One of the central goals of my research is to understand quantum systems from the standpoint of computational complexity. Physicists have been using computers for decades to understand various aspects of quantum systems, but these methods are typically heuristic and achieve success on only limited classes of systems. I study the properties of quantum systems and seek to understand which systems have inherent computational difficulty and which systems can be simulated efficiently on a classical or quantum computer.

Most of the research in the early part of my career was focused on online algorithms, in which the input to a problem arrives incrementally and decisions about the final output must be made before the full problem specification is known. I focused in particular on applications to computer systems, such as memory management, scheduling, and energy efficient computing.