Ranjan Modak
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View article: Subsystem localization in a two-leg ladder system
Subsystem localization in a two-leg ladder system Open
We consider a ladder system where one leg, referred to as the ``bath", is governed by an Aubry-André (AA) type Hamiltonian, while the other leg, termed the ``subsystem", follows a standard tight-binding Hamiltonian. We investigate the loca…
View article: Dependence of Krylov complexity saturation on the initial operator and state
Dependence of Krylov complexity saturation on the initial operator and state Open
Krylov complexity, a quantum complexity measure which uniquely characterizes the spread of a quantum state or an operator, has recently been studied in the context of quantum chaos. However, the definitiveness of this measure as a chaos qu…
View article: Measurement-induced phase transition in periodically driven free-fermionic systems
Measurement-induced phase transition in periodically driven free-fermionic systems Open
It is well known that unitary evolution tends to increase entanglement, whereas continuous monitoring counteracts this growth by pinning the wavefunction trajectories to the eigenstates of the measurement operators. In this work, we invest…
View article: Topological properties of curved spacetime Su-Schrieffer-Heeger model
Topological properties of curved spacetime Su-Schrieffer-Heeger model Open
The Su-Schrieffer-Heeger (SSH) model, a prime example of a one-dimensional topologically nontrivial insulator, has been extensively studied in flat space-time. In recent times, many studies have been conducted to understand the properties …
View article: Probing quantum phase transition via quantum speed limit
Probing quantum phase transition via quantum speed limit Open
Quantum speed limit (QSL) is the lower bound on the time required for a state to evolve to a desired final state under a given Hamiltonian evolution. Three well-known QSLs exist Mandelstam-Tamm (MT), Margolus-Levitin (ML), and dual ML (ML$…
View article: Quest for optimal quantum resetting: protocols for a particle on a chain
Quest for optimal quantum resetting: protocols for a particle on a chain Open
In the classical context, it is well known that, sometimes, if the search does not find its target, it is better to start the process anew again, known as resetting. The quantum counterpart of resetting also indicates speeding up the detec…
View article: Ergodic and mixing quantum channels: From two-qubit to many-body quantum systems
Ergodic and mixing quantum channels: From two-qubit to many-body quantum systems Open
The development of classical ergodic theory has had a significant impact in the areas of mathematics, physics, and, in general, applied sciences. The quantum ergodic theory of Hamiltonian dynamics has its motivations to understand thermody…
View article: One-dimensional Lévy quasicrystal
One-dimensional Lévy quasicrystal Open
Space-fractional quantum mechanics (SFQM) is a generalization of the standard quantum mechanics when the Brownian trajectories in Feynman path integrals are replaced by Lévy flights. We introduce Lévy quasicrystal by discretizing the space…
View article: Hellmann Feynman Theorem in Non-Hermitian system
Hellmann Feynman Theorem in Non-Hermitian system Open
We revisit the celebrated Hellmann-Feynman theorem (HFT) in the PT invariant non-Hermitian quantum physics framework. We derive a modified version of HFT by changing the definition of inner product and explicitly show that it holds good fo…
View article: Engineering skin effect across a junction of Hermitian and non-Hermitian lattice
Engineering skin effect across a junction of Hermitian and non-Hermitian lattice Open
We study a system where the two edges of a non-Hermitian lattice with asymmetric nearest-neighbor hopping are connected with two Hermitian lattices with symmetric nearest-neighbor hopping. In the absence of those Hermitian lattices, the ma…
View article: Non-Hermitian description of sharp quantum resetting
Non-Hermitian description of sharp quantum resetting Open
We study a non-interacting quantum particle, moving on a one-dimensional lattice, which is subjected to repetitive measurements. We investigate the consequence when such motion is interrupted and restarted from the same initial configurati…
View article: Complexity growth for one-dimensional free-fermionic lattice models
Complexity growth for one-dimensional free-fermionic lattice models Open
Complexity plays a very important part in quantum computing and simulation where it acts as a measure of the minimal number of gates that are required to implement a unitary circuit. We study the lower bound of the complexity [Eisert, Phys…
View article: PT-Symmetry Breaking Transitions in Polymeric Systems
PT-Symmetry Breaking Transitions in Polymeric Systems Open
We show that classical DNA unzipping transition which is equivalently described by quantum mechanical localization-delocalization transition in the ground state of non-Hermitian single impurity Hatano-Nelson Hamiltonian is underpinned by g…
View article: Witnessing quantum chaos using observational entropy
Witnessing quantum chaos using observational entropy Open
We study observation entropy (OE) for the Quantum kicked top (QKT) model, whose classical counterpart possesses different phases: regular, mixed, or chaotic, depending on the strength of the kicking parameter. We show that OE grows logarit…
View article: One-dimensional L{é}vy Quasicrystal
One-dimensional L{é}vy Quasicrystal Open
Space-fractional quantum mechanics (SFQM) is a generalization of the standard quantum mechanics when the Brownian trajectories in Feynman path integrals are replaced by L{é}vy flights. We introduce L{é}vy quasicrystal by discretizing the s…
