We implement a quantum error correction algorithm for bit-flip errors on the
topological toric code using deep reinforcement learning. An action-value
Q-function encodes the discounted value of moving a defect to a neighboring
site on the square grid (the action) depending on the full set of defects on
the torus (the syndrome or state). The Q-function is represented by a deep
convolutional neural network. Using the translational invariance on the torus
allows for viewing each defect from a central perspective which significantly

The evolution of quantum light through linear optical devices can be
described by the scattering matrix $S$ of the system. For linear optical
systems with $m$ possible modes, the evolution of $n$ input photons is given by
a unitary matrix $U=\varphi_{m,M}(S)$ given by a known homomorphism,
$\varphi_{m,M}$, which depends on the size of the resulting Hilbert space of
the possible photon states, $M$. We present a method to decide whether a given
unitary evolution $U$ for $n$ photons in $m$ modes can be achieved with linear

Understanding and controlling collisions is crucial to the burgeoning field
of ultracold molecules. All experiments so far have observed fast loss of
molecules from the trap. However, the dominant mechanism for collisional loss
is not well understood when there are no allowed 2-body loss processes. Here we
experimentally investigate collisional losses of nonreactive ultracold RbCs
molecules, and compare our findings with the sticky collision hypothesis that

We introduce diffraction-based interaction-free measurements. In contrast
with previous work where a set of discrete paths is engaged, good quality
interaction-free measurements can be realized with a continuous set of paths,
as is typical of optical propagation. If a bomb is present in a given spatial
region -- so sensitive that a single photon will set it off -- its presence can
still be detected without exploding it. This is possible because, by not

Work in isolated systems, defined by the two projective energy measurement
scheme, is a random variable whose the distribution function obeys the
celebrated fluctuation theorems of Crooks and Jarzynski. In this study, we
provide a simple way to calculate the work distribution associated to sudden
quench processes in a given class of quantum many-body systems. Due to the
large Hilbert space dimension of these systems, we show that there is an energy
coarse-grained description of the exact work distribution that can be

Imaging with quantum states of light promises advantages over classical
approaches in terms of resolution, signal-to-noise ratio and sensitivity.
However, quantum detectors are particularly sensitive sources of classical
noise that can reduce or cancel any quantum advantage in the final result.
Without operating in the single-photon counting regime, we experimentally
demonstrate distillation of a quantum image from measured data composed of a
superposition of both quantum and classical light. We measure the image of an

Weyl photons appear when two three-dimensional photonic bands with linear
dispersion are degenerate at a single momentum point, labeled as Weyl point.
These points have remarkable properties such as being robust topological
monopoles of Berry curvature as well as an associated vanishing density of
states. Here, we study the quantum optical consequences of such topological
Weyl photons by characterizing the individual and collective dynamics of
quantum emitters close to resonance with these points. Using an exact

Although it may seem The Delayed Choice experiments contradict causality and
one could construct an experiment which could possibly affect the past, using
Many World interpretation we prove it is not possible. We also find a
mathematical background to Which-path information and show why its
obtainability prevents system from interfering. We find a system which exhibit
both interference and correlation and show why one-particle interference and
correlations are complementary. Better visible interference pattern leads to

An initial coherent state is propagated exactly by a kicked quantum
Hamiltonian and its associated classical stroboscopic map. The classical
trajectories within the initial state are regular for low kicking strengths,
then bifurcate and become mainly chaotic as the kicking parameter is increased.
Time-evolution is tracked using classical, quantum and semiclassical Wigner
functions, obtained via the Herman-Kluk propagator. Quantitative comparisons
are also included and carried out from probability marginals and

There is a remarkable characteristic of photosynthesis in nature, that is,
the energy transfer efficiency is close to 100%. Recently, due to the rapid
progress made in the experimental techniques, quantum coherent effects have
been experimentally demonstrated. Traditionally, the incoherent theories are
capable of calculating the energy transfer efficiency, e.g., (generalized)
F\"orster theory and modified Redfield theory. However, in order to describe