Modeling of multiphotonic spectra of molecular complexes

The description of the nature by quantum mechanics is conceptually and computationally challenging. There is an unfulfillment in quantum technologies - it's hard to simulate and control quantum systems. With classical computers it is impossible to simulate quantum systems. In 1982 it was suggested by Richard Feynman and other people, that quantum systems should be simulated by quantum computers. Nevertheless, till this day we have a little progress to achieve this goal. There are different approaches how to build quantum computer, but still there is no practical use of it. The purpose of this work is to investigate water-soluble chlorophyll binding protein (WSCP) as a model for qubit system. WSCP consists of four pigments, which are described by Frenklel excitons. We interpret these excitons as four qubits. The main tool for this work is multiphotonic spectroscopic techniques with help of them we can draw two-dimensional correlation spectra of molecular complexes. We can use a laser to excite two, three or four excitons and observe from spectra their correlations. From broadening of peaks in the spectra we can find out the times of coherence between qubits. We found out that there is coherence between two qubits, which can be manipulated by femtosecond laser. In addition we can equate our system of four excitons (qubits) which is described by Frenkel Hamiltonian to four spin system described by Ising Hamiltonian