View article: Observational entropic study of Anderson localization
Observational entropic study of Anderson localization Open
The notion of the thermodynamic entropy in the context of quantum mechanics is a controversial topic. While there were proposals to refer von Neumann entropy as the thermodynamic entropy, it has it's own limitations. The observational entr…
View article: Geometric quenches in quasidisordered lattice systems
Geometric quenches in quasidisordered lattice systems Open
While global quantum quench has been extensively used in the literature to\nunderstand the localization-delocalization transition for the one-dimensional\nquantum spin chain, the effect of geometric quench (which corresponds to a\nsudden c…
View article: Uncertainty Relation for Non-Hermitian Systems
Uncertainty Relation for Non-Hermitian Systems Open
We construct uncertainty relation for arbitrary finite dimensional PT invariant non-Hermitian quantum systems within a special inner product framework. This construction is led by good observables which are a more general class of operator…
View article: Finite-size scalings in measurement-induced dynamical phase transition
Finite-size scalings in measurement-induced dynamical phase transition Open
Repetitive measurements can cause freezing of dynamics of a quantum state, which is known as quantum Zeno effect. We consider an interacting one-dimensional fermionic system and study the fate of the many-body quantum Zeno transition if th…
View article: Eigenstate entanglement entropy in a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="script">PT</mml:mi></mml:math>-invariant non-Hermitian system
Eigenstate entanglement entropy in a -invariant non-Hermitian system Open
Much has been learned about universal properties of the eigenstate entanglement entropy for one-dimensional lattice models, which is described by a Hermitian Hamiltonian. While very less of it has been understood for non-Hermitian systems.…
View article: Many-body dynamical phase transition in a quasiperiodic potential
Many-body dynamical phase transition in a quasiperiodic potential Open
Much has been learned regarding dynamical quantum phase transition (DQPT) due\nto sudden quenches across quantum critical points in traditional quantum\nsystems. However, not much has been explored when a system undergoes a\nlocalization-d…
View article: Many-body localization in a long-range model: Real-space renormalization-group study
Many-body localization in a long-range model: Real-space renormalization-group study Open
We develop a real-space renormalization-group (RSRG) scheme by appropriately inserting the long-range hopping t∼r^{-α} with nearest-neighbor interaction to study the entanglement entropy and maximum block size for the many-body localizatio…
View article: Many-body dynamics in long-range hopping models in the presence of correlated and uncorrelated disorder
Many-body dynamics in long-range hopping models in the presence of correlated and uncorrelated disorder Open
Much have been learned about universal properties of entanglement entropy\n(EE) and participation ration (PR) for Anderson localization. We find a new\nsub-extensive scaling with system size of the above measures for algebraic\nlocalizatio…
View article: Criterion for the occurrence of many-body localization in the presence of a single-particle mobility edge
Criterion for the occurrence of many-body localization in the presence of a single-particle mobility edge Open
Non-interacting fermions in one dimension can undergo a\nlocalization-delocalization transition in the presence of a quasi-periodic\npotential as a function of that potential. In the presence of interactions,\nthis transition transforms in…
View article: Entanglement production in bosonic systems: Linear and logarithmic growth
Entanglement production in bosonic systems: Linear and logarithmic growth Open
We study the time evolution of the entanglement entropy in bosonic systems\nwith time-independent, or time-periodic, Hamiltonians. In the first part, we\nfocus on quadratic Hamiltonians and Gaussian initial states. We show that all\nquadra…
View article: Quantum adiabatic protocols using emergent local Hamiltonians
Quantum adiabatic protocols using emergent local Hamiltonians Open
We present two applications of emergent local Hamiltonians to speed up quantum adiabatic protocols for isolated noninteracting and weakly interacting fermionic systems in one-dimensional lattices. We demonstrate how to extract maximal work…
View article: Work extraction in an isolated quantum lattice system: Grand canonical and generalized Gibbs ensemble predictions
Work extraction in an isolated quantum lattice system: Grand canonical and generalized Gibbs ensemble predictions Open
We study work extraction (defined as the difference between the initial and the final energy) in noninteracting and (effectively) weakly interacting isolated fermionic quantum lattice systems in one dimension, which undergo a sequence of q…
View article: Integrals of motion for one-dimensional Anderson localized systems
Integrals of motion for one-dimensional Anderson localized systems Open
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, s…
View article: Many-Body Localization in the Presence of a Single-Particle Mobility Edge
Many-Body Localization in the Presence of a Single-Particle Mobility Edge Open
In one dimension, noninteracting particles can undergo a localization-delocalization transition in a quasiperiodic potential. Recent studies have suggested that this transition transforms into a many-body localization (MBL) transition upon…