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

# All

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