Gullans's research interests center on the theoretical study of quantum information systems and quantum simulators in nonperturbative and strongly-interacting limits. His current efforts are focused on the physics of error correction and fault-tolerance in near-term devices and scalable tomography of quantum simulators.

A common theme in this research is understanding the role of randomness, noise and disorder in many-body quantum dynamics using the theoretical methods of statistical physics. The long term goal of the research is to develop quantum simulators into reliable, computational tools for the study of many-body quantum physics and complex systems.