###### Theory of quantum measurement and control in semiconductor qubits

*Grand challenge: Develop design principles for robust control of hybrid quantum systems and demonstrate their utility in experimental applications.*

Together with the team of Amir Yacoby at Harvard, we are investigating how electrons in a semiconductor chip can be used to store and process quantum information. These spins have the potential for very long coherence times relative to gate operation times, but experience a noisy environment from the atomic nuclei of all the surrounding semiconductor atoms. Left on their own, these nuclei will destroy the quantum nature of the electron very quickly, in a few billionths of a second. We have invented a new technique where we use the electron to monitor its environment, very quickly learn the effect of all of these nuclei, and then use this information to compensate for its effect. This research was published in 2014 in Nature Communications.

###### Controlling electron spin in semiconductor quantum devices

*Grand challenge: Realise new and otherwise inaccessible regimes of physics through the construction of hybrid quantum systems. *

Single electrons individually trapped and manipulated in semiconductors are one of the most promising avenues for engineered quantum systems. This project investigates the ways in which the magnetic moment, or spin, of these electrons can be controlled, either electrically or through applying microwaves, and how acoustic vibrations, or phonons, affect this control. These results highlight the role of the phononic environment in understanding the driven dynamics of coherent quantum systems and provide a path for transducing quantum information between photons, phonons, spins and charge. The work is a strong collaboration between theorists CI Tom Stace (UQ) and CI Andrew Doherty (Sydney) and the experimental team of CI Reilly’s laboratory (Sydney). This work has been published in Nature Communications.

###### Quantum matter

*Grand challenge: Address key fundamental theoretical questions.*

*Grand challenge: Preserving quantum states against decoherence indefinitely.*

The Synthetic Quantum Systems program aims to address the key fundamental theoretical questions: how can we create and harness quantum matter to process information in new ways, and what new principles can we learn from a classification of this matter? We theoretically construct and explore new phases of strongly-coupled quantum many-body systems that exhibit powerful exotic properties such as topological order, and direct these properties towards applications such as quantum memories and processors.

###### Quantum chemistry with quantum simulators

*Grand challenge: Produce programmable quantum simulators capable of outperforming the best classical technology.*

One of the most anticipated applications of quantum simulations is to increase the accuracy of calculations in quantum chemistry. For example, the energy of metastable transition states of even rather small molecules can be critical to understanding industrially significant chemical reactions that involve catalysts. The highest accuracy simulations performed currently to estimate such energies are termed full configuration interaction simulations, and if they could be performed on systems involving as few as one hundred orbitals, this would already be an enormous advance. This work, in collaboration with researchers at the University of Sherbrooke and Microsoft Research, aims to investigate the usefulness of digital quantum simulators for performing full configuration interaction simulations, as compared to classical devices.