Research
Theoretical physics and computational neuroscience: quantum error correction and collective photon emission on one side, and how complex, coordinated behavior emerges from simple inputs to a neural circuit on the other. The common thread is mathematical models of systems with many interacting parts.
Quantum error correction and fault tolerance
Roadmaps for large quantum computers often rest on the threshold theorem: as long as you keep the error rate per qubit below a certain value, error correction can hold errors in check. My doctoral research examined what happens when errors are not independent, which is harder to analyze but more realistic. These correlated errors can be negligible in a small system yet determine the fate of a large one — the collective emission rate grows with the number of qubits while the error-correction cycle runs at a fixed speed, so past some size the decay inevitably outruns the correction. This sets a ceiling that may or may not sit beyond any practical computation, and whether or not it does is one of the central questions that logical-qubit and error-correction claims turn on.
Collective emission in atomic ensembles
When many atoms couple to the same light field, they radiate together and emission can be sharply accelerated (superradiance) or suppressed (subradiance). I calculated the timescales and error rates of both in dilute atomic clouds, and with Klaus Mølmer at Aarhus derived the radiation eigenmodes of Dicke superradiance — the natural modes through which a large ensemble sheds its energy. This is a concrete realization of the physics underneath the fault-tolerance results that formed the basis of my graduate thesis.
Computational models of neural circuits
How does a simple command from the brain, carrying information only about direction and speed, transform into the precisely timed firing of thousands of individual neurons that is needed for coordinated locomotion? At the University of Oregon I modeled these spinal circuits, building recurrent neural network models with the connectivity of real cell types and tuning them until they reproduced what is recorded in a locomoting animal. Our work focused on a gear-shift mechanism, in which different circuits are engaged at different speeds.
The measurement problem
I consider the measurement problem one of the most important open problems in physics. If correlated decay places a practical ceiling on how large an entangled state can be sustained in an engineered system, as my doctoral work suggests, then perhaps a more fundamental mechanism prevents such large entangled states from ever forming or persisting over time. If true, this could have profound implications for the foundations of quantum mechanics and the notion of a universal wave function. I like to read and work on this problem whenever I can.
- Browne Award, UW–Madison Physics — awarded annually to one graduate student for outstanding accomplishments in research
- Dillinger Award for Teaching Excellence, UW–Madison Physics
- Teaching Fellow Award, College of Letters & Science — departmental nominee
- Van Vleck Fellowship for physics graduate students
- Invited speaker, Quantum Information Seminar, Ohio State University (2019)
- Phi Beta Kappa, Oberlin College