arXiv subjects

Aitijhya Saha

Publications and source records attributed to Aitijhya Saha.

3 recordsLinked to original sources

arXiv2024

Measurement-Induced Local Dephasing Generates Symmetrically Located Entangled Sites in a Fermionic Tight-Binding Lattice

We investigate an odd-sized fermionic open tight-binding chain subjected to stochastic projective measurements at its central site, effectively inducing localized dephasing. Focusing initially on the single-particle regime, we demonstrate that when the system is prepared in an even-parity state, the dynamics under central-site dephasing drive it toward a nontrivial steady state, which we characterize through both analytical and numerical approaches. Remarkably, this steady state exhibits long-range quantum correlations in the form of symmetrically positioned, pairwise entangled sites across the chain. We further show that the degree of pairwise entanglement can be significantly enhanced by increasing the particle number, provided the system is initialized within a specific symmetry sector associated with an underlying strong symmetry operator. Our results identify a minimal measurement-induced route for generating symmetry-selected long-range pairwise entanglement, with possible implications for quantum communication and distributed quantum information processing.

quant-ph↗

arXiv2024

Stark localization near Aubry-Andr\'e criticality

In this work, we investigate the Stark localization near the Aubry-Andr\'{e} (AA) critical point. We perform careful studies for reporting system-dependent parameters, such as localization length, inverse participation ratio (IPR), and energy gap between the ground and first excited state, for characterizing the localization-delocalization transition. We show that the scaling exponents possessed by these key descriptors of localization are quite different from that of a pure AA model or Stark model. Near the critical point of the AA model, in the presence of Stark field of strength $h$, the localization length $\zeta$ scales as $\zeta\propto h^{-\nu}$ with $\nu\approx0.29$ which is different than both the pure AA model ($\nu=1$) and Stark model ($\nu\approx0.33$). The IPR in this case scales as IPR $\propto h^{s}$ with $s\approx0.096$ which is again significantly different than both the pure AA model ($s\approx0.33$) and Stark model ($s\approx0.33$). The energy gap, $\Delta$, scales as $E\propto h^{\nu z}$, where $z\approx2.37$ which is however same as the pure AA model. Finally, we discuss how invoking a criticality inducing additional control parameter may help in designing better many-body quantum sensors. Quantum critical sensors exploit the venerability of the wavefunction near the quantum critical point against small parameter shifts. By incorporating a control parameter in the form of the quasi-periodic field, i.e., the AA potential, we show a significant advantage can be drawn in estimating an unknown parameter, which is considered here to be the Stark weak field strength, with high precision.

quant-ph↗

arXiv2023

Localization with non-Hermitian off-diagonal disorder

In this work, we discuss a non-Hermitian system described via a one-dimensional single-particle tight-binding model, where the non-Hermiticity is governed by random nearest-neighbour tunnellings, such that the left-to-right and right-to-left hopping strengths are unequal. A physical situation of completely real eigenspectrum arises owing to the Hamiltonian's tridiagonal matrix structure under a simple sign conservation of the product of the conjugate nearest-neighbour tunnelling terms. The off-diagonal disorder leads the non-Hermitian system to a delocalization-localization crossover in finite systems. The emergent nature of the crossover is recognized through a finite-size spectral analysis. The system enters into a localized phase for infinitesimal disorder strength in the thermodynamic limit. We perform a careful scaling analysis of localization length, inverse participation ratio (IPR), and energy splitting and report the corresponding scaling exponents. Noticeably, in contrast to the diagonal disorder, the density of states (DOS) has a singularity at E=0 in the presence of the off-diagonal disorder and the corresponding wavefunction remains delocalized for any given disorder strength.

cond-mat.dis-nn↗