Incoherent Control Of Optical Measurements Using Quantum Thermodynamics

The technological advancement in the modern optical technology emphasizes the importance of engineering the light-matter interaction in open quantum systems such as the biological molecules,the complex material etc.The effects of the environment impact significantly the ability to control the optical measurements in such systems.The methods such as the optimal control theory and others are based on the optimization of unitary evolution of the system dynamics in Hilbert space and thus are limited to the isolated systems.On the other hand,the field of quantum thermodynamics and quantum thermal machines is routinely dealing with the open quantum system’s dynamics in the Liouville space.The concepts of details balance,the Carnot cycle exemplify the optimization process with respect to system-environment interaction.Drawing the analogy between the quantum heat engine（QHE）which transfers the heat from the hot to the cold bath and extracts the useful work and the optical pumpprobe measurement in a molecular system,where the energy is transferred from the pump to the probe optical pulse we developed an incoherent control method for the optical measurements using the formalism of quantum thermodynamics.The following thesis consists of the two parts:The Part Ⅰ contains five chapters:Chapter Ⅰ.1 recapitulates the earlier advancement in the theoretical and the experimental quantum thermodynamics in the description of the QHE.Chapter Ⅰ.2 explains the basic mathematical framework of the system plus reservoir approach in quantum theory and its approximation for the weak system bath interaction.In Chapter Ⅰ.3 we describe the previous well-established techniques that have been applied to the coherent control methods for the studies of isolated system dynamics.Chapter Ⅰ.4 mainly discusses the quantum definition of thermal quantities and mathematical formulation of continuous three-level heat engine.We further discuss the well established output power maximization technique in the high and the low temperature limits.Chapter Ⅰ.5 mainly focuses on the basic mathematical framework in the regime typical for the spectroscopic signals derived using perturbative expansions over the light-matter interactions.We present the diagrammatic formalism for the pump-probe signal to the third order in the field-matter interaction.The part Ⅱ consists of three chapters,the whole of which summarizes our main findings.Chapter Ⅱ.6 contains a model in which the optical pump-probe signals can be viewed as the work done by the material system while transferring the energy between the two coherent baths（from the pump to probe）.In thermodynamics,a heat engine,such as a laser,is a device that performs the similar work while operating between the two thermal baths.We propose an "incoherent" control procedure for the optical signals using the physics of a quantum heat engine.By combining a coherent laser excitation of an electronically excited state of a molecule followed by the thermal relaxation we introduce an effective thermal bath treating the stimulated emission of probe photons as work performed by the heat engine.We optimize the power and the efficiency using the control parameters of the pump laser utilizing a four-level system design in the strong and the weak coupling regimes illustrating its equivalence with the thermodynamic cycle of the heat engine.Chapter Ⅱ.7 presents a consistent optimization procedure for the two-photon pump excitation followed by the classical probe pulse.Assigning an effective hot bath for the two-entangled-photon pump we recast the transmission of the classical probe as a work in a quantum heat engine framework.We demonstrate that the maximum work in such a heat engine can exceed that for the classical two-photon and onephoton pumps,due to the control of entanglement time and the different scaling of the two-photon absorption possibility with respect to the pump intensity.In the same time the efficiency at maximum power can be attributed to the conventional boundaries obtained for a three-level quantum heat engine.Our results pave the way for the incoherent control and the optimization of the optical measurements in the open quantum systems that involve two-photon processes with the quantum light.In the chapter Ⅱ.8,we summarize the complete thesis and describe the future direction of research suggesting the possible experimental demonstration based on our model.