Quantum Photonic Integrated Circuits Operating at Cryogenic Temperatures

Photonic Integrated Circuits (PICs) have developed rapidly over the last decade, enabling the miniaturisation of optical systems onto a single chip. Furthermore, the integration of electronics and photonics on a chip have underpinned advances in telecommunications, sensing, and recently, quantum information processing. In quantum systems photons can be used as a communications layer between solid-state quantum nodes or as qubits themselves. The compact size and mechanical stability of PICs make them an attractive option for the routing and processing of optical signals at significant scale.

One major challenge lies in the reconfigurability of these PICs. To allow for flexible and controllable circuits, a mechanism for tuning optical components is necessary. The current state of the art in the field for telecommunications applications uses PIN junction diodes or thermal heater elements to create absorption or refractive index changes in the waveguiding material. For quantum systems neither of these methods are ideal, with the former introducing noise photons to the circuit and the latter introducing thermal sources into the cryogenic conditions necessary for many of the single photon source and detector technologies employed.

In this project a new method for tuning PICs will be developed that is compatible with cryogenic and low power consumption operation. To achieve this a hybrid integration method will be used to integrate different optical materials together on a single chip. Second order non-linear response materials will be used to create refractive index changes by direct electronic control, compatible with operation in cryogenic environments.

The student will carry out numerical simulations of devices to optimise the geometries and circuit layouts which will then be used for fabrication of PIC systems. The student will be responsible for the measurement of the resultant PIC systems in state-of-the-art optical laboratories with access to classical and single photon sensitive measurement equipment. Measurement results will be used to feedback into optimisation of the fabrication process with final circuit designs being used to implement quantum information processing experiments. The student will be part of a larger research group with the opportunity to work with others in a collegiate and enthusiastic team. Research findings will be published in high impact journals with the opportunity to present at an international conference.