Detail:
Abstract: Coherent Energy Transfer (ET) is a common quantum phenomenon in nano-structure mesoscopic systems. However, the notions of coherence, as well as population, are basis set dependent. We suggest an approach, based on diagonalization of the reduced system density matrix at all times, that provides a basis-set independent characterization of coherent effects in energy transfer. We explore a possibility of monitoring coherent energy transfer using single-molecule measurements. This necessarily involves the Quantum Measurement (QM) theory due to the quantum nature of coherent energy transfer and repeated character of a single-molecule measurement. Adopting a Weak Measurement (WM) concept we derive a version of a stochastic trajectory formalism that is very close to an in a lab setting, by dealing with the probabilities of continuous electrical current measurement in the detector. We show that the correlation functions of the measured currents, available from statistical processing of experimental data, contain detailed information on the reduced density matrix evolution, and further develop response theory for multi-time correlation functions. This response theory is formally reminiscent o a standard optical response counterpart, with one interesting difference: the role of the driving field is also played by the QM via its intrinsic property to affect the measured system.
