Quantum Feedback-Enhanced Discord in T-Shaped Plasmonic Waveguides with Embedded Cavity

This theoretical study presents a hybrid quantum system that combines the geometry of a T-shaped plasmonic waveguide with an embedded common cavityand applies quantum feedback control to enhance and preserve quantum discord between two quantum dots (QDs). Building upon previous work on entanglement generation in T-shaped waveguides and feedback-enhanced discord in V-shaped waveguides, we demonstrate that the T-shape geometry with its specific boundary conditions, coupled with active feedback, offers superior control over quantum correlations. The system consists of two QDs placed at strategic positions within the waveguide: one at the node and the other at the end of the finite arm, both embedded in a common cavity. We derive the system’s dynamics using a real space Hamiltonian approach and solve the time-independent Schrodinger equation to obtain scattering amplitudes. Quantum discord is then calculated for the two-QD subsystem. Our results show that by applying symmetric quantum feedback based on Wiseman-Milburn formalism, we can significantly enhance the steady state quantum discord, achieving values up to Dss ≈ 0.38 for Werner states under optimal parameter conditions. We identify three distinct decay regimes for discord and demonstrate that parameters such as the phase accumulation (α = kL, where k = \omega/vg is the plasmon wave vector) along the finite arm, providing cavity-QD couplings (J1, J2), detunings (\delta_j , \delta_c), and dipole-dipole interaction strength (f ) provide multiple control knobs for tuning quantum correlations. This work provides a comprehensive framework for designing actively controlled nanophotonic quantum devices that leverage both plasmonic field enhancement and quantum feedback for robust quantum information processing at room temperature.