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Abstract
Experiments were carried out to examine the basic properties and utility of several quantum states and operations of light. These experiments comprised mostly of the general elements of Gaussian quantum optics but require in addition a pair of special operations known as photon addition and noiseless amplification.
It is shown that a number of important physical quantities are increased by the action of photon addition or noiseless amplification on entangled states, including the distillable entanglement and the rate of distributing secret keys using these entangled states.
It is further shown that noiseless amplification can be embedded in a natural way into feed-forward setups such as quantum teleportation and measurement-based quantum gates, with the valuable effect of suppressing decoherence in these devices.
In some cases, it is observed that multiple quantum operations could merge to produce new quantum effects: the combination of photon addition and coherent displacement leads to strong cubic phase shifts; quantum teleportation combined with noiseless amplification has the remarkable ability to purify displaced thermal states without reducing the displacement.
In the special instance of photon addition on thermal states, a counter-intuitive transformation of the state of light arises which we verified by experiment, and which serves as a test of the validity of quantum mechanics.
The facts established in this thesis have direct implications for quantum technology, including the provision of a route towards universal quantum computation and a new method for removing thermal decoherence without quantum error correction and with a far simpler setup.
