We address the question whether the super-Heisenberg scaling for quantum
estimation is realizable. We unify the results of two approaches. In the first
one, the original system is compared with its copy rotated by the parameter
dependent dynamics. If the parameter is coupled to the one-body part of the
Hamiltonian the precision of its estimation is known to scale at most as
$N^{-1}$ (Heisenberg scaling) in terms of the number of elementary subsystems
used, $N$. The second approach considers fidelity at criticality often leading

Recently it has been demonstrated that an ensemble of trapped ions may serve
as a quantum annealer for the number-partitioning problem [Nature Comm. DOI:
10.1038/ncomms11524]. This hard computational problem may be addressed
employing a tunable spin glass architecture. Following the proposal of the
trapped ions annealer, we study here its robustness against thermal effects,
that is, we investigate the role played by thermal phonons. For the efficient
description of the system, we use a semiclassical approach, and benchmark it

The nonequilibrium quantum dynamics of few boson ensembles which experience a
spatially modulated interaction strength and are confined in finite optical
lattices is investigated. Performing quenches either on the wavevector or the
phase of the interaction profile an enhanced imbalance of the interatomic
repulsion between distinct spatial regions of the lattice is induced. Following
both quench protocols triggers various tunneling channels and a rich excitation

We study the nonlinear dynamics of trapped-ion models far away from the
Lamb-Dicke regime. This nonlinearity induces a sideband cooling blockade,
stopping the propagation of quantum information along the Hilbert space of the
Jaynes-Cummings and quantum Rabi models. We compare the linear and nonlinear
cases of these models in the ultrastrong and deep strong coupling regimes.
Moreover, we propose a scheme that simulates the nonlinear quantum Rabi model
in all coupling regimes. This can be done via off-resonant nonlinear red and

Stokes phenomenon refers to the fact that the asymptotic expansion of complex
functions can differ in different regions of the complex plane, and that beyond
the so-called Stokes lines has an unphysical divergence. An important special
case is when the Stokes lines emanate from phase space caustics of a complex
trajectory manifold. In this case, symmetry determines that to second order
there is a double coverage of the space, one portion of which is unphysical.

Quantum simulators have the exciting prospect of giving access to real-time
dynamics of lattice gauge theories, in particular in regimes that are difficult
to compute on classical computers. Future progress towards scalable quantum
simulation of lattice gauge theories, however, hinges crucially on the
efficient use of experimental resources. As we argue in this work, due to the
fundamental non-uniqueness of discretizing the relativistic Dirac Hamiltonian,

Quantum effects, prevalent in the microscopic scale, generally elusive in
macroscopic systems due to dissipation and decoherence. Quantum phenomena in
large systems emerge only when particles are strongly correlated as in
superconductors and superfluids. Cooperative interaction of correlated atoms
with electromagnetic fields leads to superradiance, the enhanced quantum
radiation phenomenon, exhibiting novel physics such as quantum Dicke phase and
ultranarrow linewidth for optical clocks. Recent researches to imprint atomic

We analyze the second-order photon autocorrelation function $g^{(2)}$ with
respect to the photon probability distribution and discuss the generic features
of a distribution that result in superthermal photon bunching ($g^{(2)}>2$).
Superthermal photon bunching has been reported for a number of optical
microcavity systems that exhibit processes like superradiance or mode
competition. We show that a superthermal photon number distribution cannot be
constructed from the principle of maximum entropy, if only the intensity and

We report on the coupling of the emission from a single europium-doped
nanocrystal to a fiber-based microcavity under cryogenic conditions. As a first
step, we study the sample properties and observe a strong correlation between
emission lifetime and brightness, as well as a lifetime reduction for
nanocrystals embedded in a polymer film. This is explained by differences in
the local density of states. We furthermore quantify the scattering loss of a
nanocrystal inside the cavity and use this to deduce the crystal size. Finally,

It is shown that a linearized classical gravity wave $\hat{a}$ {\em la}
Einstein can get entangled with an array of test masses in a plane
perpendicular to its direction of propagation. A Bell-CHSH inequality based on
the requirement of noncontextuality for classical realism is derived, and it is
shown that the entangled state produced violates this inequality.