Next generation quantum simulators

The prospect of quantum machines outperforming conventional computers can provide ground-breaking capabilities in many fields. The simulation of quantum systems relevant for chemical, biological and industrial purposes, such as molecular reactions, is one of the most promising applications where quantum hardware has the potential to provide an advantage. Very recently, a link between the quantum properties and dynamics of molecules and the behaviour of photons (single particles of light) evolving in interferometric networks has been developed [1,2], opening the possibility for efficient quantum chemistry simulations based on boson sampling. The implementation of such simulations for practically relevant problems requires photonic hardware able to generate, control, and process quantum states of light on a large scale. Integrated quantum photonics, where stable and reconfigurable optical circuits embedding hundreds of optical components [3] and large photonic states [4] can be integrated on millimetre-scale chips, is the ideal platform to achieve that. These capabilities set integrated photonics on route to show a quantum advantage over classical methods for quantum chemistry simulations.

In this PhD project, the candidate will work on mapping and solving quantum simulation problems relevant to molecular dynamics and electronic structure on integrated quantum photonic devices. The project will be performed within the Quantum Engineering Technology Labs, which saw the first realisations of photonic quantum chips and has a primary role worldwide in the field. Working closely with other researchers in the group, the candidate will develop a strong background in photonic quantum information processing, quantum simulation, integrated optics, and design of photonic circuits. During the project, the candidate will have the possibility to work both on the theoretical aspects of mapping molecular systems into photons, and experimentally implementing the quantum simulation on a large scale photonic device. The candidate should have an initial background in quantum optics and know at least one standard scientific programming language (Python, C++, MATLAB, Mathematica).

In the first year, the student will deepen their understanding of quantum simulation and their ability to work in a state-of-the-art quantum photonic laboratory. The program of work will start by expanding the applicability of recently developed techniques [1, 2] to problems of general relevance such as the study of molecular dynamics well beyond the harmonic approximation and design quantum photonic devices and experiments for quantum simulation. The theoretical work will be conducted in collaboration with more senior students, postdocs and external collaborators expert in quantum chemistry. The chip designs will be submitted to commercial fabrication facilities for realisation.

In the second year, upon receiving the devices designed during the first year, the experimental work will become more prominent, requiring the testing and characterisation of these devices, followed by proof of principle demonstrations of more complex molecular dynamics. These demonstrations will include Boson sampling experiments with chips integrating fundamental components, such as quantum states of light sources, filters and interferometric networks, using off-chip superconductive nanowires detectors. These quantum simulators will be then employed in practical applications such as the study of dissociation pathways and chemical reaction optimisation.

In the last year, the student will focus on completing the experiments and optimising performances in order to increase the number of photons and then the complexity of the accessible simulations. The final part of their PhD will be devoted to the writing of journal articles and their thesis.