Browsing by Author "Gharat, R.M."

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Circuit Complexity in Interacting Quenched Quantum Field Theory
(MDPI, 2023) Choudhury, S.; Gharat, R.M.; Mandal, S.; Pandey, N.
In this work, we explore the effects of quantum quenching on the circuit complexity of quenched quantum field theory with weakly coupled quartic interactions. We use the invariant operator method under a perturbative framework to compute the ground state of this system. We give the analytical expressions for specific reference and target states using the ground state of the system. Using a particular cost functional, we show the analytical computation of circuit complexity for the quenched and interacting field theory. Furthermore, we give a numerical estimate of circuit complexity with respect to the quench rate, (Formula presented.), for two coupled oscillators. The parametric variation in the unambiguous contribution of the circuit complexity for an arbitrary number of oscillators has been studied with respect to the dimensionless parameter (Formula presented.)). We comment on the variation in the circuit complexity for different values of coupling strength, different numbers of oscillators and even in different dimensions. © 2023 by the authors.
Entanglement in interacting quenched two-body coupled oscillator system
(American Physical Society, 2022) Choudhury, S.; Gharat, R.M.; Mandal, S.; Pandey, N.; Roy, A.; Sarker, P.
In this work, we explore the effects of a quantum quench on the entanglement measures of a two-body coupled oscillator system having quartic interaction. We use the invariant operator method, under a perturbative framework, for computing the ground state of this system. We give the analytical expressions for the total and reduced density matrix of the system having non-Gaussian, quartic interaction terms. Using this reduced density matrix, we show the analytical calculation of two entanglement measures viz., Von Neumann entanglement entropy using replica trick and Renyi entanglement entropy. Further, we give a numerical estimate of these entanglement measures with respect to the dimensionless parameter (t/δt) and show its behavior in the three regimes, i.e., late time behavior, around the quench point and the early time behavior. We comment on the variation of these entanglement measures for different orders of coupling strength. The variation of Renyi entropy of different orders has also been discussed. © 2022 authors. Published by the American Physical Society.
Schwinger–Keldysh Path Integral Formalism for a Quenched Quantum Inverted Oscillator
(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Choudhury, S.; Dey, S.; Gharat, R.M.; Mandal, S.; Pandey, N.
In this work, we study the time-dependent behavior of quantum correlations of a system of an inverted oscillator governed by out-of-equilibrium dynamics using the well-known Schwinger–Keldysh formalism in the presence of quantum mechanical quench. Considering a generalized structure of a time-dependent Hamiltonian for an inverted oscillator system, we use the invariant operator method to obtain its eigenstate and continuous energy eigenvalues. Using the expression for the eigenstate, we further derive the most general expression for the generating function as well as the out-of-time-ordered correlators (OTOCs) for the given system using this formalism. Further, considering the time-dependent coupling and frequency of the quantum inverted oscillator characterized by quench parameters, we comment on the dynamical behavior, specifically the early, intermediate and late time-dependent features of the OTOC for the quenched quantum inverted oscillator. Next, we study a specific case, where the system of an inverted oscillator exhibits chaotic behavior by computing the quantum Lyapunov exponent from the time-dependent behavior of OTOCs in the presence of the given quench profile. © 2024 by the authors.