Non-Markovian homodyne-mediated feedback on a two-level atom: a quantum trajectory treatment

Quantum feedback can stabilize a two-level atom against decoherence (spontaneous emission), putting it into an arbitrary (specified) pure state. This requires perfect homodyne detection of the atomic emission, and instantaneous feedback. Inefficient detection was considered previously by two of us. Here we allow for a non-zero delay time $\tau$ in the feedback circuit. Because a two-level atom is a nonlinear optical system, an analytical solution is not possible. However, quantum trajectories allow a simple numerical simulation of the resulting non-Markovian process. We find the effect of the time delay to be qualitatively similar to that of inefficient detection. The solution of the non-Markovian quantum trajectory will not remain fixed, so that the time-averaged state will be mixed, not pure. In the case where one tries to stabilize the atom in the excited state, an approximate analytical solution to the quantum trajectory is possible. The result, that the purity ($P=2{\rm Tr}[\rho^{2}]-1$) of the average state is given by $P=1-4\gamma\tau$ (where $\gamma$ is the spontaneous emission rate) is found to agree very well with the numerical results.Comment: Changed content, Added references and Corrected typo

Analysis of the impact of marketing strategies in developing and sustaining tourism industry in the Eastvaal region of the Mpumalanga province.

Thesis (MBA)-University of Natal, 2003.The fundamental aim of this study was to analyse the main marketing strategies used in developing and sustaining tourism in the Eastvaal region. An empirical study was conducted amongst the respondents from the local authorities, local tourism organisations, hotels and guesthouses. The information collected was used to write a case about the current reality of tourism marketing in the Eastvaal, which was later evaluated against the ideas presented within the theoretical framework. Furthermore, the study looked at the strategic plans developed by local authorities as well as private sector, which were aimed at encouraging local economic development in general and tourism development in particular. This process was aimed at understanding the effect of private and public sector partnership in the formation of marketing strategies that would impact on sustainable development of tourism industry in the Eastvaal region. A wide range of literature was consulted to understand theoretical base regarding marketing strategies and tourism concepts. However, the study was restricted to the evaluation of the current strategies applied so as to measure their impact in relation to growth and sustainability of tourism in the Eastvaal. Conclusions of the research indicate that an improvement is needed in the current marketing strategies so a to create long-term growth opportunities within the tourism industry