I am a theorist working on problems in quantum optics and condensed matter physics. Our research projects deal with the interaction of light with matter: that is, how stuff with no mass interacts with stuff with mass.

Some of the work is focused on nonlinear quantum optical effects in integrated photonic devices, such as waveguides coupled to resonator structures. Understanding the generation and behavior of nonclassical light is central to developing schemes for optical implementation of quantum information processing and computing. I continue to collaborate with former graduate students and others at Xanadu (https://www.xanadu.ai), where I am a technical advisor, on the physics of “nonclassical light on a chip.”

Other research includes the theory of quantum interference effects in solids, where different optical processes (such as one-photon absorption and two-photon absorption) can interfere so that electrical currents, spin populations, and spin currents can be optically injected. Carriers can be optically placed in localized regions of reciprocal space and, with the advent of time-resolved ARPES (angle resolved photoemission spectroscopy) experimentalists should be able to use these initially localized distributions to study relaxation via the interaction of quasi-particles in conditions far removed from equilibrium. We want to be able to predict and explain such behavior.

We also want to understand the microscopic underpinnings of macroscopic concepts such as magnetization and polarization, extending the “modern theory of polarization and magnetism” into the optical domain via the introduction of microscopic magnetization and polarization fields. Unsurprisingly, we find that both the spectral and topological properties of the electronic band structure of a solid are central in understanding how these fields behave. The framework we are developing is well-suited to describe both the linear and nonlinear aspects of material response, from the THz to the x-ray.

All of these projects can be characterized as research at boundaries between our different viewpoints in physics: the boundary between classical and quantum, between equilibrium and nonequilibrium, and between macroscopic and microsopic. This is the kind of work that I find most interesting. You can check our most recent publications by googling “Sipe, J.E. – Google Scholar Citations,” and clicking on the entry it generates. Then click on “Year” to see the most recent publications listed first.

I can be reached at: sipe at physics dot utoronto dot ca.

Prof. John E. Sipe
J.E. Sipe
Department of Physics
University of Toronto