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Topological quantum states have been proposed and investigated on
two-dimensional flat surfaces or lattices with different geometries like the
plane, cylinder and torus. Here, we study quantum anomalous Hall (QAH) or Chern
insulator (CI) states on two-dimensional singular surfaces (such as conical and
helicoid-like surfaces). Such singular geometries can be constructed based on
the disk geometry and a defined unit sector with $n$-fold rotational symmetry.

Superconducting nanowire single photon detectors (SNSPDs) have advanced
various frontier scientific and technological fields such as quantum key
distribution and deep space communications. However, limited by available
cooling technology, all past experimental demonstrations have had ground-based
applications. In this work we demonstrate a SNSPD system using a hybrid
cryocooler compatible with space applications. With a minimum operational
temperature of 2.8 K, this SNSPD system presents a maximum system detection

Electron paramagnetic resonance (EPR) spectroscopy is an important technology
in physics, chemistry, materials science, and biology. Sensitive detection with
a small sample volume is a key objective in these areas, because it is crucial,
for example, for the readout of a highly packed spin based quantum memory or
the detection of unlabeled metalloproteins in a single cell. In conventional
EPR spectrometers, the energy transfer from the spins to the cavity at a

Occupying a position between entanglement and Bell nonlocality,
Einstein-Podolsky-Rosen (EPR) steering has attracted increasing attention in
recent years. Many criteria have been proposed and experimentally implemented
to characterize EPR-steering. Nevertheless, only a few results are available to
quantify steerability using analytical results. In this work, we propose a
method for quantifying the steerability in two-qubit quantum states in the
two-setting EPR-steering scenario, using the connection between joint

Strong coupling between light and matter is possible with a variety of
organic materials. In contrast to the simpler inorganic case, organic materials
often have a complicated spectrum, with vibrationally dressed electronic
transitions. Strong coupling to light competes with this vibrational dressing,
and if strong enough, can suppress the entanglement between electronic and
vibrational degrees of freedom. By exploiting symmetries, we can perform exact
numerical diagonalization to find the polaritonic states for intermediate

We study systematically resource measures of coherence and entanglement based
on R\'enyi relative entropies, which include the logarithmic robustness of
coherence, geometric coherence, and conventional relative entropy of coherence
together with their entanglement analogues. First, we show that each R\'enyi
relative entropy of coherence is equal to the corresponding R\'enyi relative
entropy of entanglement for any maximally correlated state. By virtue of this

We investigate quantum teleportation of ensembles of coherent states of light
with a Gaussian distributed displacement in phase space. Recently, the
following general question has been addressed in [P. Liuzzo-Scorpo et al.,
arXiv:1705.03017]: Given a limited amount of entanglement and mean energy
available as resources, what is the maximal fidelity that can be achieved on
average in the teleportation of such an alphabet of states? Here, we consider a

We study the steady state of two coupled two-level atoms interacting with a
non-equilibrium environment that consists of two heat baths at different
temperatures. Specifically, we analyze four cases with respect to the
configuration about the interactions between atoms and heat baths. Using
secular approximation, the conventional master equation usually neglects
steady-state coherence, even when the system is coupled with a non-equilibrium
environment. When employing the master equation with no secular approximation,

The ability to distribute quantum entanglement over long distances is a vital
ingredient for quantum technologies. Single atoms and atom-like defects in
solids are ideal quantum light sources and quantum memories to store
entanglement. However, a major obstacle to developing long-range quantum
networks is the mismatch between typical atomic transition energies in the
ultraviolet and visible spectrum, and the low-loss propagation band of optical
fibers in the infrared, around 1.5 $\mu$m. A notable exception is the Er$^{3+}$

We review recent results on the simulation of quantum channels, the reduction
of adaptive protocols (teleportation stretching), and the derivation of
converse bounds for quantum and private communication, as established in PLOB
[Pirandola, Laurenza, Ottaviani, Banchi, arXiv:1510.08863]. We start by
introducing a general weak converse bound for private communication based on
the relative entropy of entanglement. We discuss how combining this bound with