# All

## Time dependent coupled harmonic oscillators. (arXiv:1905.08735v1 [quant-ph])

We show that, by using the quantum orthogonal functions invariant, we are
able to solve a coupled of time dependent harmonic oscillators where all the
time dependent frequencies are arbitrary. We do so, by transforming the time
dependent Hamiltonian of the interaction by a set of unitary operators. In
passing, we show that $N$ time dependent and coupled oscillators have a
generalized orthogonal functions invariant from which we can write a
Ermakov-Lewis invariant.

## Entanglement dynamics for circularly accelerated two-level atoms coupled with electromagnetic vacuum fluctuations. (arXiv:1904.10111v2 [quant-ph] UPDATED)

We investigate, in the framework of open quantum systems, the entanglement
dynamics of two circularly accelerated two-level atoms with the same
centripetal acceleration interacting with a bath of fluctuating electromagnetic
fields in the Minkowski vacuum. We assume that the two atoms rotate
synchronically with their separation perpendicular to the rotating plane, and
study the entanglement degradation, creation, revival, and enhancement by
solving the Markovian master equation. In contrast to the scalar-field case,

## Quantum Transport of Rydberg Exciton with Synthetic Spin-Exchange Interactions. (arXiv:1905.08280v1 [quant-ph])

We present a scheme for engineering quantum transport dynamics of spin
excitations in a chain of laser-dressed Rydberg atoms, mediated by synthetic
spin-exchange arising from diagonal van der Waals interaction. The dynamic
tunability and long-range interaction feature of our scheme allows for the
exploration of transport physics unattainable in conventional spin systems. As
two concrete examples, we first demonstrate a topological exciton pumping
protocol that facilitates quantized entanglement transfer, and secondly we

## Entangled States as Robust and Re-usable Carriers of Information. (arXiv:1905.08479v1 [quant-ph])

Entangled states can be used as secure carriers of information much in the
same way as carriers are used in classical communications. In such protocols,
it in safe form at the other end, leaving the carrier intact and ready for
reuse. Furthermore, protocols have been designed for performing quantum state
sharing in this way. In this work, we study the robustness of these protocols

## Multistart Methods for Quantum Approximate Optimization. (arXiv:1905.08768v1 [quant-ph])

Hybrid quantum-classical algorithms such as the quantum approximate
optimization algorithm (QAOA) are considered one of the most promising
approaches for leveraging near-term quantum computers for practical
applications. Such algorithms are often implemented in a variational form,
combining classical optimization methods with a quantum machine to find
parameters to maximize performance. The quality of the QAOA solution depends
heavily on quality of the parameters produced by the classical optimizer.

## Entanglement and non-locality between disparate solid-state quantum memories mediated by photons. (arXiv:1905.08184v2 [quant-ph] UPDATED)

Entangling quantum systems with different characteristics through the
exchange of photons is a prerequisite for building future quantum networks.
Proving the presence of entanglement between quantum memories for light working
at different wavelengths furthers this goal. Here, we report on a series of
experiments with a thulium-doped crystal, serving as a quantum memory for 794
nm photons, an erbium-doped fibre, serving as a quantum memory for
telecommunication-wavelength photons at 1535 nm, and a source of photon pairs

## Quantum parameter-estimation of frequency and damping of a harmonic-oscillator. (arXiv:1905.08288v1 [quant-ph])

We determine the quantum Cram\'er-Rao bound for the precision with which the
oscillator frequency and damping constant of a damped quantum harmonic
oscillator in an arbitrary Gaussian state can be estimated. This goes beyond
standard quantum parameter estimation of a single mode Gaussian state for which
typically a mode of fixed frequency is assumed. We present a scheme through
which the frequency estimation can nevertheless be based on the known results
for single-mode quantum parameter estimation with Gaussian states. Based on

## The squashed entanglement of the noiseless quantum Gaussian attenuator and amplifier. (arXiv:1905.08480v1 [quant-ph])

We determine the maximum squashed entanglement achievable between sender and
receiver of the noiseless quantum Gaussian attenuators and amplifiers, and
prove that it is achieved sending half of an infinitely squeezed two-mode
vacuum state. The key ingredient of the proof is a lower bound to the squashed
entanglement of the quantum Gaussian states obtained applying a two-mode
squeezing operation to a quantum thermal Gaussian state tensored with the
vacuum state. This is the first lower bound to the squashed entanglement of a

## A generalized phase space approach for solving quantum spin dynamics. (arXiv:1905.08782v1 [cond-mat.quant-gas])

Numerical techniques to efficiently model out-of-equilibrium dynamics in
interacting quantum many-body systems are key for advancing our capability to
harness and understand complex quantum matter. Here we propose a new numerical
approach which we refer to as GDTWA. It is based on a discrete semi-classical
phase-space sampling and allows to investigate quantum dynamics in lattice spin
systems with arbitrary $S\geq 1/2$. We show that the GDTWA can accurately

## Contextual advantage for state-dependent cloning. (arXiv:1905.08291v1 [quant-ph])

A number of noncontextual models exist which reproduce different subsets of
quantum theory and admit a no-cloning theorem. Therefore, if one chooses
noncontextuality as one's notion of classicality, no-cloning cannot be regarded
as a nonclassical phenomenon. In this work, however, we show that the
phenomenology of quantum state cloning is indeed nonclassical, but not for the
reasons usually given. Specifically, we focus on the task of state-dependent
cloning and prove that the optimal cloning fidelity predicted by quantum theory