Quantum metrology aims to enhance the precision of various measurement tasks
by taking advantages of quantum properties. In many scenarios, precision is not
the sole target; the acquired information must be protected once it is
generated in the sensing process. Considering a remote sensing scenario where a
local site performs cooperative sensing with a remote site to collect private
information at the remote site, the loss of sensing data inevitably causes

Even after almost a century, the foundations of quantum statistical mechanics
are still not completely understood. In this work, we provide a precise account
on these foundations for a class of systems of paradigmatic importance that
appear frequently as mean-field models in condensed matter physics, namely
non-interacting lattice models of fermions (with straightforward extension to
bosons). We demonstrate that already the translation invariance of the
Hamiltonian governing the dynamics and a finite correlation length of the

This paper presents the momentum map structures which emerge in the dynamics
of mixed states. Both quantum and classical mechanics are shown to possess
analogous momentum map pairs. In the quantum setting, the right leg of the pair
identifies the Berry curvature, while its left leg is shown to lead to more
general realizations of the density operator which have recently appeared in
quantum molecular dynamics. Finally, the paper shows how alternative
representations of both the density matrix and the classical density are

A photoelectron forced to pass through two atomic energy levels before
receding from the residual ion shows interference fringes in its angular
distribution as manifestation of a two-slit-type interference experiment in
wave-vector space. This scenario was experimentally realized by irradiating a
Rubidium atom by two low-intensity continuous-wave lasers [Pursehouse et al.,
Phys. Rev. Lett. 122, 053204 (2019)]. In a one-photon process the first laser
excites the 5p level while the second uncorrelated photon elevates the excited

In the high-energy quantum-physics literature one finds statements such as
``matrix algebras converge to the sphere''. Earlier I provided a general
setting for understanding such statements, in which the matrix algebras are
viewed as compact quantum metric spaces, and convergence is with respect to a
quantum Gromov-Hausdorff-type distance. More recently I have dealt with
corresponding statements in the literature about vector bundles on spheres and
matrix algebras. But physicists want, even more, to treat structures on spheres

In this work, a novel method for using a set of electromagnetic quadrupole
fields is presented to implement arbitrary unitary operators on a two-state
quantum system of electrons. In addition to analytical derivations of the
required quadrupole and beam settings which allow an easy direct
implementation, numerical simulations of realistic scenarios show the
feasibility of the proposed setup. This is expected to pave the way not only
for new measurement schemes in electron microscopy and related fields but even

Generating photon pairs via spontaneous parametric down-conversion (SPDC) in
nonlinear crystals is important for a wide range of quantum optics experiments
with spectral properties such as their bandwidths often being a crucial
concern. Here, we show the generic existence of particular phase-matching
conditions in quasi-phase matched KTP, MgO:LN and SLT crystals that lead to
ultra-broadband, widely non-degenerate photon pairs. It is based on the
existence of group-velocity matched, far apart wavelength pairs and for 2 mm

Artificial spiking neural networks have found applications in areas where the
temporal nature of activation offers an advantage, such as time series
prediction and signal processing. To improve their efficiency, spiking
architectures often run on custom-designed neuromorphic hardware, but, despite
their attractive properties, these implementations have been limited to digital
systems. We describe an artificial quantum spiking neuron that relies on the
dynamical evolution of two easy to implement Hamiltonians and subsequent local

This is a tutorial review of methods to braid the world lines of non-Abelian
anyons (Majorana zero-modes) in topological superconductors. That "Holy Grail"
of topological quantum information processing has not yet been reached in the
laboratory, but there now exists a variety of platforms in which one can search
for the Majorana braiding statistics. After an introduction to the basic
concepts of braiding we discuss how one might be able to braid immobile

It has been proved in the context of quantum fields in Minkowski spacetime
that the vacuum state is a thermal state according to uniformly accelerated
observers -- a seminal result known as the Unruh effect. Recent claims,
however, have challenged the validity of this result for extended systems, thus
casting doubts on its physical reality. Here, we study the dynamics of an
extended system, uniformly accelerated in the vacuum. We show that its reduced