Our research is focused on investigating and understanding the quantum many-body physics of quantum optical systems. These are systems where photons interact with one another through a nonlinear medium — usually atoms or artificialy atoms. These systems are difficult to model and understand for a number of reasons: they are quantum systems whose Hilbert space grows exponentially with the number of particles and they are open systems that are often driven by external sources of light, e.g., lasers. We use a number of different theoretical techniques to model these systems including: Bethe Ansatz scattering matrix techniques, which can give analytic insight into the behaviour of these systems, as well as numerical techniques such as Matrix-Product State methods.
Although we are a theory group, we also aim to work with experimentalists. We look to work with experimental groups in Australia and around the world to observe predictions we make with our theory. We also use these collaborations to further understand different quantum optics platforms.
Some of our current research interests include:
Photon bound states are a type of quantum-correlated light where if one photon is observed, there is an increased likelyhood of observing another photon. These class of states occur as scattering eigenstates of certain kinds of nonlinear media (for example, photons scattering off atoms coupled to waveguides). These bound eigenstates have their own dispersion properties. They also bear a close relation to classical solitons. We are currently exploring whether these states can be generated efficiently and whether they can be used as the basis of a photon number-resolving detector. These bound states can potentially be realized in optical systems and circuit QED.
The propagation of light through ensembles of atoms has been studied for decades. Here the ensemble of atoms can be a gas of cooled atoms, or atoms that are trapped in the vicinity of a nanophotonic waveguide such as a tapered optical nanofiber. Even though these types of experiments have been performed for many years, computing transmitted observables such as the output power and correlation functions remains challenging. This is becauase the number of both photons and atoms in this system can be very large. We are developing a theoretical approach based on a scattering matrix formalism to compute observables of the transmitted light.
Quantum computing is perhaps the most exciting of the emerging quantum technologies. Useful, large-scale quantum computers require error correction which creates a significant overhead for realising a quantum computer. Photon-based systems are an exciting platform for realising fault tolerance because quantum emitters can potentially generate billions of entangled photons per second. We are interested in characterising the noise in these generation schemes for solid-state quantum emitters (particularly semiconductor quantum dots) and determining whether noise levels are sufficiently low to achieve fault tolerance.
We have a number of other research interests such as exploring the nonlinear dynamics of photon transport in subwavelength two-dimensional atomic arrays and time-series machine learning using matrix-product states.
We are always looking for motivated students and postdocs to help us investigate these areas!