Steady-State Two Atom Entanglement in a Pumped Cavity

In this paper we explore the possibility of a steady-state entanglement of two two-level atoms inside a pumped cavity by taking into account cavity leakage and the spontaneous emission of photons by the atoms. We describe the system in the dressed state picture in which the coherence is built into the dressed states while transitions between the dressed states are incoherent. Our model assumes the vacuum Rabi splitting of the dressed states to be much larger than any of the decay parameters of the system which allows atom-field coherence to build up before any decay process takes over. We show that, under our model, a pumping field cannot entangle two closed two-level atoms inside the cavity in the steady-state, but a steady-state entanglement can be achieved with two open two-level atoms.Comment: 19 pages, 5 figure

Robust Multi-Partite Multi-Level Quantum Protocols

We present a tripartite three-level state that allows a secret sharing protocol among the three parties, or a quantum key distribution protocol between any two parties. The state used in this scheme contains entanglement even after one system is traced out. We show how to utilize this residual entanglement for quantum key distribution purposes, and propose a realization of the scheme using entanglement of orbital angular momentum states of photons.Comment: 9 pages, 2 figure

Generation and applications of multi-partite multi-level quantum entanglement

Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2010.In this thesis we present a new multi-level multi-partite quantum protocol which utilizes residual entanglement in order to generate a secure key for cryptographic communication. Furthermore, the multi-level multi-partite quantum state we use for the cryptographic key generation can also be used for a secret sharing protocol. We propose a possible realization of this quantum protocol using the orbital angular momentum degree of freedom of photons. We also investigate the steady-state entanglement between atoms by describing the system in the dressed state picture which enables us to determine where the entanglement lies in the excitation manifold. This new approach we take to investigate entanglement also shows how the weak field assumption fails regardless of how weak the applied field is when considering the entanglement between the atoms. We demonstrate that two closed two-level atoms inside a cavity can be entangled in the steady state with the use of a non-linear mirror, and two open two-level atoms can be entangled in a cavity through optically pumping population out of the dressed state manifolds. Finally, we explore a new type of dark state which is a dark state of a collection of atoms. These dark states are entangled, and we offer the simplest example of such a state using a J1/2 - J1/2 system. We demonstrate how one can simplify the problem by exploiting symmetries of the system, and show the general procedure to find these states