45 research outputs found
Entanglement dynamics following a sudden quench: an exact solution
We present an exact and fully analytical treatment of the entanglement
dynamics for an isolated system of coupled oscillators following a sudden
quench of the system parameters. The system is analyzed using the solutions of
the time dependent Schrodinger's equation, which are obtained by solving the
corresponding nonlinear Ermakov equations. The entanglement entropies exhibit a
multi-oscillatory behaviour, where the number of dynamically generated time
scales increases with . The harmonic chains exhibit entanglement revival and
for larger values of , we find near-critical logarithmic scaling for
the entanglement entropy, which is modulated by a time dependent factor. The
case is equivalent to the two site Bose-Hubbard model in the tunneling
regime, which is amenable to empirical realization in cold atom systems.Comment: Figure for large N added, discussion related with near critical
scaling behavior adde
Sunburst quantum Ising model under interaction quench: entanglement and role of initial state coherence
We study the non-equilibrium dynamics of an isolated bipartite quantum
system, the sunburst quantum Ising model, under interaction quench. The
pre-quench limit of this model is two non-interacting integrable systems,
namely a transverse ising chain and finite number of isolated qubits. As a
function of interaction strength, the spectral fluctuation property goes from
Poisson to Wigner-Dyson statistics. We chose entanglement entropy as a probe to
study the approach to thermalization or lack of it in post-quench dynamics. In
the near-integrable limit, as expected, the linear entropy displays oscillatory
behavior while in the chaotic limit, it saturates. Along with the chaotic
nature of the time evolution generator, we show the importance of the role
played by the coherence of the initial state in deciding the nature of
thermalization. We further show that these findings are general by replacing
the Ising ring with a disordered model with disorder strength putting it
in the many-body localized phase
Universal transition of spectral fluctuation in particle-hole symmetric system
We study the spectral properties of a multiparametric system having
particle-hole symmetry in random matrix setting. We observe a crossover from
Poisson to Wigner-Dyson like behavior in average local ratio of spacing within
a spectrum of single matrix as a function of effective single parameter
referred to as complexity parameter. The average local ratio of spacing varies
logarithmically in complexity parameter across the transition. This behavior is
universal for different ensembles subjected to same matrix constraint like
particle-hole symmetry. The universality of this dependence is further
established by studying interpolating ensemble connecting systems with
particle-hole symmetry to that with chiral symmetry. For each interpolating
ensemble the behavior remains logarithmic in complexity parameter. We verify
this universality of spectral fluctuation in case of a 2D Su-Schrieffer-Heeger
(SSH) like model along with the logarithmic dependence on complexity parameter
for ratio of spacing during transition from integrable to non-integrable limit
Unbounded quantum backflow in two dimensions
Quantum backflow refers to the counterintuitive fact that the probability can
flow in the direction opposite to the momentum of a quantum particle. This
phenomenon has been seen to be small and fragile for one-dimensional systems,
in which the maximal amount of backflow has been found to be bounded. Quantum
backflow exhibits dramatically different features in two-dimensional systems
that, contrary to the one-dimensional case, allow for degenerate energy
eigenstates. Here we investigate the case of a charged particle that is
confined to move on a finite disk punctured at the center and that is pierced
through the center, and normally to the disk, by a magnetic flux line. We
demonstrate that quantum backflow can be unbounded (in a certain sense), which
makes this system a promising physical platform regarding the
yet-to-be-performed experimental observation of this fundamental quantum
phenomenon.Comment: 11 pages, 1 figur