Entanglement for Qubit and Qudit in Single Photoionization of Rotationally State Selected, Oriented C3v Polyatomic Molecules

Multidimensional quantum systems (qudits), as a generalization of two-level quantum systems (qubits), can exhibit distinct quantum properties, provide higher capacity and noise robustness in quantum communications. Qudits also offer higher efficiency and flexibility in quantum computing. Present paper studies the bipartite entanglement betwixt a molecular photoion (qudit) and photoelectron (qubit) produced in the photoionization from rotationally state selected, oriented polyatomic molecule without observing spin-orbit interaction (SOI). In absence of SOI, Russell-Saunders (RS) coupling is applicable. The dimension of ionic qudit depends on its electronic state. The degree of entanglement is quantified by the concurrence obtained from the elements of density matrix (EDM) for photoionization. The theoretical formulation for entanglement has been developed for photoionization of rotationally state selected, oriented C3v molecules. It is applied, as an example, to photoionization in 13a₁² orbital of a state selected oriented CH3I in a pure JK_JM_J rotational state. We find that the entanglement depends significantly on the rotational states of the molecule as well as either or both on the directions of molecular orientation, of spin quantization, and of the incident beam along with its polarization. A significant effect on entanglement properties due to the circular dichroism (CD) has also been observed.