Assistant Professor Rahul Jain announced in August 2009 a breakthrough paper in which he showed that quantum interactive proof systems provide no more computational power than classical ones, and thus QIP = PSPACE = IP. This solves a long standing open problem in the theory of quantum computation. Dr Jain is with the Department of Computer Science in NUS School of Computing, and he holds a joint appointment at the Centre of Quantum Technologies. More details of his work may be found here