Controlling Environmental Interactions for Novel Solid-State Quantum Technologies

Quantum dots (QDs) are nanoscale regions of semiconductor, embedded within a much larger host of a second semiconductor. The differing properties of the two semiconductors mean that single particles of charge (electrons) can be trapped within a QD, allowing for study of light-matter interactions on a single particle level. In particular, QDs form an excellent source of the quantum states of light (photons) that are required for many exciting new quantum technologies such as secure communication and enhanced sensing. A consequence of the solid-state host is that the QD interacts with its local environment, a particularly important example being quantised vibrations of the lattice, termed phonons. These interactions have typically been considered an unwelcome but unavoidable consequence of working with QDs and other similar solid-state systems. This proposal aims to demonstrate that through appropriate nano-fabrication and control of the QD geometry, the interaction of the QD with both its optical (photonic) and vibrational (phononic) environments can be controlled. By realising such control over environmental interactions, the impact of phonon interactions on the photons emitted can be almost eliminated, increasing the efficiency and quality of the QD photon source to support new applications. Furthermore, the need for extreme cryogenic cooling can be greatly reduced, removing a significant barrier to quantum technologies applications. Harnessing these developments, several novel quantum technologies will be developed based on the QD platform. Quantum 2-photon microscopy offers the potential to perform imaging of delicate samples that would be damaged by the intense light fields required for current methods. Meanwhile, high sensitivity optical sensing can be realised by using phonon interactions to "squeeze" the uncertainty in photons emitted by the QD. Finally, quantum data locking offers the potential for quantum-secured communication with a significantly higher efficiency than existing methods.