Mark Friesen is a condensed matter theorist, working mainly on problems related to quantum computing. A primary focus of his work involves the physics and operation of spin and charge qubits formed in semiconductor quantum dots. Research topics include the relation between semiconductor band structure and qubit operation, detrimental noise and noise mitigation in quantum devices, and simulations of realistic devices and the many-body qubit wave functions contained in them. All of these projects are closely aligned with ongoing experiments at UW-Madison and across the globe. A recent exciting direction involves topological qubits formed in germanium hole wires in contact with a superconductor. Friesen holds 6 patents and has authored or coauthored 129 peer-reviewed publications, with an h-factor of 46.