Our vision is to explore the quantum behaviour of light and to develop novel quantum technologies that use light for communication and sensing. We address these research questions using spontaneous parametric downconversion and single quantum emitters. We explore the later as systems coupled to optical cavities.
To enable efficient light-matter coupling, a single quantum emitter is typically placed in an engineered photonic environment - a small mode-volume cavity. Such a system allows us to exploit the crucial properties of single quantum emitters.
Single quantum emitters have discrete energy levels that can be excited and driven in a resonant and coherent manner. Since the energy levels of a quantum dot are atom-like the emitted photons exhibit sub-Poissonian statistics. Furthermore, in a special excitation regime called two-photon resonant excitation, photon pairs (biexciton-exciton cascade) can be generated with near unity probability.
Similar to atomic systems quantum dots can be driven resonantly. Therefore, the population can be coherenctly exchanged between the ground and the excited state . This means that by properly choosing the excitation pulse area one can excite the quantum dot with near unity probability. Quantum dot photons can give us polarization and time-bin entanglement. While the degree of polarization entanglement depends predominantly on the symmetry of the quantum dot, the time-bin entanglement can also be obtained from asymmetric dots.
In science and technology, neural networks have been successfully applied to a wide range of problems, including predicting the behaviour of complex systems and analysing large datasets from experiments and simulations. Our goal is to use deep learning to access more information about the quantum system, while requiring fewer measurements.
Sending photons (entangled or not) through optical fibres is a process prone to losses and noise. What happens to the quantum state undergoing such an adventure? Are the quantum states deteriorated in the process? If and when the state stops being quantum? Can we detect the non-classical characteristics of the state that has undergone significant attenuation? All this and many more questions answered.