He is an editor of the journal Theory of Computing[3] and former editor for the journal Quantum Information & Computation.[4] His research interests include quantum information and quantum computation. He is well known for his work on quantum interactive proofs, and the quantum analogue of the celebrated result IP equals PSPACE, QIP equals PSPACE.[5][6][7] This was preceded by a series of results, showing QIP can be constrained to 3 messages,[8] QIP is contained in EXP,[9] and the 2-message version of QIP is in PSPACE.[10] He has also published important papers on quantum finite automata[11] and quantum cellular automata.[12] With Scott Aaronson, he showed that certain forms of time travel can make quantum and classical computation equivalent: together, the authors showed that quantum effects do not offer advantages for computation if computers can send information to the past through a type of closed timelike curve proposed by the physicist David Deutsch.[13]