Thesis : Arunangshu DEBNATH (LCAR) September 2013

Dynamics and Control of open quantum systems : Applications to exciton dynamics in quantum dots and vibrational dynamics in carboxyhemoglobin

Abstract : This thesis work analyses aspects of dissipative quantum dynamics, with a view to look for further possibilities of controlling the dynamics with shaped laser pulses.The first part concerns the problem of efficient population transfer in mesoscopic zero-dimensional solid state systems - InAs quantum dots embedded in GaAs matrix. In these systems the consequences of laser driving induced dissipation of exciton dynamics are analyzed, in relation to adiabatic population transfer. Specifically, the problem of robust creation of exciton and biexciton states are addressed through numerical simulations and analytical approaches using a non-Markovian density matrix based analysis, suitable for dealing with dissipative quantum dynamics under strong laser fields. A physical picture describing phonon induced dissipation among dressed state has emerged as a consistent interpretation of the underlying dynamics. Furthermore, suitable parameter regimes where efficient population transfer can be achieved are proposed.The second part deals with the population transfer to high lying vibrational states of the CO stretching mode of carboxy-hemoglobin molecule in the native protein environment. On the basis of a fluctuating potential for the CO stretching mode, ultrafast pump-probe spectra are simulated using quantum wave packet propagation. To this end, Local Control Theory was employed to find design a set of laser pulses which accomplish the ‘vibrational ladder climbing’ and selective state preparation despite the detrimental fluctuations induced by the protein environment. These results will be providing benchmarks for the future experimental efforts.

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