Quantum amplification of engineered classical states of light

Abstract

Since their first conception, quantum technologies are now starting to become a reality promising to improve our everyday life with the prospect of enhanced non-invasive imaging systems, highly efficient and ultra sensitive sensors, and absolute security in digital telecommunications. Enormous advancements in terms of characterisation, manipulation, and detection of single quantum states have seen the birth of a plethora of different platforms and protocols capable of achieving such challenging tasks. Quantum communications, in particular, have already shown promising results in real life implementations closing the distance to what many have referred to as the quantum internet – the next generation of global telecommunications. However, one of the several roadblocks preventing the implementation of such technology on a global scale is quantum amplification. This Thesis introduces a novel probabilistic quantum amplifier for exotic quantum states (thermal state) showcasing its ability to manipulate their intensities via a unique double state displacement method. Additionally, the thesis presents a probabilistic quantum amplifier based on the coherent state comparison technique with the addition of an active feed-forward mechanism capable of simultaneously improving key quantum properties of a state and enhancing the amplifier’s success probability. The Thesis also shows the experimental work undertaken in the context of quantum random number generation highlighting the limitations of optical heterodyne detection and setting a benchmark for future evaluations of similar systems.