My research is in the areas of quantum information and quantum optics. In quantum information, I developed the most efficient known algorithms for simulation of physical systems, which has been used as the basis for important new quantum algorithms. In the area of quantum optics, I invented the most accurate known methods to measure optical phase by using adaptive techniques, and am actively collaborating with experimental groups for demonstration of these methods.
My CV is available here.
- 6/06/2013: We have discovered a new form of the Heisenberg limit that applies for a stochastic phase. This stochastic Heisenberg limit holds for any signal with a correlation spectrum that asymptotically follow a power law. In the limit where the high frequency variation is suppressed, the usual Heisenberg limit is recovered. For Wiener noise we obtain the same scaling as can be achieved using adaptive measurements.
- 14/05/2013: We have developed a technique for decomposing single qubit channels in terms of a universal gate set. This can be regarded as a Solovay-Kitaev decomposition strategy for channels.
- 16/02/2013: My citation count on Google Scholar has just reached 1000.
- 10/01/2013: I have been selected as an outstanding referee by the American Physical Society.
- 8/01/2013: We have released an erratum on an earlier paper published in 2006. This erratum means that the results are better than in the original paper. We found that adaptive measurements can provide greater accuracy than was predicted originally.
- 20/11/2012: We have released a paper on the simulation of continuous time query algorithms. Continuous time query algorithms are a promising approach for developing quantum algorithms, but they cannot be performed directly. Our work shows that such algorithms can be efficiently simulated on a quantum computer.
- 13/11/2012: Our extended paper on the universality of the Heisenberg limit has now been published in Physical Review A.
- 21/9/2012: We have a new publication in Science! It reports a demonstration of phase measurement enhanced with squeezing for a rapidly fluctuating phase. This was performed by collaborators at the University of Tokyo, and is based on a theoretical proposal by me and Howard Wiseman more than ten years ago.
- 18/9/2012: We have released an extended paper on the universality of the Heisenberg limit. This includes some analytic results giving the expansion with higher-order terms for the Holevo variance. It is available at arXiv:1209.3547.
- 13/9/2012: Hossein Dinani has now joined our group as a PhD student. There is still one PhD scholarship available.
- 13/4/2012: Our latest work showing that the Heisenberg limit is universal has now been published in Physical Review A Rapid Communications.
- 3/01/2012: Alexander Hayes has now joined the group as a new postdoctoral fellow.
- 1/01/2012: My work with Andrew Childs on Hamiltonian simulation and implementation of black-box unitaries has now been published in Quantum Information and Computation. This work gives the most efficient known algorithm for simulation of physical systems.
- 4/11/2011: Some recent publications have brought the Heisenberg limit into question. In new work we have shown that the Heisenberg limit is in fact universal, provided you are averaging over all phase shifts. The preprint is available at arXiv:1111.0788.
- 18/10/2011: Our paper on simulation of time-dependent Hamiltonians with adaptive time steps and discretisation errors has now been published in Journal of Physics A.
- 05/10/2011: My paper with Alex Lvovsky with the more powerful result on linear optical processing of photons has now been published in Physical Review A.
- 04/10/2011: I have now taken up the Future Fellowship at Macquarie University. There will be more news about the fellowship and scholarships soon.
- 19/08/2011: I have been awarded a Future Fellowship at Macquarie University, and will be moving there from IQC in September. Associated with this grant we will have some positions open at Macqurie University. There will be a 1 year postdoctoral fellowship at level A8 available, as well as 2 MQRES PhD scholarships (3 years each).
- 17/03/2011: My paper on nanoscale magnetometry with Ressa Said and Jason Twamley has now been published by Physical Review B.
- 12/12/2010: Our paper on measurement of an unknown phase using entanglement has now been published online by Nature Photonics.
- 16/11/2010: Nathan Wiebe, Barry Sanders and I have shown how to simulate time-dependent Hamiltonians on a quantum computer, using adaptive time steps and taking account of discretisation errors. The preprint is available at arXiv:1011.3489.
- 12/11/2010: My paper with Alex Lvovsky on linear optical processing of photon efficiency has now appeared in Physical Review Letters.
- 01/11/2010: Alex Lvovsky and I have worked out a much more powerful result on linear optical processing of photons. We have now shown that even catalytic improvement of single photon sources is not possible. The preprint is now posted at arXiv:1010.6302.
- 26/10/2010: Our paper on entanglement-enhanced measurement of an unknown phase (arXiv:1003.5213) has now been formally accepted by Nature Photonics.
- 13/10/2010: I've developed a quantum algorithm for solving linear differential equations. The preprint is now posted at arXiv:1010.2745.
To give you an idea of the importance of solving differential
equations, most applications of supercomputers can be expressed in the
form of large systems of differential equations (for example, see this report).
- 06/10/2010: My paper with Alex Lvovsky on linear optical processing of photon efficiency (arXiv:1004.2245) has now been accepted by Physical Review Letters.
- 03/08/2010: My paper with Andrew Childs describing an algorithm for implementing black-box unitaries is now updated (arXiv:0910.4157). It is now far more rigorous, and addresses the more general case of Hamiltonian simulation (hence the change in title).
- 07/05/2010: Our proposed experiment to simulate non-Abelian anyons using photons (arXiv:0906.4578) has now been published in New Journal of Physics.
- 13/04/2010: We (Alex Lvovsky and I) have solved long-standing conjectures about linear optical processing of photon efficiency. The preprint is now available at arXiv:1004.2245. We found the surprising result that it is not possible to improve photon efficiency unless multiphoton components are allowed. This is despite the fact that it is possible to perform error correction to account for photon loss.
- 26/03/2010: My experimental collaborators have now demonstrated our algorithm for entanglement-enhanced measurement of an unknown phase. The preprint is available at arXiv:1003.5213. It uses optimal sequences of 1-, 2- and 4-photon states (postselected on PDC output) to obtain accurate phase measurements.
- 03/03/2010: Our demonstration of phase estimation with time-symmetric quantum smoothing (arXiv:0912.1162) has now been published in Physical Review Letters. This paper was selected for a synopsis in Physics, and is an editor's suggestion.
- 22/01/2010: My paper with Nathan Wiebe and others on ordered operator exponentials (arXiv:0812.0562) has now been published in Journal of Physics A. This work shows how to perform simulations of quantum systems where the Hamiltonian varies as a function of time.
- 12/01/2010: Our paper on the fair sampling assumption (arXiv:0712.2490) has now been published in Physical Review A.
This work shows that the usual fair sampling assumption is not actually
necessary to ensure that the Bell inequality is still valid, and shows
the actual necessary and sufficient conditions.
- 22/10/2009: Andrew Childs and I have developed an algorithm to implement unitaries where the matrix elements are provided by an oracle (arXiv:0910.4157). This breaks the lower bounds for explicit decompositions of unitaries, and achieves scaling close to N2/3, rather than N2.