2,699 research outputs found
Signatures of many-body localization in steady states of open quantum systems
Many-body localization (MBL) is a result of the balance between
interference-based Anderson localization and many-body interactions in an
ultra-high dimensional Fock space. It is usually expected that dissipation is
blurring interference and destroying that balance so that the asymptotic state
of a system with an MBL Hamiltonian does not bear localization signatures. We
demonstrate, within the framework of the Lindblad formalism, that the system
can be brought into a steady state with non-vanishing MBL signatures. We use a
set of dissipative operators acting on pairs of connected sites (or spins), and
show that the difference between ergodic and MBL Hamiltonians is encoded in the
imbalance, entanglement entropy, and level spacing characteristics of the
density operator. An MBL system which is exposed to the combined impact of
local dephasing and pairwise dissipation evinces localization signatures
hitherto absent in the dephasing-outshaped steady state.Comment: 6 pages, 3 figure
Photon waiting time distributions: a keyhole into dissipative quantum chaos
Open quantum systems can exhibit complex states, which classification and
quantification is still not well resolved. The Kerr-nonlinear cavity,
periodically modulated in time by coherent pumping of the intra-cavity photonic
mode, is one of the examples. Unraveling the corresponding Markovian master
equation into an ensemble of quantum trajectories and employing the recently
proposed calculation of quantum Lyapunov exponents [I.I. Yusipov {\it et al.},
Chaos {\bf 29}, 063130 (2019)], we identify `chaotic' and `regular' regimes
there. In particular, we show that chaotic regimes manifest an intermediate
power-law asymptotics in the distribution of photon waiting times. This
distribution can be retrieved by monitoring photon emission with a
single-photon detector, so that chaotic and regular states can be discriminated
without disturbing the intra-cavity dynamics.Comment: 7 pages, 5 figure
Influence of topological excitations on Shapiro steps and microwave dynamical conductance in bilayer exciton condensates
The quantum Hall state at total filling factor in bilayer systems
realizes an exciton condensate and exhibits a zero-bias tunneling anomaly,
similar to the Josephson effect in the presence of fluctuations. In contrast to
conventional Josephson junctions, no Fraunhofer diffraction pattern has been
observed, due to disorder induced topological defects, so-called merons. We
consider interlayer tunneling in the presence of microwave radiation, and find
Shapiro steps in the tunneling current-voltage characteristic despite the
presence of merons. Moreover, the Josephson oscillations can also be observed
as resonant features in the microwave dynamical conductance
Dynamic equations for three different qudits in a magnetic field
A closed system of equations for the local Bloch vectors and spin correlation
functions of three magnetic qudits, which are in an arbitrary, time-dependent,
external magnetic field, is obtained using decomplexification of the
Liouville-von Neumann equation. The algorithm of the derivation of the dynamic
equations is presented. In the basis convenient for the important physical
applications structure constants of algebra su(2S+1) are calculated.Comment: 11 page
Control of a single-particle localization in open quantum systems
We investigate the possibility to control localization properties of the
asymptotic state of an open quantum system with a tunable synthetic
dissipation. The control mechanism relies on the matching between properties of
dissipative operators, acting on neighboring sites and specified by a single
control parameter, and the spatial phase structure of eigenstates of the system
Hamiltonian. As a result, the latter coincide (or near coincide) with the dark
states of the operators. In a disorder-free Hamiltonian with a flat band, one
can either obtain a localized asymptotic state or populate whole flat and/or
dispersive bands, depending on the value of the control parameter. In a
disordered Anderson system, the asymptotic state can be localized anywhere in
the spectrum of the Hamiltonian. The dissipative control is robust with respect
to an additional local dephasing.Comment: 6 pages, 5 figure
- …