Title: Noise, Decoherence, and Parameter Shifts in Silicon-based Qubit Devices

Speaker: Robert Joynt, University of Wisconsin-Madison

Time: 2026-03-23 16:00

Venue: Room W105, Physics Building

Abstract:Electric field noise is a source of several harmful effects in quantum-dot quantum computers. I will start with a general introduction to this noise, whose sources are not well understood. I will describe some theoretical tools based on Bayesian inference that we have developed in order to deduce the physical nature of the sources from experimental data. The most important consequence of the noise is decoherence, but I will argue that it also causes the qubit frequencies to drift. This is also an issue for the smooth operation of a quantum computer.

Bio：Robert Joynt received his Ph.D. from the University of Maryland in 1982 and was a postdoctoral fellow at the Cavendish Laboratory of the University of Cambridge and the Institute for Theoretical Physics at ETH-Zurich. From 1986-2023 he was Professor of Physics at the University of Wisconsin-Madison, where he also served as Department Chair.  His research in condensed matter physics has ranged from the quantum Hall effect to high-Tc superconductivity to superfluidity in neutron stars. In quantum computing, active areas include semiconductor qubits, quantum correlations, and error correction schemes for neutral atom systems. At present he is researching ways to speed up the quantum optimization algorithms, decoherence from evanescent-wave Johnson noise, and new designs for qubit devices.