arXiv subjects

Sagarika Basak

Publications and source records attributed to Sagarika Basak.

5 recordsLinked to original sources

arXiv2026

Invariant-based master equation applied to driven qutrit coupled to a bath and a leaky cavity

We employ a generalized approach to the master equation for driven open $N$-level ($N>2$) quantum systems using Lewis-Riesenfeld invariants, which avoids the driving-strength restrictions inherent to conventional approaches. We show that the invariant-based master equation provides a unifying generalized framework, which reduces to the frequently employed laboratory-frame master equations and the less frequently employed rotating-frame master equation framework under appropriate simplifications. Extending the prototypical two-level system, we show that the inclusion of another state coupled to the ground state via reservoir-induced dephasing gives rise to qualitatively new dissipative behaviors that are, in general, not captured by standard approximations. We also apply the invariant-based master equation framework to a driven quantum dot coupled to a leaky cavity, demonstrating the framework's ability to capture relevant dissipative dynamics without additional assumptions. Our work paves the way for quantum-control applications in the presence of dissipation.

quant-ph↗

arXiv2025

Quantum transport in 1D Hubbard model: Drude weights and Seebeck effect

The Drude weight (DW) is an essential quantity that characterizes the quantum transport properties of many-body systems. However, a rigorous understanding and exact computation of DWs, particularly for strongly correlated systems with doping, still remain elusive. In this Letter, taking advantage of the quantum integrability, we calculate exactly the DWs and Seebeck effect (SE) for generic filling factor in one-dimensional (1D) Fermi-Hubbard model with arbitrary interaction strengths and magnetic fields. We build up its intrinsic connection to the Luttinger parameters, and derive universal scaling laws for DWs across phase transitions. Our results provide a deep understanding of mutual influences in transport between the spin and the charge degrees of freedom, showing a counterintuitive subtle spin-charge coupling effect and uncovering the microscopic origin of the (spin) Seebeck effects in thermal conductivity. Finally, we propose an experimental protocol to measure the DWs in ultracold atomic systems.

cond-mat.str-el↗

arXiv2023

A generalized effective spin-chain formalism for strongly interacting spinor gases in optical lattice

A generalized effective spin-chain model is developed for studies of strongly interacting spinor gases in a one-dimensional (1D) optical lattice. The spinor gas is mapped to a system of spinless fermions and a spin-chain. A generalized effective spin-chain Hamiltonian that acts on the mapped system is developed to study the static and dynamic properties of the spinor gas. This provides a computationally efficient alternative tool to study strongly interacting spinor gases in 1D lattice systems. This formalism permits the study of spinor gases with arbitrary spin and statistics, providing a generalized approach for 1D strongly interacting gases. By virtue of its simplicity, it provides an easier tool to study and gain deeper insights into the system. In combination with the model defined previously for continuum systems, a unified framework is developed. Studying the mapped system using this formalism recreates the physics of spinor gas in 1D lattice. Additionally, the time evolution of a quenched system is studied. The generalized effective spin-chain formalism has potential applications in the study of a multitude of interesting phenomena arising in lattice systems such as high-$T_c$ superconductivity and the spin-coherent \& spin-incoherent Luttinger liquid regimes.

cond-mat.quant-gas↗

arXiv2021

Strongly Interacting Two-component Coupled Bose Gas in Optical Lattices

Two-component coupled Bose gas in a 1D optical lattice is examined. In addition to the postulated Mott insulator and superfluid phases, multiple bosonic components manifest spin degrees of freedom. Coupling of the components in the Bose gas leads to substantial change in the previously observed spin phases, giving rise to new effective spin Hamiltonian and unraveling remarkable spin correlations. The system exhibiting ferromagnetic and non-ferromagnetic spin phases for on-site intra-component interaction stronger than inter-component interaction switches from first-order to second-order phase transition between the spin phases upon introduction of coupling, on which is dependent the transition width. For comparable on-site inter- and intra- component interaction, with coupling, instead of one, two spin phases emerge with a second-order phase transition. Exact diagonalization and Variational Monte Carlo (VMC) with stochastic minimization on Entangled Plaquette State (EPS) bestow a unique and enhanced perspective into the system beyond the scope of a mean-field treatment.

cond-mat.quant-gas↗

arXiv2017

Periodically Driven Array of Single Rydberg Atoms

An array of single Rydberg atoms driven by a frequency modulated light field is studied. The periodic modulation effectively modifies the Rabi coupling, leading to unprecedented dynamics in the presence of Rydberg-Rydberg interactions. They include state dependent population trapping, the Rydberg blockade for small and anti-blockades at large interaction strengths. Interestingly, the Schrieffer-wolf transformation reveals a fundamental process in Rydberg gases, correlated Rabi oscillations, arising from the long-range interactions, provides an alternative depiction for Rydberg blockade and it exhibits a nontrivial behaviour in the presence of periodic modulation. The dynamical localization of a many body configuration in a driven Rydberg-lattice is discussed.

cond-mat.quant-gas↗