In 1991 he was elected a junior research fellow and subsequently a research fellow at Merton College, Oxford. At the time he established the first research group in quantum cryptography and computation, based in the Clarendon Laboratory, Oxford. Subsequently, it evolved into the Centre for Quantum Computation, now based at DAMTP in Cambridge. Between 1993 and 2000 he held a position of the Royal Society Howe Fellow. In 1998 he was appointed a professor of physics at the University of Oxford and a fellow and tutor in physics at Keble College, Oxford. From 2002 until early 2007 he was the Leigh-Trapnell Professor of Quantum Physics at the Department of Applied Mathematics and Theoretical Physics, Cambridge University and a professorial fellow of King's College, Cambridge. Since 2007 he has been a professor of quantum physics at the Mathematical Institute, University of Oxford, and a Lee Kong Chian Centennial Professor at the National University of Singapore. He has worked with and advised several companies and government agencies. He has served on several professional advisory boards and is one the trustees of The Croucher Foundation.
Research
Ekert's research extends over most aspects of information processing in quantum-mechanical systems, with a focus on quantum cryptography and quantum computation. Expanding on an early proposal of David Deutsch for using quantum non-locality and Bell's inequalities to achieve secure key distribution he analysed entanglement-based quantum key distribution in more detail in his 1991 paper which generated a spate of new research that established a vigorously active new area of physics and cryptography. It is one of the most cited papers in the field and was chosen by the editors of the Physical Review Letters as one of their "milestone letters", i.e. papers that made important contributions to physics, announced significant discoveries, or started new areas of research. His subsequent work with John Rarity and Paul Tapster, from the Defence Research Agency in Malvern, resulted in the proof-of-principle experimental quantum key distribution, introducing parametric down-conversion, phase encoding and quantum interferometry into the repertoire of cryptography. He and collaborators were the first to develop the concept of a security proof based on entanglement purification. Ekert and colleagues have made a number of contributions to both theoretical aspects of quantum computation and proposals for its experimental realisations. These include proving that almost any quantum logic gate operating on two quantum bits is universal, proposing one of the first realistic implementations of quantum computation, e.g. using the induced dipole-dipole coupling in an optically driven array of quantum dots, introducing more stable geometric quantum logic gates, and proposing "noiseless encoding", which became later known as decoherence free subspaces. His other notable contributions include work on quantum state swapping, optimal quantum state estimation and quantum state transfer. With some of the same collaborators, he has written on connections between the notion of mathematical proofs and the laws of physics. He has also contributed semi-popular writing on the history of science.
