The efficient quantum state reconstruction algorithm described in [P. Six et
al., Phys. Rev. A 93, 012109 (2016)] is experimentally implemented on the
non-local state of two microwave cavities entangled by a circular Rydberg atom.
We use information provided by long sequences of measurements performed by
resonant and dispersive probe atoms over time scales involving the system
decoherence. Moreover, we benefit from the consolidation, in the same
reconstruction, of different measurement protocols providing complementary

Demonstrating a quantum computational speedup is a crucial milestone for
near-term quantum technology. Recently, quantum simulation architectures have
been proposed that have the potential to show such a quantum advantage, based
on commonly made assumptions. The key challenge in the theoretical analysis of
this scheme - as of other comparable schemes such as boson sampling - is to
lessen the assumptions and close the theoretical loopholes, replacing them by

Stimulated emission and absorption are two fundamental processes of
light-matter interaction, and the coefficients of the two processes should be
equal in general. However, we will describe a generic method to realize
significant difference between the stimulated emission and absorption
coefficients of two nondegenerate energy levels, which we refer to as
nonreciprocal transition. As a simple implementation, a cyclic three-level atom
system, comprising two nondegenerate energy levels and one auxiliary energy

The study of memory effects in quantum channels helps in developing
characterization methods for open quantum systems and strategies for quantum
error correction. Two main sets of channels exist, corresponding to system
dynamics with no memory (Markovian) and with memory (non-Markovian).
Interestingly, these sets have a non-convex geometry, allowing one to form a
channel with memory from the addition of memoryless channels and vice-versa.
Here, we experimentally investigate this non-convexity in a photonic setup by

Arrays of atoms trapped in optical tweezers combine features of programmable
analog quantum simulators with atomic quantum sensors. Here we propose
variational quantum algorithms, tailored for tweezer arrays as programmable
quantum sensors, capable of generating entangled states on-demand for precision
metrology. The scheme is designed to generate metrological enhancement by
optimizing it in a feedback loop on the quantum device itself, thus preparing
the best entangled states given the available quantum resources. We apply our

We present a method to map the evolution of photonic random walks that is
compatible with nonclassical input light. Our approach leverages a newly
developed flexible waveguide platform to tune the jumping rate between spatial
modes, allowing the observation of a range of evolution times in a chip of
fixed length. In a proof-of-principle demonstration we reconstruct the
evolution of photons through a uniform array of coupled waveguides by
monitoring the end-face alone. This approach enables direct observation of mode

We derive some entanglement properties of the ground states of two classes of
quantum spin chains described by the Fredkin model, for half-integer spins, and
the Motzkin model, for integer ones. Since the ground states of the two models
are known analytically, we can calculate the entanglement entropy, the
negativity and the quantum mutual information exactly. We show, in particular,
that these systems exhibit long-distance entanglement, namely two disjoint

Normal mode dynamics are ubiquitous underlying the motions of diverse systems
from rotating stars to crystal structures. These behaviors are composed of
simple collective motions of particles which move with the same frequency and
phase, thus encapsulating many-body effects into simple dynamic motions. In
regimes such as the unitary regime for ultracold Fermi gases, a single
collective mode can dominate, leading to simple behavior as seen in
superfluidity. I investigate the evolution of collective motion as a function

We study spin-dipole oscillations of a binary fermionic mixture at nonzero
temperatures. We apply the atomic-orbital method combined with the Monte Carlo
technique based sampling to probe finite temperatures. Our results agree
quantitatively with recent experiment, G. Valtolina et al., Nat. Phys. 13, 704
(2017), showing the appearance of the ferromagnetic phase at stronger repulsion
between components when the temperature is increased.

Recently, it has been demonstrated that asymptotic states of open quantum
system can undergo qualitative changes resembling pitchfork, saddle-node, and
period doubling classical bifurcations. Here, making use of the periodically
modulated open quantum dimer model, we report and investigate a quantum
Neimark-Sacker bifurcation. Its classical counterpart is the birth of a torus
(an invariant curve in the Poincar\'{e} section) due to instability of a limit
cycle (fixed point of the Poincar\'{e} map). The quantum system exhibits a