Pre-submission Thesis Presentation

Technological advancement over the last few decades has led to a rapid growth in research explorations in the field of quantum information science. This is fuelled by its direct impact on the upcoming quantum technologies with commercial applications. Exponential speed-up of certain tasks in quantum computation as well as enabling some other tasks in quantum information processing such as teleportation, superdense coding, ensuring unconditional security through quantum key distribution protocols, etc., are some of the attractive advantages offered by quantum information science which are either impossible or less efficient in the realm of classical information. Most of these quantum advantages are manifestations of the superposition principle and entanglement which appear only in the framework of quantum mechanics. Entanglement is now seen as an indispensable resource in quantum information processing tasks. However, entanglement is very fragile. It degrades in the presence of noisy environment. The presence of decoherence in computing devices and communication channels, due to the unavoidable and irreversible interaction between the system and environment, causes the degradation in entanglement present in the system as the computation evolves or particles propagate. In some cases, a bipartite entangled state, in the presence of an amplitude damping noise, undergoes a finite time disentanglement which is known as Entanglement Sudden Death (ESD). Since entanglement is an indispensable resource in quantum information processing, manipulation that prolongs the lifetime of entanglement will help realize protocols that would otherwise suffer due to short lifetime of entanglement.

In this talk, I will present the theoretical and experimental results towards “creation, characterization, and manipulation of quantum entanglement in a photonic system”. Specifically, I will discuss a scheme based on local unitary operations on a bipartite entangled state to protect entanglement from undergoing ESD in the presence of an amplitude damping noise. In the process, I will talk about the preparation of a spontaneous parametric down-conversion based type-I polarization entangled photon source and its characterization using quantum state tomography and maximum likelihood estimation. Following this, I will discuss experimental results on an intriguing feature of different entanglement measures for two-qubit pure states: how different entanglement measures capture different deviations of a non-maximally entangled state from the maximally entanglement state and implications therein. Then, I will present the latest experimental results on the demonstration of ESD and ESD-manipulation in a photonic system. In the end, I will conclude the talk with a discussion on the extension of the ESD-manipulation scheme to higher-dimensional systems