demand single photons in 2021.