Confinement induced structural and entropic features of positronic systems

In this study, we explore various structural and quantum information-theoretic measures of the ground state of Ps⁻ Ps - and its subsystem Ps under the influence of pressure-induced spatial confinement within the Ritz variational framework. Various geometrical quantities, such as radial and angular moments, undergo significant modification with the changes in the confinement parameters. Evidently, the annihilation rates for both systems increase as thermodynamic pressure increases in the systems. Further, the quantum entanglement measure, quantified through von Neumann entropy, reveals the possibility of manipulating the entanglement strength in Ps⁻ Ps - , including the emergence of a minimally entangled state. Moreover, Shannon and Fisher information entropies demonstrate the localization effects as pressure increases in both systems, along with a pressure-induced quantum similarity measure between the two systems under consideration.