| dc.description.abstract | Quantum entanglement is central to many quantum technologies and is an indispensable ingredient of quantum information theory. These facts make the generation, characterization and quantification of entangled states unavoidable tasks, beside all their fundamental significance. As a particular example of such applications one may consider quantum metrology in which quantum entanglement is shown to have a significant role for beating the classical limits. However, generation, characterization and quantification of suitable entangled states are challenging tasks, in general.
In this dissertation, we introduce new platforms for engineering multipartite entangled states that are shown to be useful for quantum information processing and quantum metrology applications. In particular, we introduce new methods which can be used for generating N00N states, as one of the most challenging states to generate, enabling realization of such states in both photonic and spintronic architectures. We sketch a rather generic quantum circuit, for the N00N state generation, that could be realized in various quantum systems. Furthermore, we extend the platform for the generation of states beyond the N00N state. Typical examples of such sates could be entangled coherent or squeezed states, for instance, that of specific importance for quantum information and metrology applications. Furthermore, we extend the protocol for the multipartite state scenario. Also, we demonstrate that attaining the ultimate sensitivity in phase estimation is not an exclusive property of the N00N states. As a result, we find a large class of entangled states that could provide us with the ultimate sensitivity achieved by the N00N state.
As a part of our effort for the N00N state generation, we develop a new scheme where N00N states could be realized in two ensembles of nitrogen--vacancy (NV) centers in diamond. This could be interesting by noting the fact that NV centers in diamonds provide a remarkably long coherence time, even at the room temperature. This opens up new possibilities for protecting N00N states against decoherence.
Moreover, having the long coherence time of the ensembles of the NV centers, we show that a hybrid quantum system consisting of three ensembles of NV centers coupled to a superconducting device enables the generation of controllable macroscopic multipartite entangled states, which could be used as a building block for quantum networks.
Furthermore, we investigate entanglement of nonorthogonal states in details, and more specifically, we obtain a closed-form analytical expression for the entanglement degree of a multipartite qutrit state, that offers a quantitative measure for entanglement $n$-mode nonorthogonal qutrit states with an arbitrary $n$. Such higher dimensional entangled states could be useful in quantum communication protocols.
Finally, we introduce a new configuration where any pair of quantum states can perfectly be swapped between two quantum resonators enabling a realization of a universal swap operation in photonics systems. This can serve as a building block of various quantum information processors. | en |
