Our research is in the areas of quantum information and quantum optics. In quantum information, we are performing research into the most efficient ways of simulating physical quantum systems on a quantum computer. Such simulations are a very promising application for quantum computers, because simulating quantum systems is extremely important in areas such as design of molecules, and it is natural for quantum computers to give exponential speedups. Our research has shown how to perform simulations far more efficiently than the traditional product formula approach, and we are now researching the specific application of these techniques to quantum chemistry.
In the area of quantum optics, we are researching the most accurate ways to perform phase measurements. Phase measurements are needed for precision measurement, for example in gravitational wave detection. While coherent states as produced by a laser give one level of precision, special nonclassical states such as squeezed states or “NOON” states can potentially give much higher precision. Our research shows how to best perform measurements optimised for loss, how to resolve ambiguities in phase measurements arising from use of nonclassical states, and how to best use nonclassical states for tracking of a varying phase.
D. W. Berry, A. M. Childs, R. Cleve, R. Kothari, and R. D. Somma, Simulating Hamiltonian dynamics with a truncated Taylor series , Physical Review Letters 114, 090502 (2015)
D. W. Berry, A. M. Childs, R. Cleve, R. Kothari, and R. D. Somma, Exponential improvement in precision for simulating sparse Hamiltonians, In Proceedings of the 46th Annual ACM Symposium on Theory of Computing, pages 283-292 (2014)
D. W. Berry, M. J. W. Hall, and H. M. Wiseman, Stochastic Heisenberg Limit: Optimal Estimation of a Fluctuating Phase, Physical Review Letters 111, 113601 (2013)
H. Yonezawa, D. Nakane, T. A. Wheatley, K. Iwasawa, S. Takeda, H. Arao, K. Ohki, K. Tsumura, D. W. Berry, T. C. Ralph, H. M. Wiseman, E. H. Huntington, and A. Furusawa, Quantum-enhanced optical-phase tracking, Science 337, 1514 (2012)
G. Y. Xiang, B. L. Higgins, D. W. Berry, H. M. Wiseman, and G. J. Pryde, Entanglement-enhanced measurement of a completely unknown phase, Nature Photonics 5, 43 (2011)
D. W. Berry and A. I. Lvovsky, Linear-Optical Processing Cannot Increase Photon Efficiency, Physical Review Letters 105, 203601 (2010)
Scientific Reports 4, 6955 (2014) DOI:http://dx.doi.org/10.1038/srep06955