arXiv subjects

Chitra Rangan

Publications and source records attributed to Chitra Rangan.

4 recordsLinked to original sources

arXiv2026

Dynamical protection of quantum steering and fidelity dynamics in double Jaynes-Cummings model

We investigate the dynamics of Einstein-Podolsky-Rosen (EPR) steering in a double Jaynes-Cummings model, where two initially entangled spatially separated two-level atoms in two cavities interact with independent cavity modes. We study how the intrinsic noise in an initial Werner-type state affects the steering dynamics in this type of quantum optical systems. We also analyze the evolution of steering under experimentally relevant conditions, including atom-cavity detuning and dipole-dipole interactions. We find that both detuning and dipole-dipole coupling help reduce steering sudden death in the system. We further identify a direct correlation between steering and state fidelity, revealing a threshold below which steering disappears. This suggests that fidelity can serve as a practical indicator of steerability in cavity QED systems. Our results provide insight into the controllability and robustness of nonclassical correlations in realistic light-matter platforms.

quant-ph↗

arXiv2018

Trees, Forests, and Stationary States of Quantum Lindblad Systems

In this paper, we study the stationary orbits of quantum Lindblad systems. We show that they can be characterized in terms of trees and forests on a directed graph with edge weights that depend on the Lindblad operators and the eigenbasis of the density operator. For a certain class of typical Lindblad systems, this characterization can be used to find the asymptotic end-states. There is a unique end-state for each basin of the graph (the strongly connected components with no outgoing edges). In most cases, every asymptotic end-state must be a linear combination thereof, but we prove necessary and sufficient conditions under which symmetry in the Lindblad and Hamiltonian operators hide other end-states or stable oscillations between end-states.

quant-ph↗

arXiv2017

Quantum Dynamics of a Two-level System Near a Gold Nanoparticle

The ability to prepare desired states without allowing time for the atomic system to spontaneously decay to the ground state is limited by the fact that Hamiltonian controls cannot affect the purity of the state in question. In this paper, we discuss how a continuous off-resonant electromagnetic wave can be used to prepare a desired final quantum state. With the aid of plasmonic surface-enhancement, by placing a two-level atomic system near a gold nanoparticle, preparation is accomplished in a reduced period of time and with lower electric field intensity while the system purity is improved when compared to an isolated system.

quant-ph↗

arXiv2012

Decoherence Control and Purification of Two-dimensional Quantum Density Matrices under Lindblad Dissipation

Control of quantum dissipative systems can be challenging because control variables are typically part of the system Hamiltonian, which can only generate motion along unitary orbits of the system. To transit between orbits, one must harness the dissipation super-operator. To separate the inter-orbit dynamics from the Hamiltonian dynamics for a generic two-dimensional system, we project the Lindblad master equation onto the set of spectra of the density matrix, and we interpret the location along the orbit to be a new control variable. The resulting differential equation allows us to analyze the controllability of a general two-dimensional Lindblad system, particularly systems where the dissipative term has an anti-symmetric part. We extend this to categorize the possible purifiable systems in two dimensions.

quant-ph↗